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LC classics problems
- Blind Curated 75
- Grind 75
- Grind 169
- LC 官神Github題目分類整理
- LC top 100 likes
- neetcode 150 LC list
- jiakaobo LC : LC code & video
- LC pattern @ blind : Curated-List-of-Top-100-LeetCode-Questions-to-Save-Your-Time
- LC Algorithm Problem Classification
- cheatsheet-leetcode-a4
- 14-patterns-to-ace-any-coding-interview-question
- grokking-the-coding-interview
LC experiences
- LC難度表
- 數字越高, 題目越難, 挑與自己LC排名接近的題庫
- (e.g. LC rank ~= 1600, pick 1600 problem)
- 代碼隨想錄
- Leetcode cookbook
- fucking-algorithm
- fucking-algorithm website
- FAANG 面試準備經驗與建議（一）
- FAANG 面試準備經驗與建議（二）
- LC 小知識
- Meta SWE isnterview prep
- 0到100的軟體工程師面試之路
- 來和大家聊聊我是如何刷題的 : pt1, pt2, pt3
- LC難度表
LC Flow
- high level idea : data structure, algorithm
- offer time & space complexity
- code implementation
- offer test case (consider edge case)
- discussion & follow up
- Resource.md -
Resourcefor coding interview (keep updating) - Teach yourself CS
- MindMapCodeInterview - Mind map for coding interview
- CodeInterviewCheatsheet - Coding interview cheetsheet
- repl.it - Coding online!
- Visualization
- Algorithms viz
- visualgo - DFS / BFS - DFS, BFS visualization
- visualgo - linkedlist - Linkedlist visualization
- visualgo - BST - binary search tree visualization
- toptal-sorting-algorithms- sorting algorithms online
- How to: Work at Google — Example Coding/Engineering Interview
- bit_manipulation.md - Bit Manipulation Cheat Sheet
- Py TimeComplexity - Py basic data structure
Time Complexityref - Py data model - Python data model doc
- pgexercises - Postgre exercises
- sqlservertutorial
- Books
- freecodecamp - data-structures
- LC interview-experience
- Cheatsheet
Data structure
System design
Tools
LC SQL resources
- Bit Manipulation
- Array
- String
- Linked List
- Stack
- Queue
- Heap
- Tree
- Hash Table
- Math
- Two Pointers
- Sort
- Recursion
- Binary Search
- Binary Search Tree
- Breadth-First Search
- Depth-First Search
- Backtracking
- Dynamic Programming
- Greedy
- Graph
- Geometry
- Simulation
- Design
- Concurrency
| # | Title | Solution | Use case | Comment | Status |
|---|---|---|---|---|---|
Linear | |||||
| Array | Py | AGAIN* | |||
| Queue | Py,JS | AGAIN* | |||
| Stack | Py,JS (linkedlist),JS (array) | OK | |||
| Hash table | Py,JS | usually for improvingtime complexity B(O) via extra space complexity (time-space tradeoff) | good basic | AGAIN**** | |
Linear, Pointer | |||||
| LinkedList | Py,JS,Java | OK** | |||
| Doubly LinkedList | Python,JS | AGAIN | |||
Non Linear, Pointer | |||||
| Tree | Py | AGAIN** | |||
| Binary search Tree (BST) | Python,JS,Java | AGAIN | |||
| Binary Tree | Py | AGAIN** | |||
| Trie | Py | AGAIN | |||
| Heap | heap.py,MinHeap.py,MaxHeap.py,MinHeap.java,MaxHeap.java | AGAIN | |||
| Priority Queue (PQ) | Py 1,Py 2,Py 3 | AGAIN | |||
Graph | |||||
| Graph | Py,JS.Java1,Java2 | OK*** | |||
| DirectedEdge | Java | AGAIN |
| # | Title | Solution | Use case | Comment | Time complexity | Space complexity | Status |
|---|---|---|---|---|---|---|---|
| Binary search | Python | complexity ref | Best : O(1), Avg : O(log N), Worst : O(log N) | AGAIN | |||
| Linear search | Python | AGAIN | |||||
| Breadth-first search (BFS) | Python | FIND SHORTEST PATH | AGAIN*** | ||||
| Depth-first search (DFS) | Python | TO CHECK IF SOMETHING EXIST | inorder,postorder,postorder (can recreate a tree) | AGAIN*** | |||
| Bubble sort | Python | OK* (3) | |||||
| Insertion sort | Python,InsertionSort.java | stable sort | work very fast fornearly sorted array | Best :O(n), Average : O(n^2), Worst : O(n^2) | Worst : O(1) | AGAIN | |
| Bucket sort | Python,BucketSort.java | AGAIN | |||||
| Quick sort | quick_sort.py,quick_sort_v2.py,QuickSort.java,QuickSortV2.java,QuickSortV3.java | NOTE !!!,avg is NLogN, worst is N**2,big O ref,big O ref 2 | Best : O(N Log N), Avg : O(N Log N), Worst : O(N^2) | AGAIN*** | |||
| Heap sort | Python | big O ref | Best : O(N Log N), Avg : O(N Log N), Worst : O(N Log N) | AGAIN** | |||
| Merge sort | merge_sort_topdown.py,mergesort_bottomup.py,MergeSortTopDown.java,MergeSort.javaSQL | Best : O(N Log N), Avg : O(N Log N), Worst : O(N Log N) | O(N) | OK* (2) | |||
| Pancake sort | Python | AGAIN | |||||
| Selection sort | Python,JS | AGAIN | |||||
| Topological sort | Python,Java,Java V2 | Topological Sort is a algorithm can find "ordering" on an "order dependency" graph | AGAIN | ||||
| md5 | Python | AGAIN | |||||
| Union Find | Python 1,Python 2,Java 1,Java 2,Java 3 | AGAIN | |||||
| Dynamic programming | JS 1,fibonacci_dp JS | AGAIN | |||||
| Dijkstra | Python,Java 1,Java 2 | AGAIN*** | |||||
| Floyd-Warshall | Python | not start | |||||
| Bellman-Ford | Python | not start | |||||
| Quick Find | Python,Java | init : O(N), union : O(N), find : O(1) | simple, but slow | AGAIN | |||
| Quick Union | Java,Java v2 | init : O(N), union : O(N), find : O(N) | lazy approach, route compression, optimized Quick Find | AGAIN | |||
| Quick Union (Improvements) | lazy approach, path compression | AGAIN | |||||
Priority Queue (unsorted) | Java | AGAIN | |||||
| LRU cache | Python | LC 146 | AGAIN | ||||
| LFU Cache | Python | LC 460 | AGAIN | ||||
| DifferenceArray | Java | LC 1109, 370 | AGAIN | ||||
| Kadane Algo | Java | LC 53, 152,918 | AGAIN |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 015 | 3 Sum | Python,Java | O(n^2) | O(1) | Medium | Curated Top 75, good basic, check with# 001 Two Sum,#018 4 sum,Two Pointers,good basic,amazon,fb | OK******* (7) |
| 016 | 3 Sum Closest | Python | O(n^2) | O(1) | Medium | Two Pointers,basic,good trick,3 sum,google, fb, apple, m$, GS, amazon | AGAIN**** (2) |
| 018 | 4 Sum | Python | O(n^3) | O(1) | Medium | k sum,Two Pointers, check#016 3 sum,# 454 4 SUM II,good trick,fb | AGAIN******** (4) |
| 026 | Remove Duplicates from Sorted Array | Python,Scala,Java | O(n) | O(1) | Easy | MUST,Two Pointers,basic,good trick,M$ ,fb | AGAIN************** (11) |
| 027 | Remove Element | Python,Java | O(n) | O(1) | Easy | MUST,2 pointers,amazon | OK* (2) |
| 031 | Next Permutation | Python,Scala,Java | O(n) | O(1) | Medium | good trick, check, 2 pointers, Uber, GS,google,amazon,fb | AGAIN****************** (8) (MUST) |
| 041 | First Missing Positive | Python,Java | O(n) | O(1) | Hard | good trick, hash key , array, LC top 100 like,amazon,fb, google, apple, uber | OK** (2) |
| 048 | Rotate Image | Python,Java | O(n^2) | O(1) | Medium | Curated Top 75,basic,i,j->j,itranspose matrix, garena,amazon,apple | AGAIN************* (5) (MUST) |
| 054 | Spiral Matrix | Python,Java | O(m * n) | O(1) | Medium | Curated Top 75, good basic, array boundary, matrix,amazon | AGAIN**** (4) |
| 057 | Insert Interval | Python,Java | Medium | Curated Top 75, good basic,056 Merge Intervals, java array, list basic | AGAIN********** (5) (MUST!) | ||
| 059 | Spiral Matrix II | Python | O(n^2) | O(1) | Medium | check# 054 Spiral Matrix,amazon | AGAIN** (2) |
| 066 | Plus One | Python,Java | O(n) | O(1) | Easy | basic,digit,google | AGAIN** (3) |
| 073 | Set Matrix Zeroes | Python,Java | O(m * n) | O(1) | Medium | Curated Top 75,matrix,amazon | OK* (4) |
| 080 | Remove Duplicates from Sorted Array II | Python,Java | O(n) | O(1) | Medium | two pointers,AGAIN,basic,trick,fb,#26 Remove Duplicates from Sorted Array | AGAIN************ (8) |
| 118 | Pascal's Triangle | Python | O(n^2) | O(1) | Easy | trick,basic | AGAIN** (2) |
| 119 | Pascal's Triangle II | Python | O(n^2) | O(1) | Easy | array, check with# 118 Pascal's Triangle,amazon | OK** (4) |
| 121 | Best Time to Buy and Sell Stock | Python,Java | O(n) | O(1) | Easy | Curated Top 75,dp,basic,greedy,UBER,M$,amazon,fb | OK****** (7) (but again) |
| 157 | Read N Characters Given Read4 | Python | O(n) | O(1) | Easy | 🔒, buffer,google,amazon,fb | AGAIN**** (3) |
| 163 | Missing Ranges | Python,Java | O(n) | O(1) | Medium | two pointer, 🔒,google,amazon | OK******* (4) |
| 169 | Majority Element | Python,Java | O(n) | O(1) | Easy | amazon | OK* |
| 189 | Rotate Array | Python,Java | O(n) | O(1) | Medium | array, k % len(nums), good basic,amazon | OK* (7) (but again) |
| 209 | Minimum Size Subarray Sum | Python,Java | O(n) | O(1) | Medium | good basic, sliding window,Binary Search,trick,2 pointers,fb | OK********** (7) (but again) |
| 215 | Kth Largest Element in an Array | Python,Java | O(n) ~O(n^2) | O(1) | Medium | EPI,quick sort, bubble sort, sort,amazon,fb | OK* (2) |
| 228 | Summary Ranges | Python,Java | O(n) | O(1) | Easy | check# 163 Missing Ranges,basic, array,google | OK*** (4) |
| 229 | Majority Element II | Python,Java | O(n) | O(1) | Medium | OK | |
| 238 | Product of Array Except Self | Python,Java | O(n) | O(1) | Medium | Curated Top 75, left, right array, LintCode,good trick,Apple,M$,amazon,fb | OK******* (but again)(6) |
| 240 | Search a 2D Matrix II | Python | O(m + n) | O(1) | Medium | LintCode,basic,matrix,trick,binary search, check# 74 Search a 2D Matrix,amazon,apple | OK***** (7) (but again) |
| 243 | Shortest Word Distance | Python,Java | O(n) | O(1) | Easy | 🔒,basic | OK* |
| 245 | Shortest Word Distance III | Python | O(n) | O(1) | Medium | 🔒, checkShortest Word Distance I II III | OK* |
| 251 | Flatten 2D Vector | Python,Java | O(1) | O(1) | Medium | 🔒,good basic, check# 341 Flatten Nested List Iterator,google,airbnb,twitter,amazon | AGAIN******** (4) |
| 277 | Find the Celebrity | Python | O(n) | O(1) | Medium | graph, 🔒,fb,amazon,trick | AGAIN********** (5) |
| 287 | Find the Duplicate Number | Python,Java | Medium | good trick,binary search, cycle linked list, check# 142 Linked List Cycle II,amazon | OK* (2) | ||
| 289 | Game of Life | Python | O(m * n) | O(1) | Medium | simultaneous,matrix,complex,google,amazon | AGAIN*** (4) |
| 293 | Flip Game | Python | O(n * (c+1)) | O(1) | Easy | 🔒,basic | AGAIN* |
| 308 | Range Sum Query 2D - Mutable | Python | O(n * (c+1)) | O(1) | Hard | LC 303, pre-sum, matrix, tree, 🔒,google | not start |
| 311 | Sparse Matrix Multiplication | Python,Java | O(m * n * l) | O(m * l) | Medium | 🔒, matrix,basic,fb,google | OK**** (5) |
| 334 | Increasing Triplet Subsequence | Python,Java | O(n) | O(1) | Medium | AGAIN, check# 300 Longest Increasing Subsequence,trick,fb, google | OK***** (but again) (4) |
| 335 | Self Crossing | Java | O(n) | O(1) | Hard | Array, geometry, google | Again (not start) |
| 370 | Range Addition | Python,Java | O(k + n) | O(1) | Medium | prefix, diff array, check# 598 Range Addition II,amazon, LC 1109, LC 1094, google | AGAIN************** (4) (MUST) |
| 384 | Shuffle an Array | Python | O(n) | O(n) | Medium | EPI,trick | OK* |
| 396 | Rotate Function | Python | O(n) | O(1) | Medium | can pass, math,trick,amazon | AGAIN*** (3) |
| 412 | Fizz Buzz | Python,Scala | O(n) | O(1) | Easy | OK | |
| 414 | Third Maximum Number | Python | O(n) | O(1) | Easy | good basic,amazon | OK* (4) |
| 419 | Battleships in a Board | Python | O(m * n) | O(1) | Medium | AGAIN* | |
| 422 | Valid Word Square | Python | O(m * n) | O(1) | Easy | 🔒,basic,matrix | AGAIN* |
| 442 | Find All Duplicates in an Array | Python | O(n) | O(1) | Medium | OK* | |
| 448 | Find All Numbers Disappeared in an Array | Python | O(n) | O(1) | Easy | OK | |
| 498 | Diagonal Traverse | Python,Java | O(n) | O(1) | Medium | matrix,google,fb | AGAIN*** (4) |
| 531 | Lonely Pixel I | Python | O(m * n) | O(m + n) | Medium | 🔒,matrix,basic | AGAIN* |
| 533 | Lonely Pixel II | Python | O(m * n) | O(m * n) | Medium | 🔒 | AGAIN (not start*) |
| 565 | Array Nesting | Python | O(n) | O(1) | Medium | union find,dfs,apple | AGAIN**** (1) |
| 566 | Reshape the Matrix | Python | O(m * n) | O(m * n) | Easy | basic,matrix | AGAIN** |
| 581 | Shortest Unsorted Continuous Subarray | Python | O(n) | O(1) | Easy | basic | AGAIN* |
| 605 | Can Place Flowers | Python | O(n) | O(1) | Easy | pass vs continue | OK* |
| 624 | Maximum Distance in Arrays | Python | O(n) | O(1) | Easy | 🔒 | AGAIN* |
| 643 | Maximum Average Subarray I | Python | O(n) | O(1) | Easy | Math,basic | AGAIN* |
| 661 | Image Smoother | Python | O(m * n) | O(1) | Easy | matrix,basic,amazon | OK***** (4) (but again!) |
| 665 | Non-decreasing Array | Python | O(n) | O(1) | Easy | AGAIN (not start) | |
| 667 | Beautiful Arrangement II | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 670 | Maximum Swap | Python | O(logn) | O(logn) | Medium | good basic, reversed, str -> list,string + pointers ,fb | AGAIN************ (9) (MUST) |
| 674 | Longest Continuous Increasing Subsequence | Python,Java | O(n) | O(1) | Easy | good basic,dp,2 pointers ,array ,fb | OK*** (5) |
| 697 | Degree of an Array | Python | O(n) | O(n) | Easy | AGAIN (not start) | |
| 713 | Subarray Product Less Than K | Python | O(n) | O(1) | Medium | basic,sliding window, good trick | OK****** (3) (but again) |
| 717 | 1-bit and 2-bit Characters | Python | O(n) | O(1) | Easy | Greedy | AGAIN (not start) |
| 723 | Candy Crush | Python | O((R * C)^2) | O(1) | Medium | complex | AGAIN (not start) |
| 724 | Find Pivot Index | Python | O(n) | O(1) | Easy | OK* | |
| 729 | My Calendar I | Python,Java | O(nlogn) | O(n) | Medium | good basic, brute force, binary search, google | AGAIN**** (1) |
| 731 | My Calendar II | Python,Java | O(n^2) | O(n) | Medium | trick, good trick, scanning line, google, | AGAIN******** (4) |
| 747 | Largest Number At Least Twice of Others | Python | O(n) | O(1) | Easy | good basic,data structure | OK* |
| 755 | Pour Water | Python | O(v * n) | O(1) | Medium | complex | AGAIN (not start) |
| 766 | Toeplitz Matrix | Python | O(m * n) | O(1) | Easy | basic,matrix,google | AGAIN* (2) |
| 769 | Max Chunks To Make Sorted | Python,Java | O(n) | O(1) | Medium | good trick, prefix sum, stack, array, google | AGAIN*** (1) |
| 792 | Number of Matching Subsequences | Python,Java | O(n + w) | O(1) | Medium | basic, hash map, google | AGAIN**** (2) |
| 794 | Valid Tic-Tac-Toe State | Python | O(1) | O(1) | Medium | complex | AGAIN |
| 795 | Number of Subarrays with Bounded Maximum | Python | O(n) | O(1) | Medium | AGAIN (not start*) | |
| 807 | Max Increase to Keep City Skyline | Python | O(n^2) | O(n) | Medium | AGAIN* | |
| 821 | Shortest Distance to a Character | Python | O(n) | O(1) | Easy | basic,trick | AGAIN** |
| 830 | Positions of Large Groups | Python | O(n) | O(1) | Easy | basic | AGAIN* |
| 832 | Flipping an Image | Python | O(n^2) | O(1) | Easy | AGAIN* | |
| 835 | Image Overlap | Python | O(n^4) | O(n^2) | Medium | AGAIN (not start) | |
| 840 | Magic Squares In Grid | Python | O(m * n) | O(1) | Easy | complex | AGAIN (not start) |
| 842 | Split Array into Fibonacci Sequence | Python | O(n^3) | O(n) | Medium | check# 306 Addictive Number,basic,dfs,fibonacci | AGAIN* (not start) |
| 845 | Longest Mountain in Array | Python | O(n) | O(1) | Medium | basic,trick | AGAIN* (not start) |
| 849 | Maximize Distance to Closest Person | Python,Java | O(n) | O(1) | Medium | basic, 2 pointers, LC 855, google | AGAIN********* (2) |
| 860 | Lemonade Change | Python | O(n) | O(1) | Easy | amazon | OK* (2) |
| 0868 | Transpose Matrix | Python | O(r * c) | O(1) | Easy | basic | OK* |
| 885 | Spiral Matrix III | Python | O(max(m, n)^2) | O(1) | Medium | basic | AGAIN* (not start) |
| 888 | Fair Candy Swap | Python | O(m + n) | O(m + n) | Easy | basic,trick | OK* |
| 896 | Monotonic Array | Python | O(n) | O(1) | Easy | all,array ,fb | OK |
| 905 | Sort Array By Parity | Python | O(n) | O(1) | Easy | sort by lambda | OK |
| 909 | Snakes and Ladders | Python | O(n^2) | O(n^2) | Medium | array, matrix, dfs,complex,amazon | AGAIN***** (3) |
| 915 | Partition Array into Disjoint Intervals | Python | O(n) | O(n) | Medium | basic,trick | AGAIN* (not start) |
| 918 | Maximum Sum Circular Subarray | Python,Java | O(n) | O(1) | Medium | check# 053 Maximum Subarray,basic,trick | AGAIN** (2) |
| 921 | Minimum Add to Make Parentheses Valid | Python,Java | O(n) | O(1) | Medium | basic,trick | AGAIN** |
| 922 | Sort Array By Parity II | Python | O(n) | O(1) | Easy | basic | AGAIN* |
| 923 | 3Sum With Multiplicity | Python | O(n^2) | O(n) | Medium | AGAIN (not start) | |
| 932 | Beautiful Array | Python,Java | O(n) | O(n) | Medium | basic,trick, google | AGAIN** (not start) (1) |
| 941 | Valid Mountain Array | Python | O(n) | O(1) | Easy | basic,good basic | AGAIN* |
| 945 | Minimum Increment to Make Array Unique | Python | O(nlogn) | O(n) | Medium | trick,good | AGAIN** |
| 947 | Most Stones Removed with Same Row or Column | Python,Java | O(n) | O(n) | Medium | Union Find , dfs, trick,google | AGAIN** (1) (not start) |
| 949 | Largest Time for Given Digits | Python | O(1) | O(1) | Easy | OK* | |
| 950 | Reveal Cards In Increasing Order | Python,Java | O(n) | O(n) | Medium | queue, 2 pointers, google | AGAIN (not start) (2) |
| 954 | Array of Doubled Pairs | Python | O(n + klogk) | O(k) | Medium | counter,dict,trick | AGAIN** |
| 961 | N-Repeated Element in Size 2N Array | Python | O(n) | O(1) | Easy | OK | |
| 989 | Add to Array-Form of Integer | Python | O(n) | O(1) | Easy | add xxx to sum, fb | AGAIN (not start) |
| 004 | Median of Two Sorted Arrays | Python,Java | O(n) | O(1) | Hard | array, heapq, binary search, amazon | AGAIN* (1) |
| 10 | Regular Expression Matching | Python,Java | O(n) | O(1) | Hard | recursion, dp,fb | AGAIN (not start) |
| 056 | Merge Intervals | Python,Java | O(n) | O(1) | Medium | Curated Top 75,good trick,057 Insert Interval,twitter,M$,UBER,google,amazon,fb | OK********* (6) (but AGAIN) |
| 759 | Employee Free Time | Python | O(n) | O(1) | Hard | LC 56 and LC 986, heap, merger intervals, scanning line,amazon, fb, google, uber, airbnb | AGAIN********** (2) (not start) |
| 1007 | Minimum Domino Rotations For Equal Row | Java | O(n) | O(1) | Medium | google, array, dp | AGAIN (1) |
| 1014 | Best Sightseeing Pair | Python | Medium | dp, array, good basic, Spotify | AGAIN (not start) | ||
| 1027 | Longest Arithmetic Subsequence | Python,Java | Medium | dp, hash table, trick, google, amazon | AGAIN*** (not start) | ||
| 1031 | Maximum Sum of Two Non-Overlapping Subarrays | Java | Medium | prefix sum, slide window,google | AGAIN** (1) | ||
| 1041 | Robot Bounded In Circle | Python | Medium | array, math,amazon | AGAIN** (2) | ||
| 1094 | Car Pooling | Java | Medium | range addition, presum, LC 370 | AGAIN****** (3) (MUST) | ||
| 1109 | Corporate Flight Bookings | Python,Java | Medium | LC 370, difference array, good basic,amazon, google | AGAIN********* (MUST) (3) | ||
| 1248 | Count Number of Nice Subarrays | Python | Medium | LC 828, hash map, Prefix sum, dict, windown, good basic, deque, array,amazon | AGAIN************** (3) (MUST) | ||
| 1275 | Find Winner on a Tic Tac Toe Game | Python | Easy | amazon | AGAIN (not start) | ||
| 1564 | Put Boxes Into the Warehouse I | Java | Medium | google | AGAIN (not start) | ||
| 1567 | Maximum Length of Subarray With Positive Product | Python | Medium | good trick, array, dp, 2 pointers, amazon | AGAIN**** (1) (not start) | ||
| 1914 | Cyclically Rotating a Grid | Python | Medium | array, brute force, dequeueamazon | AGAIN (not start) | ||
| 3195 | Find the Minimum Area to Cover All Ones I | Java | Medium | array, LC weekly | AGAIN (1) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 2357 | Make Array Zero by Subtracting Equal Amounts | Java | O(n^2) | O(1) | Medium | set | Again (1) |
| 1316 | Distinct Echo Substrings | Java | O(n^2) | O(1) | Hard | set | Again (not start) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 1004 | Max Consecutive Ones III | Java | O(n^2) | O(1) | Medium | slide window | Again (1) |
| 1838 | Frequency of the Most Frequent Element | Java | O(n^2) | O(1) | Medium | slide window, binary search | AGAIN******** (1)(good) |
| # | Title | Solution | Time | Space | Difficulty | Status | Note |
|---|---|---|---|---|---|---|---|
| 001 | Two Sum | Python,Java,Scala | O(n) | O(n) | Easy | good basic,hash table,apple,amazon,UBER,grab,fb | OK*** (6) (but again) |
| 003 | Longest Substring Without Repeating Characters | Python,Java | O(n) | O(1) | Medium | Curated Top 75, 2 pointers, optimized (SLIDING WINDOW + DICT),good trick,hashMap, MUST,apple,amazon,fb | AGAIN**************** (12) (but AGAIN) |
| 036 | Valid Sudoku | Python,Java | O(9^2) | O(9) | Medium | array, hashset,UBER,apple,amazon | OK**** (3) (again) |
| 049 | Group Anagrams | Python,Scala,Java | O(n * glogg) | O(n) | Medium | Curated Top 75,good basic, dict,trick,dict + sort,UBER,amazon,fb | OK ********** (6) |
| 170 | Two Sum III - Data structure design | Python | O(n) | O(n) | Easy | 🔒,trick,good basic,linkedin,fb | OK*** (4) |
| 187 | Repeated DNA Sequences | Python,Java | O(n) | O(n) | Medium | basic,trick,set,linkedin, google | AGAIN** |
| 202 | Happy Number | Python,Java | O(k) | O(k) | Easy | twitter,airbnb,UBER | AGAIN** (4) |
| 204 | Count Primes | Python | O(n) | O(n) | Medium | good trick, cache, dict, set,M$,amazon | AGAIN******** (5) |
| 205 | Isomorphic Strings | Python,Java | O(n) | O(1) | Easy | basic,trick,bloomberg | AGAIN** |
| 217 | Contains Duplicate | Python,Java | O(n) | O(n) | Easy | Curated Top 75,yahoo,airbnb | OK |
| 219 | Contains Duplicate II | Python,Java | O(n) | O(n) | Easy | basic,trick,hash table | AGAIN* |
| 244 | Shortest Word Distance II | Python | ctor:O(n), lookup:O(a + b) | O(n) | Medium | 🔒 | AGAIN (not start*) |
| 246 | Strobogrammatic Number | Python,Java | O(n) | O(1) | Easy | 🔒,google,fb | OK* (5) |
| 249 | Group Shifted Strings | Python,Java | O(nlogn) | O(n) | Medium | LC 49, 🔒, hashmap, char,apple,UBER,google | OK *****(6) (but again) |
| 266 | Palindrome Permutation | Python | O(n) | O(1) | Easy | 🔒 | OK |
| 288 | Unique Word Abbreviation | Python | ctor:O(n), lookup:O(1) | O(k) | Medium | AGAIN (2)(not start) | |
| 290 | Word Pattern | Python | O(n) | O(c) | Easy | basic, chcek# 205 Isomorphic Strings,good basic,for ptn, word in zip(pattern, words),dropbox ,UBER | AGAIN* (3) |
| 299 | Bulls and Cows | Python | O(n) | O(1) | Easy | trick,map(operator.eq, a, b),amazon,airbnb,google | AGAIN* (3) |
| 314 | Binary Tree Vertical Order Traversal | Python | O(n) | O(n) | Medium | 🔒,BFS,DFS,hash table,tree,trick,google,amazon,fb, m$ | OK**** (6) |
| 325 | Maximum Size Subarray Sum Equals k | Python,Java | O(n) | O(n) | Medium | prefix sum, 🔒,hashmap,good trick,dict,fb | AGAIN***************** (8) (MUST) |
| 356 | Line Reflection | Python,Java | O(n) | O(n) | Medium | 🔒, Hash, Two Pointers,math,google | AGAIN (not start) |
| 359 | Logger Rate Limiter | Python,Java | O(1), amortized | O(k) | Easy | OK | |
| 387 | First Unique Character in a String | Python | O(n) | O(n) | Easy | amazon,apple,fb | OK |
| 388 | Longest Absolute File Path | Python | O(n) | O(d) | Medium | stack, hash table, good trick, file system,google | AGAIN******* (3) |
| 409 | Longest Palindrome | Python | O(n) | O(1) | Easy | OK* | |
| 424 | Longest Repeating Character Replacement | Python,Java | O(n) | O(1) | Medium | Curated Top 75, hash map,silding window,two pointers,good trick, LC blind pattern | AGAIN************* (9) (MUST) |
| 438 | Find All Anagrams in a String | Python,Java | O(n) | O(1) | Medium | trick,AGAIN,sliding window,acc Counter,amazon,fb, apple, google, uber, yahoo | AGAIN************** (11)(must) |
| 447 | Number of Boomerangs | Python | O(n^2) | O(n) | Easy | trick,google | AGAIN (3) (not start) |
| 454 | 4Sum II | Python | O(n^2) | O(n^2) | Medium | check LC 018 4SUM,trick,basic,amazon | AGAIN** |
| 463 | Island Perimeter | Python,Java | O(n) | O(k) | Medium | basic,hash table,google,fb, amazon | AGAIN** (2) |
| 470 | Implement Rand10() Using Rand7() | Python | O(1) | O(1) | Medium | trick,google | AGAIN** (3) |
| 473 | Matchsticks to Square | Python,Java | O(n * s * 2^n) | O(n * (2^n + s)) | Medium | good trick, backtrack | AGAIN****** (2) |
| 523 | Continuous Subarray Sum | Python,Java | O(n) | O(k) | Medium | sub array sum, check# 560 Subarray Sum Equals K,good trick,substring,hash table,AGAIN,M$,fb,apple | AGAIN*************** (10) (MUST) |
| 525 | Contiguous Array | Python,Java | O(n) | O(n) | Medium | sub-array sum,good basic,array,hashmap,cache,AGAIN,fb, amazon | AGAIN*************** (11) (MUST) |
| 532 | K-diff Pairs in an Array | Python | O(n) | O(n) | Medium | hash table,basic,collections.Counter(),a-b =k -> a = k + b,amazon | AGAIN********** (6) |
| 554 | Brick Wall | Python,Java | O(n) | O(m) | Medium | trick,hash map,bloomberg,fb, grab | AGAIN******** (6) |
| 560 | Subarray Sum Equals K | Python,Java | O(n) | O(n) | Medium | prefix sum,must check,check# 523 Continuous Subarray Sum, LC 1268,basic,substring,good trick,google,fb | AGAIN************** (7) (MUST) |
| 561 | Array Partition I | Python | O(r) | O(r) | Easy | OK | |
| 575 | Distribute Candies | Python | O(n) | O(n) | Easy | OK | |
| 594 | Longest Harmonious Subsequence | Python | O(n) | O(n) | Easy | basic,good trick | OK* (3) |
| 599 | Minimum Index Sum of Two Lists | Python | O((m + n) * l) | O(m * l) | Easy | yelp | OK* |
| 609 | Find Duplicate File in System | Python | O(n * l) | O(n * l) | Medium | collections.defaultdict(list),dropbox | OK* |
| 657 | Robot Return to Origin | Python | Easy | amazon | OK (2) | ||
| 748 | Shortest Completing Word | Python | O(n) | O(1) | Easy | collections.Counter,hash table,google | AGAIN* (3) |
| 760 | Find Anagram Mappings | Python | O(n) | O(n) | Easy | basic,collections.defaultdict | OK |
| 771 | Jewels and Stones | Python | O(m + n) | O(n) | Easy | amazon | OK (2) |
| 811 | Subdomain Visit Count | Python | O(n) | O(n) | Easy | indeed,bloomberg | AGAIN (not start) |
| 822 | Card Flipping Game | Python | O(n) | O(n) | Medium | good basic | AGAIN* (3) |
| 825 | Friends Of Appropriate Ages | Python | O(a^2 + n) | O(a) | Medium | good basic,counter,AGAIN,fb | AGAIN***** (5) |
| 869 | Reordered Power of 2 | Python | O(1) | O(1) | Medium | trick,basic,bit manipulation,bit | AGAIN* |
| 873 | Length of Longest Fibonacci Subsequence | Python | O(n^2) | O(n) | Medium | trick,DP,Fibonacci,set | AGAIN** |
| 957 | Prison Cells After N Days | Python | O(1) | O(1) | Medium | trick,DP,mod | AGAIN (not start) |
| 966 | Vowel Spellchecker | Python | O(n) | O(w) | Medium | trick,dict,set | AGAIN (not start) |
| 974 | Subarray Sums Divisible by K | Python | O(n) | O(k) | Medium | variant of# 560 Subarray Sum Equals K ,trick,basic | AGAIN** (3) (not start) |
| 992 | Subarrays with K Different Integers | Python | O(n) | O(k) | Hard | 2 pointers, hashmap, sliding window, amazon | AGAIN (not start) |
| 1010 | Pairs of Songs With Total Durations Divisible by 60 | Python | Medium | good basicm dict, array,amazon | AGAIN********* (4) (MUST) | ||
| 1099 | Two Sum Less Than K | Python | Medium | dict, sort,amazon | AGAIN* (1) (not start) | ||
| 1121 | Divide Array Into Increasing Sequences | Java | Hard | dict, google | Again (not start) | ||
| 1131 | Rank Transform of an Array | Python | Easy | dict, array,amazon | OK* (1) | ||
| 1170 | Compare Strings by Frequency of the Smallest Character | Java | Medium | hashmap, binary search,google | AGAIN*** (1)s | ||
| 1257 | Smallest Common Region | Java | Medium | hashmap, good trick, lowest common ancestor (LCA) | AGAIN (not start) | ||
| 1296 | Divide Array in Sets of K Consecutive Numbers | Python | Medium | LC 846, dict,google | AGAIN (not start) | ||
| 1923 | Longest Common Subpath | Python | O(n) | O(h) | Hard | hash, bit,amazon | AGAIN (not start) |
| 2506 | Count Pairs Of Similar Strings | Java | O(n) | O(h) | Easy | hashmap, LC weekly | AGAIN (1) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 002 | Add Two Numbers | Python,Java | O(n) | O(1) | Medium | Curated Top 75, check# 445 Add Two Numbers II,basic,linked list,airbnb,amazon,fb | OK**** (6) (but again) |
| 021 | Merge Two Sorted Lists | Python,Java | O(n) | O(1) | Easy | Curated Top 75,UBER,amazon,apple,fb | OK******** (6) (but again) |
| 023 | Merge k sorted lists | Python,Java | O(n) | O(h) | Hard | Curated Top 75, linked list, check#21 Merge Two Sorted Lists,amazon | OK**** (2) (but again !!! |
| 024 | Swap Nodes in Pairs | Python,Java | O(n) | O(1) | Medium | GOOD basic, LC 100 like,UBER,amazon,fb | AGAIN**************** (8) (MUST) |
| 025 | Reverse Nodes in k-Group | Python,Java | O(n) | O(1) | Hard | good trick, reverse linkedlist, reverse K linkedlist, amazon, google, fb, m$ | AGAIN********** (4) |
| 061 | Rotate List | Python,Java | O(n) | O(1) | Medium | basic | AGAIN (2) |
| 082 | Remove Duplicates from Sorted List II | Python,Java | O(n) | O(1) | Medium | good basic,check# 083 Remove Duplicates from Sorted List | AGAIN (3) ***** |
| 083 | Remove Duplicates from Sorted List | Python,Java | O(n) | O(1) | Easy | basic | OK* |
| 92 | Reverse Linked List II | Python,Java | O(n) | O(1) | Medium | # 206 Reverse Linked List,good trick, fb, apple, google, amazon, m$ | AGAIN*************** (9) (MUST) |
| 138 | Copy List with Random Pointer | Python,Java | O(n) | O(1) | Medium | trick, recursive, linked list,hash table,UBER,M$,amazon,fb | AGAIN******* (7) |
| 160 | Intersection of Two Linked Lists | Python,Java | O(m + n) | O(1) | Easy | basic, hash table, 2 pointers, linkedlist,airbnb,amazon,fb | OK******* (7) (again!) |
| 203 | Remove Linked List Elements | Python ,Java | O(n) | O(1) | Easy | linked list basic,amazon | OK** (3) |
| 206 | Reverse Linked List | Python,Java | O(n) | O(1) | Easy | Curated Top 75,good basic,amazon,fb | OK*********** (9) (MUST again) |
| 234 | Palindrome Linked List | Python,Java | O(n) | O(1) | Easy | linked list,amazon,fb | OK (4) |
| 237 | Delete Node in a Linked List | Python,Java | O(1) | O(1) | Easy | LintCode, apple | OK * (1) (but again) |
| 328 | Odd Even Linked List | Python | O(n) | O(1) | Medium | basic | OK** (2) |
| 369 | Plus One Linked List | Python,Java | O(n) | O(1) | Medium | 🔒, linkedlist,basic, google | AGAIN****** (3) |
| 445 | Add Two Numbers II | Python | O(m + n) | O(m + n) | Medium | trick, linked list, string,good basic,amazon | AGAIN*** (3) |
| 725 | Split Linked List in Parts | Python | O(n + k) | O(1) | Medium | mod, split linked list, linked list, good trick,amazon | AGAIN************ (6) (again) |
| 817 | Linked List Components | Python,Java | O(m + n) | O(m) | Medium | set, array, linkedlist, google | AGAIN** (1) |
| 430 | Flatten a Multilevel Doubly Linked List | Python,Java | Medium | good trick,doubly linked list,dfs,iterative, stack,fb, google | AGAIN******** (6) | ||
| 707 | Design Linked List | Python,Java | O(n) | O(h) | Medium | linked list basic OP | AGAIN (1) |
| 708 | Insert into a Cyclic Sorted List | Python,Java | O(n) | O(h) | Medium | AGAIN,cyclic linked list,good trick,google,amazon,fb , google | AGAIN******** (4) |
| 1836 | Remove Duplicates From an Unsorted Linked List | Java | O(n) | O(h) | Medium | linked list | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 020 | Valid Parentheses | Python,Java | O(n) | O(n) | Easy | Curated Top 75,good basic,fb,amazon | OK** (6) |
| 032 | Longest Valid Parentheses | Python | O(n) | O(n) | Hard | brute force, dp, stackm deque, LC top 100 likes,amazon, fb, m$ | AGAIN***** (1) (not start) |
| 071 | Simplify Path | Python,Java | O(n) | O(n) | Medium | basic,stack,amazon,fb | OK** (5) |
| 085 | Maximal Rectangle | Python | O(n) | O(n) | Hard | top-100-like, brute force, stack, dp, LC 084, google, amazon, apple | AGAIN (not start) |
| 101 | Symmetric Tree | Python,Java | O(n) | O(h) | Easy | good basic,bfs,dfs,linkedin,M$,amazon,fb, google | AGAIN********** (6) |
| 150 | Evaluate Reverse Polish Notation | Python,Java | O(n) | O(n) | Medium | stack, good trick,amazon | AGAIN********* (5) |
| 155 | Min Stack | Python,Java | O(n) | O(1) | Medium | basic, stack, data structure,amazon | OK*********** (5) |
| 173 | Binary Search Tree Iterator | Python,Java | O(1) | O(h) | Medium | good basic, stack,tree, stack, M$,linkedin,google,amazon,fb, google | OK***** (5) |
| 224 | Basic Calculator | Python | O(n) | O(n) | Hard | basic,trick,stack, LC 227, amazon | AGAIN******* (3) |
| 227 | Basic Calculator II | Python | O(n) | O(n) | Medium | delay op, LC 224,good trick,stack,airbnb ,fb, amazon | AGAIN************** (6) (MUST) |
| 232 | Implement Queue using Stacks | Python,Java | O(1), amortized | O(n) | Easy | stack, stack-queue, EPI, LintCode,amazon | AGAIN*** (3)(MUST) |
| 255 | Verify Preorder Sequence in Binary Search Tree | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 321 | Create Maximum Number | Java | O(n) | O(1) | Hard | dp, greedy, mono-stack, google | AGAIN (not start) (2) |
| 331 | Verify Preorder Serialization of a Binary Tree | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 341 | Flatten Nested List Iterator | Python | O(n) | O(h) | Medium | LC 284, 🔒 Iterator, stack, generator,good basic,amazon,fb*** | AGAIN********* (6) |
| 385 | Mini Parser | Python | O(n) | O(h) | Medium | AGAIN | |
| 394 | Decode String | Python,Java | O(n) | O(h) | Medium | stack, good basic!!!!, pre num string, LC 224, LC 227,amazon,google | AGAIN************** (8) (MUST) |
| 439 | Ternary Expression Parser | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 456 | 132 Pattern | Python | O(n) | O(n) | Medium | AGAIN (not start) | |
| 496 | Next Greater Element I | Python,Java | O(n) | O(n) | Easy | good basic, stack,monotonic stack, LC 739, LC 503, LC 406 | OK************ (6) (but again) |
| 503 | Next Greater Element II | Python,Java | O(n) | O(n) | Medium | good basic, stack, LC 739, LC 503, LC 406, next_big_val_idx | AGAIN************* (7) |
| 636 | Exclusive Time of Functions | Python | O(n) | O(n) | Medium | trick,AGAIN,stack,UBER,fb | AGAIN********** (4) |
| 682 | Baseball Game | Python,Java | O(n) | O(n) | Easy | good basic, stack,amazon | OK* (3) |
| 735 | Asteroid Collision | Python | O(n) | O(n) | Medium | good basic, stack, m$, GS, fb,amazon | AGAIN************** (5) |
| 739 | Daily Temperatures | Python,Java | O(n) | O(n) | Medium | LC 739, LC 503, LC 406, LC 496, LC 42, Monotonic stack, good trick,amazon | AGAIN******************* (12) (MUST) |
| 772 | Basic Calculator III | Java | O(n) | O(n) | Medium | check LC 224, 227, stack | AGAIN (not start) |
| 853 | Car Fleet | Python,Java | O(nlogn) | O(n) | Medium | stack, good basic, google, amz | AGAIN********* (5) |
| 856 | Score of Parentheses | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 872 | Leaf-Similar Trees | Python,Java | O(n) | O(h) | Easy | AGAIN* | |
| 895 | Maximum Frequency Stack | Python,Java | O(n) | O(h) | Hard | good basic, heap, design, stack, amazon, apple, linkedin, m$, twitter | AGAIN********** (1) (not start) |
| 901 | Online Stock Span | Python,Java | O(n) | O(n) Medium | AGAIN (not start) | ||
| 946 | Validate Stack Sequences | Python | O(n) | O(n) | Medium | AGAIN | |
| 1047 | Remove All Adjacent Duplicates in String | Python,Java | O(n) | O(n) | easy | good basic, fb, amazon, google | AGAIN************ (3) (MUST) |
| 1209 | Remove All Adjacent Duplicates in String II | Python | O(n) | O(n) | Medium | good basic, stack, two pointers, greedy, fb, amamzon, apple, spotify | AGAIN************ (3) (MUST) |
| 1703 | Minimum Adjacent Swaps for K Consecutive Ones | Python | O(n) | O(n) | Hard | heap, sliding window, amazon | AGAIN (not start) |
| 1896 | Minimum Cost to Change the Final Value of Expression | Python | O(n) | O(n) | Hard | complex, stack, dp, dp+stack, dfs,amazon | AGAIN (not start) |
| 2104 | Sum of Subarray Ranges | Python,Java | O(n) | O(1) | Medium | LC 907, monotonic stack, brute force, 2 pointers, dp,amazon | AGAIN******* (4) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 94 | Binary Tree Inorder Traversal | Python | O(n) | O(1) | Medium | tree, iteration, recursion,good basic,Morris Traversal,M$,fb | AGAIN********* (4) (MUST) |
| 124 | Binary Tree Maximum Path Sum | Python,Java | O(n) | O(1) | Hard | Curated Top 75, google, amazon, fb, m$, twitter | AGAIN*********** (6) (MUST) |
| 144 | Binary Tree Preorder Traversal | Python,Java | O(n) | O(1) | Medium | Morris Traversal | OK |
| 145 | Binary Tree Postorder Traversal | Java | O(n) | O(1) | Medium | Morris Traversal | OK |
| 208 | Implement Trie (Prefix Tree) | Python,Java | O(n) | O(1) | Medium | Curated Top 75, dict tree, LC 211, trie,amazon,fb | AGAIN************** (7) (MUST) |
| 211 | Design Add and Search Words Data Structure | Python,Java | O(min(n, h)) | O(min(n, h)) | Medium | Curated Top 75,Trie, recursive, node, hashMap, do# 208 first,amazon ,fb | AGAIN*********** (8) (MUST) |
| 226 | Invert Binary Tree | Python,Java | O(n) | O(h),O(w) | Easy | Curated Top 75, good basic | OK******* (4) (but again) |
| 250 | Count Univalue Subtrees | Python,Java | O(n) | O(h),O(w) | Medium | LC 572 | not start |
| 297 | Serialize and Deserialize Binary Tree | Python,Java | O(n) | O(h),O(w) | Hard | Curated Top 75, BFS, DFS, Binary Tree | again******* (4) |
| 307 | Range Sum Query - Mutable | Python,Java | ctor:O(n), update:O(logn), query:O(logn) | O(n) | Medium | LintCode, DFS, Segment Tree, BIT, check#303 Range Sum Query - Immutable , google | AGAIN* (2)(not start) |
| 427 | Construct Quad Tree | Java | O(n) | O(h),O(w) | Medium | tree, Quadtrees | again (not start) |
| 536 | Construct Binary Tree from String | Python,Java | O(n) | O(h) | Medium | 🔒, tree, recursive,trick, check# 606 Construct String from Binary Tree,amazon | AGAIN******** (5) |
| 538 | Convert BST to Greater Tree | Python,Java | O(n) | O(h) | Medium | good basic, dfs, bfs, tree,amazon | OK********* (6) (but again!) |
| 543 | Diameter of Binary Tree | Python,Java | O(n) | O(h) | Easy | dfs, tree,trick,google,amazon,fb | AGAIN*********** (7)(MUST) |
| 545 | Boundary of Binary Tree | Python | O(n) | O(h) | Medium | recursive, dfs, tree boundary, tree,🔒,good trick,amazon | AGAIN********* (6) |
| 548 | Split Array with Equal Sum | Python | O(n^2) | O(n) | Medium | 🔒,good trick,array | AGAIN*** (2) |
| 563 | Binary Tree Tilt | Python | O(n) | O(n) | Easy | AGAIN | |
| 572 | Subtree of Another Tree | Python,Java | O(m * n) | O(h) | Easy | Curated Top 75, LC 100, recursive call recursion func, good basic, dfs, bfs,amazon,fb | OK************* (10) (but again) |
| 606 | Construct String from Binary Tree | Python | O(n) | O(h) | Easy | good basic, tree, dfs, LC # 536,amazon | OK******** (7) (again!) |
| 617 | Merge Two Binary Trees | Python,Java | O(n) | O(h) | Easy | tree, dfs, bfs,good basic,amazon | OK************* (7) (but again) |
| 623 | Add One Row to Tree | Python | O(n) | O(h) | Medium | good basic,dfs,bfs | AGAIN** (2) |
| 637 | Average of Levels in Binary Tree | Python,Java | O(n) | O(h) | Easy | bfs,dfs,good basic,fb | OK*** (4) |
| 652 | Find Duplicate Subtrees | Python,Java | O(n) | O(n) | Medium | AGAIN, good basic,path, dfs, Hashmap,amazon | AGAIN************** (7) |
| 653 | Two Sum IV - Input is a BST | Python,Java | O(n) | O(h) | Easy | Two Pointers,2 sum,bfs,dfs,amazon,fb | OK******* (4) |
| 654 | Maximum Binary Tree | Python,Java | O(n) | O(n) | Medium | LintCode, Descending Stack,good basic | AGAIN* (2) |
| 655 | Print Binary Tree | Python | O(n) | O(h) | Medium | AGAIN* (2) (not start) | |
| 662 | Maximum Width of Binary Tree | Python | O(n) | O(h) | Medium | width of tree, bfs, dfs,trick,amazon | AGAIN********* (5) |
| 663 | Equal Tree Partition | Python | O(n) | O(n) | Medium | # LC 508, AGAIN, 🔒 , Hash, tree, dfs ,trick,good trick,amazon | OK******** (8) |
| 677 | Map Sum Pairs | Python | O(n) | O(t) | Medium | Trie,trick,hard | AGAIN* (2) (not start) |
| 684 | Redundant Connection | Python,Java | O(n) | O(n) | Medium | dfs, graph, Union Find,basic | AGAIN****** (3) (not start) |
| 687 | Longest Univalue Path | Python,Java | O(n) | O(h) | Medium | basic, dfs, tree,trick,google | AGAIN**** (4) |
| 814 | Binary Tree Pruning | Python | O(n) | O(h) | Medium | DFS,basic | AGAIN* (2) |
| 863 | All Nodes Distance K in Binary Tree | Python,Java | O(n) | O(n) | Medium | LC 752, tree-> graph, move upward, tree, DFS + BFS,trick,hard,amazon | AGAIN************ (4)(MUST) |
| 866 | Smallest Subtree with all the Deepest Nodes | Python | O(n) | O(h) | Medium | DFS,trick,basic | AGAIN** (2) |
| 889 | Construct Binary Tree from Preorder and Postorder Traversal | Python,Java | O(n) | O(h) | Medium | DFS,stack,trick, tree, recursive, google | AGAIN** (2) (not start*) |
| 897 | Increasing Order Search Tree | Python | O(n) | O(h) | Easy | DFS,good basic,inorder | AGAIN** (2) |
| 919 | Complete Binary Tree Inserter | Python | ctor:O(n) insert:O(1) get_root:O(1) | O(n) | Medium | bst | AGAIN** (2) |
| 938 | Range Sum of BST | Python | O(n) | O(h) | Medium | DFS, check# 108 Convert Sorted Array to Binary Search Tree | AGAIN* (2) |
| 951 | Flip Equivalent Binary Trees | Python,Java | O(n) | O(h) | Medium | recursion, tree, DFS, google | AGAIN***s (3) |
| 958 | Check Completeness of a Binary Tree | Python | O(n) | O(w) | Medium | BFS,DFS,basic | AGAIN** (2) |
| 965 | Univalued Binary Tree | Python | O(n) | O(h) | Easy | DFS,BFS,good basic | AGAIN** (2) |
| 971 | Flip Binary Tree To Match Preorder Traversal | Python | O(n) | O(h) | Medium | DFS,trick | AGAIN** (2) (not start) |
| 979 | Distribute Coins in Binary Tree | Python | O(n) | O(h) | Medium | DFS,trick | AGAIN*** (2) |
| 508 | Most Frequent Subtree Sum | Python | Medium | tree, dfs, bfs, good basic,amazon | OK*********** (4) (but again MUST) | ||
| 683 | K Empty Slots | Python | Hard | BST, tree, bucket,google | not start | ||
| 701 | Insert into a Binary Search Tree | Python,Java | Medium | good basic, BST, tree, BFS, DFS | OK***** (3) | ||
| 1032 | Stream of Characters | Java | Hard | trie, google | AGAIN (not start) | ||
| 1157 | Online Majority Element In Subarray | Java | Hard | tree, google | AGAIN (not start) | ||
| 1325 | Delete Leaves With a Given Value | Java | Medium | dfs, tree, good basic, LC 450 | AGAIN*** (2) | ||
| 1339 | Maximum Product of Splitted Binary Tree | Python | Medium | dfs, tree, amazon | AGAIN*** (1) (not start) | ||
| 1372 | Longest ZigZag Path in a Binary Tree | Python | Medium | dfs, bfs, post order, good trick, tree, amazon | AGAIN*** (1) (not start) | ||
| 1448 | Count Good Nodes in Binary Tree | Python,Java | Medium | max in path, dfs, bfs, good trick, tree, needcode, google, amz, m$ | AGAIN************* (3) (MUST) | ||
| 1522 | Diameter of N-Ary Tree | Java | Medium | LC 543, tree | AGAIN (not start) | ||
| 1666 | Change the Root of a Binary Tree | Java | Medium | LC 1448, good trick, google | AGAIN (1) (not start) | ||
| 1740 | Find Distance in a Binary Tree | Java | Medium | LCA + NODE DIST + DFS, DFS, LCA | AGAIN (1)**** | ||
| 2415 | Reverse Odd Levels of Binary Tree | Java | Medium | LC 226, dfs, bfs, tree | AGAIN (not start) | ||
| 2509 | Cycle Length Queries in a Tree | Java | Hard | LC weekly, tree | AGAIN (not start) | ||
| 2707 | Extra Characters in a String | Java | Medium | dp, Trie | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 264 | Ugly Number II | Python | O(n) | O(1) | Medium | good trick, LC 263, LC 313, Heap, LintCode , DP, M$ | AGAIN*********** (4) (MUST) |
| 313 | Super Ugly Number | Python | O(n * k) | O(n + k) | Medium | BST, Heap | AGAIN (not start*) |
| 373 | Find K Pairs with Smallest Sums | Python,Java | O(k * log(min(n, m, k))) | O(min(n, m, k)) | Medium | google, heap | AGAIN (not start) |
| 378 | Kth Smallest Element in a Sorted Matrix | Python | O(k * log(min(n, m, k))) | O(min(n, m, k)) | Medium | LintCode | AGAIN (not start) |
| 502 | IPO | Java | O(k * log(min(n, m, k))) | O(min(n, m, k)) | Hard | PQ | AGAIN (not start) |
| 846 | Hand of Straights | Python,Java | O(nlogn) | O(n) | Medium | LC 1296, good basic, PQ, Treemap, hashmap, google | OK******** (3) |
| 855 | Exam Room | Python,Java | seat:O(logn) leave:O(logn) | O(n) | Medium | treeSet, BST, Hash,trick, LC 849, google | AGAIN* (3) (not start) |
| 295 | Find Median from Data Stream | Python,Java | Hard | Curated Top 75, priority queue, trick ,heap, stream,amazon | AGAIN****** (6) | ||
| 703 | Kth Largest Element in a Stream | Python,Java | Easy | heap, priority queue,amazon | AGAIN******** (5) | ||
| 1046 | Last Stone Weight | Python,Java | Easy | Heap, Priority Queue | OK | ||
| 1130 | Minimum Cost Tree From Leaf Values | Python | Medium | LC 1167,heap | not start | ||
| 1167 | Minimum Cost to Connect Sticks | Python | Medium | LC 1130, good basic,heap,amazon | AGAIN***** (3) | ||
| 1353 | Maximum Number of Events That Can Be Attended | Python,Java | Medium | LC 252, 253, good trick, meeting room, heap, PRIORITY QUEUE, fb, twitter,amazon | AGAIN********* (3) MUST | ||
| 1405 | Longest Happy String | Java | Medium | PQ | AGAIN (not start) | ||
| 1481 | Least Number of Unique Integers after K Removals | Python | Medium | good trick, greedy, Counter, dict, heap,amazon | AGAIN******** (3) | ||
| 1834 | Single-Threaded CPU | Java | Medium | good trick, heap, pq | AGAIN***** (1) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 136 | Single Number | Python | O(n) | O(1) | Easy | airbnb,amazon,fb | OK |
| 137 | Single Number II | Python | O(n) | O(1) | Medium | OK | |
| 190 | Reverse Bits | Python,Java | O(1) | O(1) | Easy | Curated Top 75, bit,apple | AGAIN*** (2) |
| 191 | Number of 1 Bits | Python,Java | O(1) | O(1) | Easy | Curated Top 75, apple | OK* |
| 201 | Bitwise AND of Numbers Range | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 231 | Power of Two | Python | O(1) | O(1) | Easy | good basic, Bit Manipulation ,amazon | OK*** (3) |
| 260 | Single Number III | Python | O(n) | O(1) | Medium | xor,^=,^ | AGAIN* |
| 268 | Missing Number | Python,Java | O(n) | O(1) | Medium | Curated Top 75,xor,amazon,fb | OK* (2) |
| 318 | Maximum Product of Word Lengths | Python | O(n) ~O(n^2) | O(n) | Medium | Bit Manipulation, Counting Sort, Pruning | AGAIN (not start) |
| 342 | Power of Four | Python | O(1) | O(1) | Easy | power of num | OK* |
| 371 | Sum of Two Integers | Python,Java | O(1) | O(1) | Medium | Curated Top 75,good basic,fb | AGAIN********* (5) (bit op not start) |
| 389 | Find the Difference | Python | O(n) | O(1) | Easy | amazon | OK (2) |
| 393 | UTF-8 Validation | Python | O(n) | O(1) | Medium | utf-8 encoding,google,fb | AGAIN**** (not start*) (5) |
| 401 | Binary Watch | Python | O(1) | O(1) | Easy | OK* | |
| 421 | Maximum XOR of Two Numbers in an Array | Python | O(n) | O(n) | Medium | AGAIN (not start) | |
| 461 | Hamming Distance | Python | O(1) | O(1) | Easy | fb | OK* (2) |
| 462 | Minimum Moves to Equal Array Elements II | Python | O(n) on average | O(1) | Medium | AGAIN* | |
| 477 | Total Hamming Distance | Python | O(n) | O(1) | Medium | bit manipulation,fb | AGAIN****** (not start*) (4) |
| 645 | Set Mismatch | Python | O(n) | O(1) | Easy | amazon | OK* (3) |
| 693 | Binary Number with Alternating Bits | Python | O(1) | O(1) | Easy | trick | AGAIN* |
| 762 | Prime Number of Set Bits in Binary Representation | Python | O(1) | O(1) | Easy | basic,Bit_Manipulation,prime number,amazon | OK* (4) |
| 868 | Binary Gap | Python | O(1) | O(1) | Easy | trick,linear scan | AGAIN* |
| 898 | Bitwise ORs of Subarrays | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 1573 | Number of Ways to Split a String | Python | O(n) | O(1) | Medium | amazon, binary | AGAIN** (not start) |
| 1915 | Number of Wonderful Substrings | Python | O(n) | O(1) | Medium | bit mask, bit, prefix sum, dp,amazon | AGAIN*** (2) (not start) |
| 3688 | Bitwise OR of Even Numbers in an Array | Java | O(n) | O(1) | Medium | bit mask | OK |
| # | Title | Solution | Time | Space | Difficulty | Status, Note | Status |
|---|---|---|---|---|---|---|---|
| 005 | Longest Palindromic Substring | Python,Java | O(n) | O(n) | Medium | Curated Top 75, LC 647, good trick, 2 pointer, recursive,Manacher's Algorithm, LC 100 like,DP,UBER,amazon,fb | AGAIN************** (8)(MUST) |
| 006 | ZigZag Conversion | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 008 | String to Integer (atoi) | Python | O(n) | O(1) | Medium | string op,regular expression,UBER,amazon,fb | AGAIN***** (5) |
| 014 | Longest Common Prefix | Python,Java | O(n * k) | O(1) | Easy | good basic, LCP, str, binary search, scan | AGAIN !!!! (4) |
| 028 | Implement strStr() | Python,Java | O(n + k) | O(k) | Easy | KMP Algorithm,fb | OK (3) |
| 038 | Count and Say | Python,Java | O(n * 2^n) | O(2^n) | Medium | recursion,iteration, basic,fb | AGAIN*********** (5) |
| 43 | Multiply Strings | Python,Java | O(m * n) | O(m + n) | Medium | twitter,fb | AGAIN*** (3) |
| 058 | Length of Last Word | Python | O(n) | O(1) | Easy | OK | |
| 067 | Add Binary | Python,Java | O(n) | O(1) | Easy | bit op,good basic,fb,amazon | OK***** (7) (but again) |
| 076 | Minimum Window Substring | Python,Java | Hard | slide window, good pattern,Curated Top 75 | AGAIN*********** (3) | ||
| 125 | Valid Palindrome | Python,Java | O(n) | O(1) | Easy | Curated Top 75, LC 680,amazon,fb | OK |
| 151 | Reverse Words in a String | Python | O(n) | O(1) | Medium | amazon,fb | OK (2) |
| 161 | One Edit Distance | Python | O(m + n) | O(1) | Medium | 🔒, trick, recursion, string, ,fb | AGAIN ******** (6)(AGAIN) |
| 165 | Compare Version Numbers | Python | O(n) | O(1) | Medium | good basic, string,amazon,apple | OK** (5) |
| 186 | Reverse Words in a String II | Python | O(n) | O(1) | Medium | LC 151, LC 557, 🔒,M$,UBER,amazon | AGAIN* (3) |
| 242 | Valid Anagram | Python,Java | O(n) | O(1) | Easy | Curated Top 75, LintCode,amazon,fb | OK |
| 271 | Encode and Decode Strings | Python,Java | O(n) | O(1) | Medium | Curated Top 75, decode-encode,string op, check# 394 Decode String ,🔒,google | AGAIN*** (3) |
| 306 | Addictive Number | Python | O(n^3) | O(n) | Medium | AGAIN (not start*) | |
| 340 | Longest Substring with At Most K Distinct Characters | Python,Java | O(n^3) | O(n) | Hard | string, sliding window,google | not start |
| 383 | Ransom Note | Python | O(n) | O(1) | Easy | EPI, apple | OK* |
| 405 | Convert a Number to Hexadecimal | Python | O(n) | O(1) | Easy | basicsdecimal -> Hexadecimal | AGAIN |
| 408 | Valid Word Abbreviation | Python | O(n) | O(1) | Easy | 🔒 | AGAIN (not start) |
| 415 | Add Strings | Python,Java | O(n) | O(1) | Easy | good basic,add xxx to sum,Airbnb,google,fb | OK****** (4) |
| 434 | Number of Segments in a String | Python | O(n) | O(1) | Easy | OK | |
| 443 | String Compression | Python | O(n) | O(1) | Easy | shoptify,basics | AGAIN** |
| 459 | Repeated Substring Pattern | Python | O(n) | O(n) | Easy | good basic, string,KMP Algorithm,amazon | OK*** (6) |
| 468 | Validate IP Address | Python | O(1) | O(1) | Medium | ip basic,string,twitter,fb,amazon | AGAIN****** (5) |
| 482 | License Key Formatting | Python,Java | O(n) | O(1) | Easy | string, basic,google | OK** (4) (again) |
| 520 | Detect Capital | Python | O(l) | O(1) | Easy | OK | |
| 521 | Longest Uncommon Subsequence I | Python | O(min(a, b)) | O(1) | Easy | OK* | |
| 522 | Longest Uncommon Subsequence II | Python | O(l * n^2) | O(1) | Medium | Sort | AGAIN (not start) |
| 524 | Longest Word in Dictionary through Deleting | Python,Java | O((d * l) * logd) | O(1) | Medium Sort, dict, brute force,google | AGAIN (not start) | |
| 539 | Minimum Time Difference | Python | O(nlogn) | O(n) | Medium | basic,map & zip trick | AGAIN** |
| 541 | Reverse String II | Python | O(n) | O(1) | Easy | AGAIN* | |
| 551 | Student Attendance Record I | Python | O(n) | O(1) | Easy | OK | |
| 556 | Next Greater Element III | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 557 | Reverse Words in a String III | Python | O(n) | O(1) | Easy | OK | |
| 616 | Add Bold Tag in String | Python | O(n * d * l) | O(n) | Medium | 🔒,google | AGAIN (not start) |
| 647 | Palindromic Substrings | Python,Java | O(n) | O(n) | Medium | Curated Top 75, LC 005, greedy, DP, expand from center, 2 pointers,good basic,Manacher's Algorithm,Linkedin,amazon,fb | OK********* (9) (MUST) |
| 648 | Replace Words | Python | O(n) | O(t) | Medium | Trie,good basic | OK* |
| 657 | Judge Route Circle | Python | O(n) | O(1) | Easy | OK | |
| 678 | Valid Parenthesis String | Python,Java | O(n) | O(1) | Medium | AGAIN** | |
| 680 | Valid Palindrome II | Python,Java | O(n) | O(1) | Easy | LC 125, two pointers,good basic, Palindrome,string,fb | AGAIN******** (3) |
| 681 | Next Closest Time | Python | O(1) | O(1) | Medium | subset of set,<=,strptime,google,fb | OK*** (5) |
| 686 | Repeated String Match | Python,Java | O(n + m) | O(1) | Medium | brute force, math, string,Rabin-Karp Algorithm,google | AGAIN**** (3) |
| 696 | Count Binary Substrings | Python | O(n) | O(1) | Easy | good trick, linear scan, group sub-string,amazon | AGAIN******* (3) (MUST) |
| 720 | Longest Word in Dictionary | Python | O(n) | O(t) | Easy | Trie | AGAIN (not start) |
| 722 | Remove Comments | Python,Java | O(n) | O(k) | Medium | string, google | AGAIN (1) |
| 734 | Sentence Similarity | Python,Java | O(n + p) | O(p) | Easy | good basic, graph,hash table,collections.defaultdict(set) ,google | OK***** (5) |
| 751 | IP to CIDR | Python | O(n) | O(1) | Medium | ip | AGAIN (not start*) |
| 758 | Bold Words in String | Python | O(n * l) | O(t) | Easy | 🔒, variant ofAdd Bold Tag in String | AGAIN (not start) |
| 791 | Custom Sort String | Python | O(n) | O(1) | Medium | good basic, sort, counter,amazon,fb | AGAIN************ (7) (MUST) |
| 796 | Rotate String | Python | O(n) | O(1) | Easy | good basic,KMP Algorithm,Rabin-Karp Algorithm,amazon | OK**** (2)(but again) |
| 804 | Unique Morse Code Words | Python | O(n) | O(n) | Easy | OK* | |
| 806 | Number of Lines To Write String | Python | O(n) | O(1) | Easy | OK* | |
| 809 | Expressive Words | Python,Java | O(n + s) | O(l + s) | Medium | google, string | AGAIN (1) |
| 816 | Ambiguous Coordinates | Python | O(n^4) | O(n) | Medium | AGAIN (not start*) | |
| 819 | Most Common Word | Python | O(m + n) | O(m + n) | Easy | regular expression,amazon | OK** (2) |
| 820 | Short Encoding of Words | Python | O(n) | O(t) | Medium | Trie | AGAIN (not start) |
| 824 | Goat Latin | Python | O(n + w^2) | O(l) | Easy | string basic,fb | OK |
| 828 | Count Unique Characters of All Substrings of a Given String | Python | O(n + w^2) | O(l) | Hard | LC 1248, dp,string,amazon | AGAIN*** (2) |
| 831 | Masking Personal Information | Python | O(1) | O(1) | Medium | regular expression | OK* |
| 833 | Find And Replace in String | Python,Java | O(n + m) | O(n) | Medium | good basic, string op, hashmap, google | AGAIN****** (3) |
| 848 | Shifting Letters | Python | O(n) | O(1) | Medium | remainder,basic | AGAIN** |
| 859 | Buddy Strings | Python | O(n) | O(1) | Easy | AGAIN* | |
| 880 | Decoded String at Index | Python | O(n) | O(1) | Medium | trick | AGAIN (not start**) |
| 884 | Uncommon Words from Two Sentences | Python | O(m + n) | O(m + n) | Easy | collections Counter,trick | OK* |
| 890 | Find and Replace Pattern | Python,Java | O(n * l) | O(1) | Medium | hashmap, pattern, LC 49 | AGAIN *** (3) |
| 893 | Groups of Special-Equivalent Strings | Python | O(n * l) | O(n) | Easy | AGAIN* | |
| 916 | Word Subsets | Python | O(m + n) | O(1) | Medium | AGAIN (not start) | |
| 917 | Reverse Only Letters | Python | O(n) | O(1) | Easy | basic,stack,pointer | OK* |
| 925 | Long Pressed Name | Python | O(n) | O(1) | Easy | two pointer,basic,trick | AGAIN* |
| 929 | Unique Email Addresses | Python | O(n * l) | O(n * l) | Easy | OK | |
| 939 | Minimum Area Rectangle | Python,Java | O(n^1.5) on average | O(n) | Medium | hashmap, brute force, google | AGAIN !!! (2) |
| 942 | DI String Match | Python | O(n) | O(1) | Easy | AGAIN (not start) | |
| 944 | Delete Columns to Make Sorted | Python | O(n * l) | O(1) | Medium | AGAIN (not start) | |
| 953 | Verifying an Alien Dictionary | Python,Java | O(n * l) | O(1) | Easy | AGAIN (not start) | |
| 955 | Delete Columns to Make Sorted II | Python | O(n * l) | O(n) | Medium | AGAIN (not start) | |
| 1119 | Remove Vowels from a String | Python | O(n * l) | O(n) | Easy | amazon | OK |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 281 | Zigzag Iterator | Python | O(n) | O(k) | Medium | good basic, queue, 🔒,google,fb | AGAIN******* (5) |
| 346 | Moving Average from Data Stream | Python,Java | O(1) | O(w) | Easy | 🔒, queue,google,fb | OK** (6) |
| 933 | Number of Recent Calls | Python | O(1) on average | O(w) | Easy | AGAIN** | |
| 622 | Design Circular Queue | Python,Java | Medium | good basic, array, linked list, design,circular queue,amazon,fb, apple, airbnb, m$ | AGAIN************ (3) (MUST) | ||
| 239 | Sliding Window Maximum | Python,Java | Hard | sliding window, heap, deque, queue,good trick,amazon,google | AGAIN************ (6) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 007 | Reverse Integer | Python | O(1) | O(1) | Medium | 0x7FFFFFFF, amazon, apple | OK* (3) |
| 009 | Palindrome Number | Python | O(1) | O(1) | Easy | amazon | OK |
| 012 | Integer to Roman | Python | O(n) | O(1) | Medium | math basic,twitter,fb, amazon, math | AGAIN****** (4) |
| 013 | Roman to Integer | Python,Java | O(n) | O(1) | Easy | good trick, map,UBER,amazon,fb | AGAIN***** (6) |
| 029 | Divide Two Integers | Python | O(1) | O(1) | Medium | binary search,trick,fb | AGAIN***** (3) |
| 050 | Pow(x, n) | Python,Java | O(1) | O(1) | Medium | good trick,amazon,fb, recursion | AGAIN****** (4) |
| 060 | Permutation Sequence | Python | O(n^2) | O(n) | Medium | Cantor Ordering,trick ,amazon | AGAIN*** (2) |
| 089 | Gray Code | Python | O(2^n) | O(1) | Medium | bit op, math,amazon | AGAIN ********** (6) |
| 166 | Fraction to Recurring Decimal | Python | O(logn) | O(1) | Medium | AGAIN (not start) | |
| 168 | Excel Sheet Column Title | Python,Java | O(logn) | O(1) | Easy | trick, residual, math, AGAIN,fb | AGAIN****** (5) |
| 171 | Excel Sheet Column Number | Python | O(n) | O(1) | Easy | AGAIN (not start) | |
| 172 | Factorial Trailing Zeroes | Python | O(1) | O(1) | Easy | basic,iteration,recursion | AGAIN* (2) |
| 223 | Rectangle Area | Python | O(1) | O(1) | Easy | AGAIN | |
| 258 | Add Digits | Python | O(1) | O(1) | Easy | AGAIN | |
| 263 | Ugly Number | Python | O(1) | O(1) | Easy | math | OK* (2) |
| 273 | Integer to English Words | Python | O(1) | O(1) | Hard | amazon, passed | not start |
| 292 | Nim Game | Python | O(1) | O(1) | Easy | LintCode | OK* |
| 319 | Bulb Switcher | Python | O(1) | O(1) | Medium | AGAIN | |
| 326 | Power of Three | Python | O(1) | O(1) | Easy | OK | |
| 338 | Counting Bits | Python,Java | O(n) | O(n) | Medium | Curated Top 75 | OK |
| 343 | Integer Break | Python,Java | O(logn) | O(1) | Medium | trick,DP | AGAIN* (2) |
| 365 | Water and Jug Problem | Python | O(logn) | O(1) | Medium | Bézout's identity | AGAIN (not start) |
| 372 | Super Pow | Python | O(n) | O(1) | Medium | AGAIN | |
| 382 | Linked List Random Node | Python | O(n) | O(1) | Medium | Reservoir Sampling | AGAIN (not start) |
| 386 | Lexicographical Numbers | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 390 | Elimination Game | Python | O(logn) | O(1) | Medium | AGAIN (not start) | |
| 398 | Random Pick Index | Python | O(n) | O(1) | Medium | Reservoir Sampling ,fb | OK* (4) |
| 400 | Nth Digit | Python | O(logn) | O(1) | Easy | AGAIN | |
| 413 | Arithmetic Slices | Python | O(n) | O(1) | Medium | sliding window,amazon | OK*** (1) (but again) |
| 423 | Reconstruct Original Digits from English | Python | O(n) | O(1) | Medium | GCJ2016 - Round 1B | AGAIN (not start) |
| 441 | Arranging Coins | Python | O(nlogn) | O(1) | Easy | Binary Search | OK |
| 453 | Minimum Moves to Equal Array Elements | Python | O(n) | O(1) | Easy | AGAIN | |
| 458 | Poor Pigs | Python | O(n) | O(1) | Easy | AGAIN | |
| 469 | Convex Polygon | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 470 | Implement Rand10() Using Rand7() | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 478 | Generate Random Point in a Circle | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 497 | Random Point in Non-overlapping Rectangles | Python | ctor:O(n) pick:O(logn) | O(n) | Medium | AGAIN (not start) | |
| 504 | Base 7 | Python | binary, math, good basic | O(n) | Easy | AGAIN******** (1) | |
| 519 | Random Flip Matrix | Python | ctor:O(1) pick:O(1) reset:O(n) | O(n) | Medium | AGAIN (not start) | |
| 528 | Random Pick with Weight | Python,Java | O(logn) | O(n) | Medium | good basic, binary search, prefix sum, google | AGAIN**** (1) |
| 537 | Complex Number Multiplication | Python | O(1) | O(1) | Medium | math,amazon | OK (3) |
| 553 | Optimal Division | Python | O(n) | O(1) | Medium | string, math,amazon | OK* (4) |
| 573 | Squirrel Simulation | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 592 | Fraction Addition and Subtraction | Python | O(nlogx) | O(n) | Medium | AGAIN | |
| 593 | Valid Square | Python,Java | O(1) | O(1) | Medium | google, math | AGAIN |
| 598 | Range Addition II | Python,Java | O(p) | O(1) | Easy | AGAIN | |
| 625 | Minimum Factorization | Python | O(loga) | O(1) | Medium | 🔒 | OK* |
| 628 | Maximum Product of Three Numbers | Python | O(n) | O(1) | Easy | amazon | OK (2) |
| 633 | Sum of Square Numbers | Python | O(sqrt(c) * logc) | O(1) | Easy | OK* | |
| 634 | Find the Derangement of An Array | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 640 | Solve the Equation | Python | O(n) | O(n) | Medium | math, regular expression,amazon | AGAIN*** (3) |
| 651 | 4 Keys Keyboard | Python | O(1) | O(1) | Medium | 🔒, Math, DP | AGAIN (not start) |
| 672 | Bulb Switcher II | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 728 | Self Dividing Numbers | Python | O(n) | O(1) | Medium | AGAIN | |
| 754 | Reach a Number | Python | O(logn) | O(1) | Medium | OK* | |
| 775 | Global and Local Inversions | Python | O(n) | O(1) | Medium | trick, math, string,amazon | AGAIN** (not start) (3) |
| 779 | K-th Symbol in Grammar | Python | O(1) | O(1) | Medium | math, brute force, binary, recursion, FB, amazon | AGAIN*** (1) |
| 781 | Rabbits in Forest | Python | O(n) | O(n) | Medium | AGAIN (not start) | |
| 789 | Escape The Ghosts | Python | O(n) | O(1) | Medium | AGAIN | |
| 800 | Similar RGB Color | Python | O(1) | O(1) | Easy | 🔒 | AGAIN (not start) |
| 812 | Largest Triangle Area | Python | O(n^3) | O(1) | Easy | AGAIN (not start) | |
| 829 | Consecutive Numbers Sum | Python | O(sqrt(n)) | O(1) | Medium | AGAIN | |
| 836 | Rectangle Overlap | Python | O(1) | O(1) | Easy | similar as 223. Rectangle Area,amazon | AGAIN (2) |
| 858 | Mirror Reflection | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 866 | Prime Palindrome | Python | O(n^(1/2) * (logn + n^(1/2))) | O(logn) | Medium | AGAIN*** | |
| 867 | Transpose Matrix | Java | O(n^(1/2) * (logn + n^(1/2))) | O(logn) | Medium | AGAIN* | |
| 883 | Projection Area of 3D Shapes | Python | O(n^2) | O(1) | Easy | AGAIN | |
| 891 | Sum of Subsequence Widths | Python | O(n^2) | O(1) | Hard | amazon | AGAIN (not start) |
| 907 | Sum of Subarray Minimums | Python | O(n) | O(n) | Medium | trick, LC 084, LC 2104, Ascending Stack,amazon | AGAIN**** (1) |
| 908 | Smallest Range I | Python | O(n) | O(1) | Easy | OK* (2) | |
| 910 | Smallest Range II | Python | O(nlogn) | O(1) | Medium | AGAIN (not start) | |
| 914 | X of a Kind in a Deck of Cards | Python | O(n * (logn)^2) | O(n) | Easy | AGAIN (not start) | |
| 963 | Minimum Area Rectangle II | Python | O(n^2) ~O(n^3) | O(n^2) | Medium | AGAIN (not start) | |
| 970 | Powerful Integers | Python | O((logn)^2) | O(r) | Easy | basic | AGAIN* (2) |
| 517 | Super Washing Machines | Python | Hard | amazon | AGAIN (not start) | ||
| 1071 | Greatest Common Divisor of Strings | Java | O(n^2) ~O(n^3) | O(n^2) | Easy | AGAIN (not start) | |
| 1342 | Number of Steps to Reduce a Number to Zero | Python | easy | gra* | ok | ||
| 1492 | The kth Factor of n | Python | Medium | amazon | AGAIN (not start) | ||
| 1979 | Find Greatest Common Divisor of Array | Python | Easy | GCD | not start | ||
| 2013 | Detect Squares | Java | Medium | math | not start | ||
| 2507 | Smallest Value After Replacing With Sum of Prime Factors | Java | Medium | math, LC weekly | again (1) | ||
| 2807 | Insert Greatest Common Divisors in Linked List | Java | Medium | math | OK | ||
| 3190 | Find Minimum Operations to Make All Elements Divisible by Three | Java | Easy | LC weekly, math | OK | ||
| 3194 | Minimum Average of Smallest and Largest Elements | Java | Easy | LC weekly, math | OK |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 075 | Sort Colors | Python,Java | O(n) | O(1) | Medium | sorting, Tri Partition,two pointers,M$,fb | OK** (4) |
| 088 | Merge Sorted Array | Python,Java | O(n) | O(1) | Easy | good basic, merge, sort,two pointers,M$,amazon,fb | AGAIN************* (8) (MUST) |
| 128 | Longest Consecutive Sequence | Python,Java | Medium | Curated Top 75, 2 pointers, sort, sliding window,amazon | AGAIN*********** (4) (MUST) | ||
| 147 | Insertion Sort List | Python | O(n^2) | O(1) | Medium | trick | AGAIN* (2) |
| 148 | Sort List | Python | O(nlogn) | O(logn) | Medium | basic, check# 21 Merge Two Sorted Lists | AGAIN** (2) |
| 179 | Largest Number | Python | O(nlogn) | O(1) | Medium | good basic, sort with lambda,amazon | AGAIN************ (3) |
| 252 | Meeting Rooms | Python,Java | O(nlogn) | O(n) | Easy | Curated Top 75, sort, 🔒,UBER,amazon,fb | OK*** (4) (but again) |
| 253 | Meeting Rooms II | Python,Java | O(nlogn) | O(n) | Medium | Curated Top 75, 🔒, sort, priority queue (min-heap),scanning line,trick,booking.com,good,UBER,amazon,google,fb | AGAIN************ (5) (MUST) |
| 274 | H-Index | Python | O(n) | O(n) | Medium | Counting Sort,good trick,fb | AGAIN***** (3) |
| 280 | Wiggle Sort | Python | O(n) | O(1) | Medium | 🔒,google,fb | OK*** (3) |
| 324 | Wiggle Sort II | Python | O(n) on average | O(1) | Medium | variant ofSort Colors , Tri Partition,google | AGAIN** (2) |
| 347 | Top K Frequent Elements | Python,Java | O(n) | O(n) | Medium | Curated Top 75 , HashMap, Heap, Sort,Yelp,amazon,fb, GOOD basic | AGAIN******** (4) |
| 406 | Queue Reconstruction by Height | Python,Java | O(n * sqrt(n)) | O(n) | Medium | basic,trick,sort by key,insert,google, next_big_val | AGAIN********* (5) |
| 451 | Sort Characters By Frequency | Python,Java | O(n) | O(n) | Medium | collections.Counter(s).most_common,sorted(count_dict.items() with lambda,good basic,amazon | OK* (4) |
| 692 | Top K Frequent Words | Python,Java | O(n + klogk) on average | O(n) | Medium | good basic,Quick Select, Heap, Bucket Sort,heapq,yelp,UBER,amazon,fb | OK***** (5) |
| 937 | Reorder Data in Log Files | Python | O(nlogn * l) | O(l) | Medium | good basic, sort,string,amazon | OK**** (3)(again!!!) |
| 969 | Pancake Sorting | Python | O(n^2) | O(l) | Medium | fb, sorting | AGAIN********** (4) |
| 973 | K Closest Points to Origin | Python,Java | O(n) on average | O(1) | Medium | good trick, sort with func, PQ, Heap,amazon | OK***** (3)(but again) |
| 976 | Largest Perimeter Triangle | Python,Java | O(nlogn) | O(1) | Easy | OK* (2) | |
| 912 | Sort an Array | Python,Java | O(nlogn) | O(1) | Medium | sort, merge sort, quick sort, apple, amazon, m$ | AGAIN** (1) |
| 1057 | Campus Bike | Java | O(nlogn) | O(1) | Medium | sorting, google | AGAIN |
| 1066 | Campus Bike II | Java | O(nlogn) | O(1) | Medium | sorting, google | AGAIN |
| 1152 | Analyze User Website Visit Pattern | Python | O(nlogn) | O(1) | Medium | itertools.combinations, sort, brute force, set,amazon | AGAIN***** (2) (not start) |
| 2021 | Brightest Position on Street | Python | O(nlogn) | O(1) | Medium | LC 253 meeting room II, priority queue (min-heap), scanning line, trick,amazon | AGAIN*********** (3) (MUST) |
| 2284 | Sender With Largest Word Count | Java | O(1) | Medium | LC 347, map sorting | OK | |
| 2402 | Meeting Rooms III | Java | O(nlogn) | O(n) | Hard | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 019 | Remove Nth Node From End of List | Python,Java | O(n) | O(1) | Medium | Curated Top 75, good basic, MUST,linked list,two pointers,fb | AGAIN********** (4) (MUST) |
| 042 | Trapping Rain Water | Python,Java | Hard | stack, prefix-suffix array, brute force, two pointer,amazon,apple | AGAIN******** (3) | ||
| 086 | Partition List | Python,Java | O(n) | O(1) | Medium | OK* | |
| 141 | Linked List Cycle | Python,Java | O(n) | O(1) | Easy | Curated Top 75,basic,amazon,fb, linked list, 2 pointers, check #142 | OK** (5) |
| 142 | Linked List Cycle II | Python,Java | O(n) | O(1) | Medium | linked list, 2 pointers, check #141 | AGAIN****** (4) (again!) |
| 143 | Reorder List | Python,Java | O(n) | O(1) | Medium | Curated Top 75, LC 021, 206, 876,good trick,inverse linkedlist,merge linkedlist ,fb, amazon | AGAIN********** (5) (MUST) |
| 167 | Two Sum II - Input array is sorted | Python,Java | O(n) | O(1) | Medium | two pointer, dict, binary search,good basic,amazon | OK* (6) |
| 259 | 3Sum Smaller | Python | O(n^2) | O(1) | Medium | 🔒, LintCode,good trick,google,fb, check#015 3 Sum, check#001 two sum | AGAIN******** (4) |
| 283 | Move Zeroes | Python,Java | O(n) | O(1) | Easy | basic,trick, ,two pointers,Shopee,fb | AGAIN** (5) |
| 344 | Reverse String | Python | O(n) | O(1) | Easy | OK | |
| 345 | Reverse Vowels of a String | Python,Java | O(n) | O(1) | Easy | google | OK** (1) |
| 349 | Intersection of Two Arrays | Python | O(m + n) | O(min(m, n)) | Easy | EPI, Hash, Binary Search,fb | OK |
| 350 | Intersection of Two Arrays II | Python | O(m + n) | O(1) | Easy | EPI, Hash, Binary Search,good basic,fb | OK** (3) |
| 360 | Sort Transformed Array | Python | O(n) | O(1) | Medium | trick,🔒,google ,fb | AGAIN*** (3) |
| 457 | Circular Array Loop | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 567 | Permutation in String | Python,Java | O(n) | O(1) | Medium | Collections.counter,sliding window, sorting, hashmap,substring,good basic,M$,fb | AGAIN********* (8) |
| 611 | Valid Triangle Number | Python | O(n^2) | O(1) | Medium | AGAIN (not start) | |
| 777 | Swap Adjacent in LR String | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 826 | Most Profit Assigning Work | Python | O(mlogm + nlogn) | O(n) | Medium | trick,good basic,zip+sorted | OK* |
| 844 | Backspace String Compare | Python,Java | O(m + n) | O(1) | Easy | good basic,stack,google,fb | OK* (4) |
| 876 | Middle of the Linked List | Python,Java | O(n) | O(1) | Easy | basic, amazon, apple, google, 2 pointers, linkedlist | OK* (2) |
| 904 | Fruit Into Baskets | Python,Java | O(n) | O(1) | Medium | 2 pointers, google | AGAIN (not start) |
| 930 | Binary Subarrays With Sum | Python | O(n) | O(1) | Medium | trick | AGAIN* (2) (not start) |
| 977 | Squares of a Sorted Array | Python | O(n) | O(1) | Easy | OK | |
| 986 | Interval List Intersections | Java | O(n) | O(1) | Medium | 2 pointer, scanning line, good basic, google | AGAIN********* (1) (MUST) |
| 1055 | Shortest Way to Form String | Python,Java | O(n) | O(h) | Medium | 2 pointer,google | again |
| 1151 | Minimum Swaps to Group All 1's Together | Python | O(n) | O(1) | Medium | good basic, 2 pointers, Deque (Double-ended Queue),amazon | AGAIN***** (not start ) |
| 1768 | Merge Strings Alternately | Java | O(n) | O(h) | Easy | tree,recursion,google | OK |
| 1963 | Minimum Number of Swaps to Make the String Balanced | Python | O(n) | O(h) | Medium | good basic, greedy, stack, 2 pointers, amazon, fb, m$ | AGAIN******** (2) |
| 3191 | Minimum Operations to Make Binary Array Elements Equal to One I | Java | O(n) | O(h) | Medium | 2 pointers | Again* (2) |
| 3192 | Minimum Operations to Make Binary Array Elements Equal to One II | Java | O(n) | O(h) | Medium | 2 pointers | Again* (2) |
| # | Title | Solution | Time | Space | Difficulty | Note | Status |
|---|---|---|---|---|---|---|---|
| 10 | Regular Expression Matching | Python | O(n) | O(h) | Hard | recursive, dp,amazon | AGAIN (not start) |
| 095 | Unique Binary Search Trees II | Python | O(4^n / n^(3/2) | O(4^n / n^(3/2) | Medium | recursion, BST, amazon, google, apple | AGAIN!!! (1)(good trick) |
| 098 | Validate Binary Search Tree | Python,Java | O(n) | O(1) | Medium | Curated Top 75, recursion, bfs, dfs,BST,M$,amazon,fb | AGAIN****************** (11) |
| 100 | Same Tree | Python,Java | O(n) | O(h) | Easy | Curated Top 75, recursion, dfs, bfs,good basic,amazon | OK****** (5) (but again) |
| 104 | Maximum Depth of Binary Tree | Python,Java | O(n) | O(h) | Easy | Curated Top 75, DFS, BFS, good basic,amazon, LC 111 | OK******** (5) (but again) |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | Python,Java | O(n) | O(n) | Medium | Curated Top 75,trick, check # 106,BST,M$,fb | AGAIN********* (9) |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | Python,Java | O(n) | O(n) | Medium | trick,check # 105,BST,M$,fb | AGAIN******* (6) |
| 108 | Convert Sorted Array to Binary Search Tree | Python,Java | O(n)O(logn) | Easy | good basic, BST, build tree, DFS | AGAIN********* (1) (must) | |
| 109 | Convert Sorted List to Binary Search Tree | Python | O(n) | O(logn) | Medium | list,BST,good concept,fb | AGAIN*** (3) |
| 110 | Balanced Binary Tree | Python,Java | O(n) | O(h) | Easy | good trick,LC 104,dfs,bfs,amazon ,fb, google, top-down, bottom-up recursion | AGAIN************** (8)(MUST) |
| 111 | Minimum Depth of Binary Tree | Python,Java | O(n) | O(h) | Easy | good basic,dfs,BST,amazon,fb, LC 104 | AGAIN******** (5) |
| 114 | Flatten Binary Tree to Linked List | Python,Java | O(n) | O(h) | Medium | BST,dfs,M$,fb | AGAIN**** (4) |
| 116 | Populating Next Right Pointers in Each Node | Python,Java | O(n) | O(1) | Medium | good basic, bfs, dfs, tree, recursion ,AGAIN,fb, amazon | AGAIN************ (6) |
| 117 | Populating Next Right Pointers in Each Node II | Python,Java | O(n) | O(h) | Medium | good basic, prev node,Populating Next Right Pointers in Each Node I, bfs, linked list,amazon,fb, google | AGAIN************* (4) |
| 129 | Sum Root to Leaf Numbers | Python,Java | O(n) | O(h) | Medium | path sum,trick,BST,dfs,fb | AGAIN*** (4) |
| 156 | Binary Tree Upside Down | Python | O(n) | O(1) | Medium | 🔒 | AGAIN (not start) |
| 241 | Different Ways to Add Parentheses | Python,Java | O(n * 4^n / n^(3/2)) | O(n * 4^n / n^(3/2)) | Medium | complex, dp, recursion, Memoization, google | AGAIN (not start) |
| 298 | Binary Tree Longest Consecutive Sequence | Python,Java | O(n) | O(h) | Medium | LC 437, good basic, bfs, dfs, tree, 🔒,google | AGAIN ********* (4) (must) |
| 333 | Largest BST Subtree | Python | O(n) | O(h) | Medium | 🔒 | AGAIN (not start) |
| 337 | House Robber III | Python,Java | O(n)O(h) | Medium | good trick, dp + dfs, amazon, google | AGAIN****** (2)(MUST) | |
| 395 | Longest Substring with At Least K Repeating Characters | Python,Java | O(n) | O(1) | Medium | slide window,DIVIDE AND CONQUER,good trick,fb, google | AGAIN************ (4) |
| 404 | Sum of Left Leaves | Python,Java | O(n) | O(h) | Easy, tree, bfs, dfs, amazon | AGAIN**** (4) | |
| 437 | Path Sum III | Python,Java | O(n) | O(h) | Medium | LC 298, path sum,good trick,UBER,AMAZON,fb | AGAIN******** (4) (must) |
| 501 | Find Mode in Binary Search Tree | Java | O(n) | O(h) | Medium | dfs, bfs, LC 98 | OK (1) |
| 544 | Output Contest Matches | Python | O(n) | O(n) | Medium | AGAIN | |
| 549 | Binary Tree Longest Consecutive Sequence II | Python | O(n) | O(h) | Medium | 🔒 | AGAIN (not start) |
| 669 | Trim a Binary Search Tree | Python | O(n) | O(h) | Medium | good basic, BST, dfs, recursion,amazon | AGAIN******* (4) |
| 671 | Second Minimum Node In a Binary Tree | Python | O(n) | O(h) | Easy | dfs,tree | OK* (2) |
| 753 | Cracking the Safes | Java | O(n) | O(h) | Hard | dfs,recursion,google | AGAIN (not start) |
| 1145 | Binary Tree Coloring Game | Java | O(n) | O(h) | Medium | tree,recursion,google | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Tag, Note | Status |
|---|---|---|---|---|---|---|---|
| 33 | Search in Rotated Sorted Array | Python,Java | Medium | Curated Top 75,binary search, LC 153,good basic ,check# 81 Search in Rotated Sorted Array II, binary search, rotation array,UBER,amazon,fb | AGAIN************ (6) (MUST) | ||
| 034 | Find First and Last Position of Element in Sorted Array | Python,Java | O(n) | O(1) | Medium | binary search, LC top 100 like,amazon,fb, google, apple, uber | AGAIN************** (4) (MUST) |
| 034 | Search for a Range | Python | O(logn) | O(1) | Medium | AGAIN* | |
| 035 | Search Insert Position | Python,Java | O(logn) | O(1) | Medium | AGAIN | |
| 069 | Sqrt(x) | Python | O(logn) | O(1) | Medium | math, binary search,amazon,fb | OK* (4) |
| 074 | Search a 2D Matrix | Python,Java | O(logm + logn) | O(1) | Medium | binary search in 2D array, flatten matrix,amazon | OK**** (BUT AGAIN)(3) |
| 081 | Search in Rotated Sorted Array II | Python,Java | O(logn) | O(1) | Medium | binary search,check# 33 Search in Rotated Sorted Array first,array,fb, amazon, linkedin | OK***** (6) |
| 153 | Find Minimum in Rotated Sorted Array | Python,Java | O(logn) | O(1) | Medium | Curated Top 75, LC 33, binary search, ascending array, good basic,amazon | AGAIN************* (8)(MUST) |
| 154 | Find Minimum in Rotated Sorted Array II | Java | O(logn) | O(1) | Medium | LC 153, binary search | AGAIN (not start) |
| 162 | Find Peak Element | Python,Java | O(logn) | O(1) | Medium | good trick, recursive, iterative binary search,M$,google,fb | AGAIN********** (6) |
| 222 | Count Complete Tree Nodes | Python,Java | O((logn)^2) | O(1) | Easy | google, tree | OK (again) |
| 275 | H-Index II | Python | O(logn) | O(1) | Medium | similar as# 274 H-Index, Binary Search,fb | AGAIN**** (3) |
| 278 | First Bad Version | Python,Java | O(logn) | O(1) | Easy | good basic,LintCode, binary search,fb | OK*** (5) (MUST) |
| 300 | Longest Increasing Subsequence | Python,Java | O(nlogn) | O(n) | Medium | Curated Top 75, array, binary search,DP good basic, LintCode, DP,amazon,fb | AGAIN********** (10) |
| 315 | Count of Smaller Numbers After Self | Python,Java | O(logn) | O(1) | Hard | binary search, BST, BIT,google | again* |
| 367 | Valid Perfect Square | Python,Java | O(logn) | O(1) | Easy | good basic, similar as# 69 Sqrt(x) | OK* (3) |
| 374 | Guess Number Higher or Lower | Python,Java | O(logn) | O(1) | Easy | OK* | |
| 410 | Split Array Largest Sum | Python,Java | O(logn) | O(1) | Hard | AGAIN (not start) | |
| 436 | Find Right Interval | Python | O(nlogn) | O(n) | Medium | AGAIN (not start) | |
| 475 | Heaters | Python | O((m + n) * logn) | O(1) | Easy | AGAIN (not start) | |
| 540 | Single Element in a Sorted Array | Python,Java | O(logn) | O(1) | Medium | OK* | |
| 564 | Find the Closest Palindrome | Java | O(logn) | O(1) | Hard | AGAIN(not start) | |
| 658 | Find K Closest Elements | Python,Java | O(logn + k) | O(1) | Medium | good trick, PQ,two pointers,binary search,amazon,fb, google | AGAIN ****************** (7) (MUST) |
| 744 | Find Smallest Letter Greater Than Target | Python | O(logn) | O(1) | Easy | OK* | |
| 852 | Peak Index in a Mountain Array | Python,Java | O(logn) | O(1) | Medium | LC 162 Find Peak Element,amazon, google | OK* (2) |
| 875 | Koko Eating Bananas | Python,Java | O(nlogr) | O(1) | Medium | binary search, left boundary, good basic | AGAIN******* (4)(MUST) |
| 894 | All Possible Full Binary Trees | Python | O(n * 4^n / n^(3/2)) | O(n * 4^n / n^(3/2)) | Medium | AGAIN (not start) | |
| 911 | Online Election | Python | ctor:O(n) query :O(logn) | O(n) | Medium | AGAIN (not start) | |
| 981 | Time Based Key-Value Store | Python,Java | O(n) | Medium | binary search, dict, treeMap, floorKey, sort, apple, M$, amz, google | AGAIN****** (2) | |
| 1011 | Capacity To Ship Packages Within D Days | Python,Java | Medium | good trick, binary search, amazon, apple, fb, m$, google | AGAIN****** (3) | ||
| 1060 | Missing Element in Sorted Array | Java | Medium | binary search, brute force, good trick, google | AGAIN**** (2) | ||
| 1095 | Find in Mountain Array | Java | Hard | AGAIN (not start) | |||
| 1889 | Minimum Space Wasted From Packaging | Python | Hard | heap, prefix sum, binary search, amazon | AGAIN (not start) | ||
| 2009 | Minimum Number of Operations to Make Array Continuous | Python | Hard | binary search, sliding window, dequeue, bisect.bisect_right, amazon | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Tag,Note | Status |
|---|---|---|---|---|---|---|---|
| 220 | Contains Duplicate III | Python | O(nlogk) | O(k) | Medium | AGAIN (not start) | |
| 230 | Kth Smallest Element in a BST | Python,Java | O(max(h, k)) | O(min(h, k)) | Medium | Curated Top 75, good basic BST basic, DFS, BFS, STACK, BST,amazon | OK********* (4) |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Python,Java | O(h) | O(1) | Medium | Curated Top 75, BST, recursion, iteration, good basic,LCA, check# 236 Lowest Common Ancestor of a Binary Tree,amazon,fb | OK**************** (but again)(10) |
| 270 | Closest Binary Search Tree Value | Python | O(h) | O(1) | Easy | good basic ,🔒,M$, BST,google,fb | OK***** (5) |
| 285 | Inorder Successor in BST | Python | O(h) | O(1) | Medium | BST, dfs, good basic, 🔒,amazon,fb | OK** (4) |
| 449 | Serialize and Deserialize BST | Python | O(n) | O(h) | Medium | LC 297, dfs, bfs, good trick,serizlize deserizlize, tree,amazon,fb | AGAIN************* (9) (MUST) |
| 450 | Delete Node in a BST | Python,Java | O(h) | O(h) | Medium | good trick, BST, tree, dfs, LC 1325 | AGAIN***************** (9) (MUST !!!) |
| 510 | Inorder Successor in BST II | Java | O(h) | O(h) | Medium | BST, parent | AGAIN** (1) (not start) |
| 530 | Minimum Absolute Difference in BST | Python,Java | O(n) | O(h) | Easy | LC 783 | AGAIN* |
| 700 | Search in a Binary Search Tree | Python,Java | O(n) | O(h) | Easy | BST, good basic, recursion, iteration amazon | AGAIN*** (1) |
| 776 | Split BST | Python,Java | O(n) | O(h) | Medium | 🔒, BST, DFS, trick, AGAIN ,amazon, google | AGAIN********* (6) |
| 783 | Minimum Distance Between BST Nodes | Python | O(n) | O(h) | Easy | LC 530 | OK* |
| 426 | Convert Binary Search Tree to Sorted Doubly Linked List | Python | Medium | recursion, tree,linked list,good basicUBER,lyft,amazon,google,fb | AGAIN******* (5) (not start) | ||
| 968 | Binary Tree Cameras | Python | O(n) | Hard | amazon, dfs, bst, dp, greedy, m$ | AGAIN (not start) | |
| 1022 | Sum of Root To Leaf Binary Numbers | Python | O(n) | Easy | good basic, LC 257, bst path, dfs, bfs,amazon | AGAIN******** (1) (MUST) | |
| 1597 | Build Binary Expression Tree From Infix Expression | Python | O(n) | Hard | LC 224, recursive, iteration, stack,amazon, google, bst | AGAIN*** (1) | |
| 1644 | Lowest Common Ancestor of a Binary Search Tree 2 | Java | O(h) | O(1) | Medium | LC 235, 236, dfs | AGAIN (1) |
| 1650 | Lowest Common Ancestor of a Binary Search Tree 3 | Java | O(h) | O(1) | Medium | LC 235, 236, dfs | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Tag | Status |
|---|---|---|---|---|---|---|---|
| 102 | Binary Tree Level Order Traversal | Python,Java | O(n) | O(n) | Easy | Curated Top 75,GOOD basic,dfs,bfs,UBER,apple,amazon,fb, LC 199 | AGAIN******* (8) (must) |
| 107 | Binary Tree Level Order Traversal II | Python,Java | O(n) | O(n) | Easy | same as# 102 Binary Tree Level Order Traversal | OK* (3) |
| 103 | Binary Tree Zigzag Level Order Traversal | Python | O(n) | O(n) | Medium | amazon,fb | OK |
| 126 | Word Ladder II | Python,Java | Hard | complex, trick, dfs, bfs, dfs+bfs, check# 127 Word Ladder,amazon | AGAIN*** (3) (not start) | ||
| 127 | Word Ladder | Python,Java | O(n * d) | O(d) | Hard/Medium | good basic, check #126 Word Ladder II,bfs,UBER,amazon,M$,fb | AGAIN************** (10) |
| 130 | Surrounded Regions | Python,Java | O(m + n) | Medium | bfs,dfs,union find,good basic,amazon | AGAIN*********** (5) | |
| 133 | Clone Graph | Python,Java | O(n) | O(n) | Medium | Curated Top 75, good trick, LC 138,graph,dfs,bfs,UBER,google,amazon,fb | AGAIN**************** (11) (MUST) |
| 207 | Course Schedule | Python,Java | O(|V| + |E|) | O(|E|) | Medium | Curated Top 75, Topological Sort, LC 210,good trick,dfs,bfs ,amazon,fb | AGAIN**************** (15) (MUST) |
| 210 | Course Schedule II | Python,Java | O(|V| + |E|) | O(|E|) | Medium | Topological Sort,LC 207, dfs ,amazon ,fb | AGAIN********* (10) (again) |
| 261 | Graph Valid Tree | Python,Java | O(|V| + |E|) | O(|V| + |E|) | Medium | Curated Top 75, AGAIN, bfs, dfs, grpah, 🔒,graph,quick union,union find ,google,amazon,fb | AGAIN************* (11)(MUST) |
| 286 | Walls and Gates | Python,Java | O(m * n) | O(g) | Medium | 🔒,dfs,bfs ,good basic,google,amazon,FB | AGAIN******** (8) |
| 310 | Minimum Height Trees | Python,Java | O(n) | O(n) | Medium | complex,bfs,google | AGAIN (4) |
| 433 | Minimum Genetic Mutation | Python | O(n * b) | O(b) | Medium | check# 127 Word Ladder,good basic | AGAIN*** (3) |
| 444 | Sequence Reconstruction | Python,Java | O(n * s) | O(n) | Medium | good trick,Topological Sort ,google,airbnb | AGAIN******* (4) (not start) |
| 490 | The Maze | Python | O(max(r, c) * w) | O(w) | Medium | basic,bfs,dfs,amazon,fb | AGAIN**** (5) |
| 505 | The Maze II | Python | O(max(r, c) * wlogw) | O(w) | Medium | trick,bfs,dfs,AGAIN,google,fb | AGAIN********* (6) |
| 542 | 01 Matrix | Python,Java | O(m * n) | O(m * n) | Medium | multi-source BFS, google | AGAIN*** (3) |
| 666 | Path Sum IV | Python | O(n) | O(w) | Medium | 🔒 Topological Sort | AGAIN* (3) (not start) |
| 742 | Closest Leaf in a Binary Tree | Python,Java | O(n) | O(n) | Medium | AGAIN, Graph, bfs+dfs, search,good trick,amazon | AGAIN********** (6) |
| 743 | Network Delay Time | Python,Java | O(n) | O(n) | Medium | Dijlstra, shortest path in parallel,google | AGAIN **** (3) |
| 752 | Open the Lock | Python,Java | O(k * n^k + d) | O(k * n^k + d) | Medium | LC 863, google | AGAIN (not start) |
| 787 | Cheapest Flights Within K Stops | Python,Java | O(|E| * log|V|) | O(|E|) | Medium | Dijkstra's algorithm, dfs, bfs, graph, priority queue,amazon, apple, google, airbnb | AGAIN****** (4) |
| 815 | Bus Routes | Python,Java | O(|E| * log|V|) | O(|E|) | Hard | shortest route, graph, bfs,amazon, google | AGAIN**** (3) |
| 886 | Possible Bipartition | Python | O(|V| + |E|) | O(|V| + |E|) | Medium | check# 785 Is Graph Bipartite?,graph,AGAIN,union find ,fb | AGAIN********** (6) |
| 934 | Shortest Bridge | Python,Java | O(n^2) | O(n^2) | Medium | BFS, DFS,complex, dfs,bfs,google | AGAIN (1) |
| 967 | Numbers With Same Consecutive Differences | Python | O(2^n) | O(2^n) | Medium | good trick | AGAIN** (3) |
| 675 | Cut Off Trees for Golf Event | Python,Java | Hard | tree, BFS, complex,amazon | AGAIN (not start) | ||
| 864 | Shortest Path to Get All Keys | Python | Hard | BFS,amazon | AGAIN (not start) | ||
| 1091 | Shortest Path in Binary Matrix | Java | Medium | BFS,google | AGAIN (not start) | ||
| 994 | Rotting Oranges | Python,Java | Medium | BFS, dpamazon | OK** (2) | ||
| 1110 | Delete Nodes And Return Forest | Python,Java | Medium | BFS, recursivegoogle | not start | ||
| 1162 | As Far from Land as Possible | Python | Medium | dfs, bfs, good basic,amazon | AGAIN**** (3) | ||
| 1197 | Minimum Knight Moves | Java | Medium | BFS,google | OK (1) | ||
| 1730 | Shortest Path to Get Food | Python | Medium | shortest path, bfs,amazon | OK (2) | ||
| 2115 | Find All Possible Recipes from Given Supplies | Java | Medium | bfs, dfs, topological sort,google | OK (2) |
| # | Title | Solution | Time | Space | Difficulty | Tag | Status |
|---|---|---|---|---|---|---|---|
| 112 | Path Sum | Python,Scala,Java | O(n) | O(h) | Easy | good concept,amazon, dfs, recursion | AGAIN** (2) |
| 113 | Path Sum II | Python,Java | O(n) | O(h) | Medium | dfs, backtrack, good basic, LC112 Path Sum,good basic,amazon,fb | AGAIN********* (7) |
| 199 | Binary Tree Right Side View | Python,Java | O(n) | O(h) | Medium | good basic,dfs,bfs,apple,amazon,fb, LC 102 | OK*** (6) |
| 200 | Number of Islands | Python,Java | O(m * n) | O(m * n) | Medium | Curated Top 75,bfs,dfs,good basic,check# 694, 711 Number of Distinct Islands,apple,Goldman Sachs,google,amazon,fb | OK****** (6) |
| 236 | Lowest Common Ancestor of a Binary Tree | Python,Java | O(n) | O(h) | Medium | trick,EPI,LCA, LC 1644, 235,apple,amazon,linkedin,fb | AGAIN************* (9) |
| 247 | Strobogrammatic Number II | Python,Java | O(n^2 * 5^(n/2)) | O(n) | Medium | 🔒,check#246 Strobogrammatic Number,good trick,google,fb | AGAIN******** (5) |
| 257 | Binary Tree Paths | Python,Java | O(n * h) | O(h) | Easy | good basic,apple,google,amazon,fb, iterative, dfs, LC 112, 113 | AGAIN********* (MUST) (7) |
| 332 | Reconstruct Itinerary | Python,Java | O(t! / (n1! * n2! * ... nk!)) | O(t) | Medium | DFS,yelp,google | AGAIN* (3) (not start) |
| 339 | Nested List Weight Sum | Python | O(n) | O(h) | Easy | 🔒,good basic,bfs,linkedin,fb | AGAIN*** (3) |
| 364 | Nested List Weight Sum II | Python | O(n) | O(h) | Medium | 🔒,linkedin | AGAIN* |
| 366 | Find Leaves of Binary Tree | Python | O(n) | O(h) | Medium | 🔒,linkedin | AGAIN* |
| 399 | Evaluate Division | Python,Java | O(q * |V|!) | O(e) | Medium | good trick,union find,dfs,good trick,union findgoogle,fb | AGAIN*********** (8) |
| 417 | Pacific Atlantic Water Flow | Python,Java | O(m * n) | O(m * n) | Medium | Curated Top 75, 2 direction dfs, dfs, matrix,m$,google | AGAIN** (3) |
| 464 | Can I Win | Python | O(n!) | O(n) | Medium | DP,linkedin | AGAIN* (not start) |
| 491 | Increasing Subsequences | Python | Medium | trick,dfs,dfs good trick,dp,yahoo ,fb | AGAIN***** (2) | ||
| 515 | Find Largest Value in Each Tree Row | Python | O(n) | O(h) | Medium | good basic,linkedin | AGAIN* (3) |
| 529 | Minesweeper | Python,Java | Medium | dfs, bfs, good basic, dfs, bfs,amazon,google | AGAIN**** (5) | ||
| 547 | Friend Circles | Python | O(n^2) | O(n) | Medium | graph, Union Find,dfs, bfs,check# 733 Flood Fill,bloomberg ,fb | AGAIN*** (3) (not start) |
| 547 | Number of Provinces | Python | O(n^2) | O(n) | Medium | dfs, bfs, graph, union find, good basic, apple, amazon | AGAIN************ (2) (MUST) |
| 582 | Kill Process | Python | O(n) | O(n) | Medium | 🔒, DFS, BFS,good basic ,bloomberg,amazon | AGAIN***** (4) |
| 638 | Shopping Offers | Python | O(n * 2^n) | O(n) | Medium | google | AGAIN (not start*) |
| 690 | Employee Importance | Python | O(n) | O(h) | Easy | DFS, BFS,good basic ,UBER | OK** (3) |
| 694 | Number of Distinct Islands | Python | O(m * n) | O(m * n) | Medium | #200, #711 Number of Islands good pattern, dfs, 🔒, compare with# 200 Number of Islands,amazon | AGAIN******** (5) |
| 695 | Max Area of Island | Python,Java | O(m * n) | O(m * n) | Medium | dfs, primitives in java,amazon,microsoft,linkedin,basic | AGAIN* (3) |
| 711 | Number of Distinct Islands II | Python,Java | Hard | complex, dfs, check# 200, 694 Number of Distinct Islands,amazon | OK*** (3) | ||
| 721 | Accounts Merge | Python,Java | O(nlogn) | O(n) | Medium | dfs, Disjoint Set Union (DSU),Union Find,path compression,complex,fb, google, amazon, m$, apple, twitter | AGAIN******* (4) (not start) |
| 733 | Flood Fill | Python | O(m * n) | O(m * n) | Easy | fb,amazon,good basic | OK**** (5) |
| 737 | Sentence Similarity II | Python,Java | O(m * n) | O(m * n) | Medium | dfs, union find, dis-joint,google | AGAIN**** (2) |
| 756 | Pyramid Transition Matrix | Python | O(a^b) | O(a^b) | Medium | AGAIN (3) (not start) | |
| 785 | Is Graph Bipartite? | Python | O(|V| + |E|) | O(|V|) | Medium | check #886 Possible Bipartition,AGAIN,graph,dfs,fb,amazon | AGAIN*********** (6) |
| 797 | All Paths From Source to Target | Python | O(p + r * n) | O(n) | Medium | graph,dfs classics,good basic | AGAIN** (3) |
| 802 | Find Eventual Safe States | Python,Java | O(|V| + |E|) | O(|V|) | Medium | Topological Sort, dfs, bfd, graph, google | AGAIN (4) (not start) |
| 841 | Keys and Rooms | Python | O(n!) | O(n) | Medium | google,bfs,dfs,good basic | AGAIN*** (3) |
| 851 | Loud and Rich | Python | O(q + r) | O(q + r) | Medium | amazon,defaultdict,good basic | AGAIN*** (3) |
| 1087 | Brace Explansion | Java | O(q + r) | O(q + r) | Medium | dfs, backtrack, good trick, google | AGAIN*** (1) |
| 1192 | Critical Connections in a Network | Python | O(q + r) | O(q + r) | Hard | Tarjan's algorithm,dfs, graph, fb, amazon | AGAIN** (1) (not start) |
| 1644 | Lowest Common Ancestor of a Binary Tree II | Java | O(q + r) | O(q + r) | Medium | LCA, LC 236, m$, fb | AGAIN (not start) |
| 1650 | Lowest Common Ancestor of a Binary Tree III | Python | O(q + r) | O(q + r) | Medium | parent node, good trick, dfs, set, dict, LCA, LC 236, amazon, google, spotify m$, fb | AGAIN******** (2) (MUST) |
| 1676 | Lowest Common Ancestor of a Binary Tree IV | Python | O(q + r) | O(q + r) | Medium | LCA, LC 236, a m$ | AGAIN (not start) |
| 3319 | K-th Largest Perfect Subtree Size in Binary Tree | Java | O(q + r) | O(q + r) | Medium | DFS, good trick, binary-tree, post order | AGAIN*** (2) |
| # | Title | Solution | Time | Space | Difficulty | Tag, Note | Status |
|---|---|---|---|---|---|---|---|
| 017 | Letter Combinations of a Phone Number | Python,Java | O(n * 4^n) | O(n) | Medium | dfs, backtrack,good trick,UBER,amazon,google,fb | AGAIN************* (11) (MUST) |
| 022 | Generate Parentheses | Python,Java | O(4^n / n^(3/2)) | O(n) | Medium | LC 20, good basic, stack, backtrac, Divide and Conquer,amazon | OK**************** (5) (but again, MUST) |
| 037 | Sudoku Solver | Python | O(4^n / n^(3/2)) | O(n) | Hard | backtrack, google, amazon, uber | AGAIN(not start) |
| 039 | Combination Sum | Python,Java | O(k * n^k) | O(k) | Medium | backtrack,dfs,good basic,UBER,airbnb,amazon,fb | OK********* (7) (but again) |
| 040 | Combination Sum II | Python,Java | O(k * C(n, k)) | O(k) | Medium | LC 39, avoud duplicated | AGAIN******* (4) (MUST) |
| 046 | Permutations | Python,Java | O(n * n!) | O(n) | Medium | backtrack, LC #77, 78,good concept,M$,linkedin,amazon,fb | OK*********** (4) (AGAIN, MUST) |
| 047 | Permutations II | Python,Java | O(n * n!) | O(n) | Medium | LC 46, avoid same layer duplicated, apple, amazon, m$ | AGAIN***** (MUST) |
| 051 | N-Queens | Java | O(n^2) | O(1) | Hard | matrix, backtrack | AGAIN |
| 052 | N-Queens II | Python,Java | O(n^2) | O(1) | Hard | matrix, backtrack | AGAIN |
| 077 | Combinations | Python,Java | O(O(k * C(n, k))) | O(k) | Medium | good trick, backtrack | OK************* (5) (but again, MUST) |
| 079 | Word Search | Python,Java | O(m * n * l) | O(l) | Medium | LC 212, Curated Top 75, back tracking,good trick,dfs,bloomberg,M$,amazon,fb | AGAIN*************** (10) (MUST) |
| 093 | Restore IP Addresses | Python | O(1) | O(1) | Medium | good trick,recursive,IP address,amazon | AGAIN****** (4) |
| 078 | Subsets | Python,Java | O(n * 2^n) | O(1) | Medium | good concept , similar as, dfs, back track,#90 Subsets II,UBER,amazon,fb | AGAIN**************** (7) (MUST again!!!) |
| 090 | Subsets II | Python,Java | O(n * 2^n) | O(1) | Medium | good basic,check# 078 Subsets, dfs, backtrack,fb | AGAIN********* (6) |
| 131 | Palindrome Partitioning | Python,Java | O(n^2) ~O(2^n) | O(n^2) | Medium | dfs, backtrack, good trick,amazon | AGAIN*********** (7) (MUST) |
| 139 | Word Break | Python,Java | O(n * l^2) | O(n) | Medium | Curated Top 75, backtracking, dfs,dp,trick,UBER,yahoo,amazon,google,fb | AGAIN**************** (7) (MUST) |
| 140 | Word Break II | Python,Java | O(n * l^2) | O(n) | Hard | good basic, LC 078, backtracking, dfs,dp,trick,amazon | AGAIN******** (2) |
| 212 | Word Search II | Python,Java | O(m * n * l) | O(l) | Hard | Curated Top 75, LC 208, LC 079, hashset, hashmap, trie, backtrack with trie,amazon, fb, apple, twitter, uber, google, indeed | AGAIN********** (3) |
| 216 | Combination Sum III | Python | O(k * C(n, k)) | O(k) | Medium | AGAIN* | |
| 254 | Factor Combinations | Python | O(nlogn) | O(logn) | Medium | 🔒 | AGAIN (not start) |
| 267 | Palindrome Permutation II | Python | O(n * n!) | O(n) | Medium | 🔒 | AGAIN (not start*) |
| 294 | Flip Game II | Python | O(n + c^2) | O(c) | Medium | 🔒, DP, Hash | AGAIN* |
| 320 | Generalized Abbreviation | Python | O(n * 2^n) | O(n) | Medium | 🔒 | AGAIN (not start*) |
| 489 | Robot Room Cleaner | Python | O(n * 2^n) | O(n) | Hard | 🔒, google, amazon, fb, m$ | AGAIN (not start) |
| 526 | Beautiful Arrangement | Python | O(n!) | O(n) | Medium | AGAIN (not start*) | |
| 676 | Implement Magic Dictionary | Python | O(n) | O(d) | Medium | Trie, DFS | AGAIN (not start) |
| 698 | Partition to K Equal Sum Subsets | Python,Java | O(n * 2^n) | O(2^n) | Medium | backtrack, DP, Memoization, similar as#416 Partition Equal Subset Sum, #473 Matchsticks to Square | AGAIN****** (2) (MUST) |
| 718 | Maximum Length of Repeated Subarray | Python | O(m * n) | O(min(m, n)) | Medium | DP, Hash, Binary Search | AGAIN (not start*) |
| 784 | Letter Case Permutation | Python | O(n * 2^n) | O(1) | Medium | dfs, recursion,good trick,fb | AGAIN****** (3) |
| 980 | Unique Paths III | Python | O(n * 2^n) | O(1) | Hard | backtrack, dfs, amazon, google,fb | AGAIN**** (1) |
| 1219 | Path with Maximum Gold | Java | O(n * 2^n) | O(1) | Medium | backtrack, dfs, bfs, google | AGAIN**** (1) |
| # | Title | Solution | Time | Space | Difficulty | Tag | Status |
|---|---|---|---|---|---|---|---|
| 53 | Maximum Subarray | Python,Java | O(n) | O(1) | Medium | MUST, Curated Top 75, brute force, Kadane algo, pre-sum array,dp basic,amazon,fb | AGAIN**************** (8) |
| 62 | Unique Paths | Python,Java | O(m * n) | O(m + n) | Medium | Curated Top 75,2D dp,basic, fb, google, apple, amazon, m$ | AGAIN**** (3) |
| 63 | Unique Paths II | Python,Java | O(m * n) | O(m + n) | Medium | trick, LC 64, dfs + dp,amazon | AGAIN* |
| 64 | Minimum Path Sum | Python,Java | O(m * n) | O(m + n) | Medium | Sum of grid values ,DP, PQ + BFS, LC 1631,amazon | AGAIN* |
| 70 | Climbing Stairs | Python,Java | O(logn) | O(1) | Easy | Curated Top 75, Matrix Exponentiation,DP,recursion,apple | OK* (2) |
| 72 | Edit Distance | Python,Java | O(logn) | O(1) | Medium | top 100 like,DP,recursion,apple, google, amazon | again (not start) |
| 91 | Decode Ways | Python,Java | O(n) | O(1) | Medium | Curated Top 75,good basic,dp,M$,UBER,amazon,fb | AGAIN************ (4) |
| 96 | Unique Binary Search Trees | Python | O(n) | O(1) | Medium | dp, Math, fb, amazon | AGAIN* (2) (not start) |
| 115 | Distinct Subsequences | Java | O(n) | O(1) | Hard | AGAIN* (1) (not start) | |
| 120 | Triangle | Python | O(m * n) | O(n) | Medium | amazon | AGAIN* (not start) (2) |
| 97 | Interleaving String | Java | O(logn) | O(1) | Medium | again (not start) | |
| 123 | Best Time to Buy and Sell Stock III | Python | O(m * n) | O(n) | Hard | amazon, uber, apple | AGAIN* (not start) (1) |
| 152 | Maximum Product Subarray | Python,Java | O(n) | O(1) | Medium | Kadane algo, dp, brute force, Curated Top 75, google, amazon, linkedin | AGAIN***** (1) |
| 198 | House Robber | Python,Java | O(n) | O(1) | Easy | Curated Top 75, dp basic,amazon | AGAIN*** (2) |
| 213 | House Robber II | Python,Java | O(n) | O(1) | Medium | brute force, recursion, dp, Curated Top 75, google, amazon | OK**** (3) (but again) |
| 221 | Maximal Square | Python,Java | O(n^2) | O(n) | Medium | EPI, dp,amazon,fb, google | AGAIN** (3) (not start) |
| 256 | Paint House | Python,Java | O(n) | O(1) | Medium | dp, google, 🔒 | AGAIN (2) |
| 276 | Paint Fence | Python | O(n) | O(1) | Easy | 🔒 | AGAIN |
| 279 | Perfect Squares | Python,Java | O(n * sqrt(n)) | O(n) | Medium | dp, bfs, brute force, GOOD trick,google | AGAIN******** (3) |
| 303 | Range Sum Query - Immutable | Python | ctor:O(n), lookup:O(1) | O(n) | Easy | OK | |
| 304 | Range Sum Query 2D - Immutable | Python,Java | ctor:O(m * n), lookup:O(1) | O(m * n) | Medium | prefix sum,dp,trick,fb | AGAIN******* (5) |
| 309 | Best Time to Buy and Sell Stock with Cooldown | Python,Java | O(n) | O(1) | Medium | AGAIN (not start) | |
| 312 | Burst Balloons | Java | O(n) | O(1) | Hard | AGAIN (not start) | |
| 322 | Coin Change | Python,Java | O(n * k) | O(k) | Medium | Curated Top 75, bfs, dfs, dp, grab, google, fb, apple,amazon | AGAIN************* (6) (MUST) |
| 329 | Longest Increasing Path in a Matrix | Java | O(n * k) | O(k) | Hard | neetcode 150, good trick, dfs, dp | AGAIN** (1) |
| 351 | Android Unlock Patterns | Python | O(9^2 * 2^9) | O(9 * 2^9) | Medium | 🔒 Backtracking, DP,google | AGAIN (not start) |
| 357 | Count Numbers with Unique Digits | Python | O(n) | O(1) | Medium | Backtracking, Math | AGAIN (not start) |
| 361 | Bomb Enemy | Python | O(m * n) | O(m * n) | Medium | 🔒 ,google | AGAIN* (2) |
| 363 | Max Sum of Rectangle No Larger Than K | Java | O(m * n) | O(m * n) | Medium | dp, pre-sum.google | AGAIN* (not start) |
| 368 | Largest Divisible Subset | Python | O(n^2) | O(n) | Medium | AGAIN (not start) | |
| 375 | Guess Number Higher or Lower II | Python | O(n^2) | O(n^2) | Medium | AGAIN (not start) | |
| 377 | Combination Sum IV | Python,Java | O(nlogn + n * t) | O(t) | Medium | Curated Top 75, AGAIN, dp basic ,fb | AGAIN******** (3) |
| 403 | Frog Jump | Python | O(nlogn + n * t) | O(t) | Hard | dfs, bfs, Memoization dfs, dp, amazon, tik-tok, m$ | AGAIN (not start) |
| 416 | Partition Equal Subset Sum | Python,Java | O(n * s) | O(s) | Medium | dp, fb, google, apple, amazon | AGAIN** (not start) (1) |
| 418 | Sentence Screen Fitting | Python | O(r + n * c) | O(n) | Medium | 🔒,dp,google | AGAIN (not start) |
| 467 | Unique Substrings in Wraparound String | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 471 | Encode String with Shortest Length | Python | O(n^3) on average | O(n^2) | Medium | 🔒,dp,google | AGAIN (not start) |
| 472 | Concatenated Words | Python | O(n * l^2) | O(n * l) | Hard | good trick,trie+dfs,dp,dfs,amazon | AGAIN******** (3) |
| 474 | Ones and Zeroes | Python | O(s * m * n) | O(m * n) | Medium | dp,google | AGAIN (not start) |
| 486 | Predict the Winner | Python | O(n^2) | O(n) | Medium | good basic,dp,google | AGAIN***** |
| 509 | Fibonacci Number | Python | O(logn) | O(1) | Easy | variant ofClimbing Stairs,Matrix Exponentiation, Spotify | OK** |
| 516 | Longest Palindromic Subsequence | Python | O(n^2) | O(n) | Medium | good DP basic,dp,UBER,amazon | AGAIN****** |
| 562 | Longest Line of Consecutive One in Matrix | Python | O(m * n) | O(n) | Medium | 🔒,dp,google | AGAIN (not start) |
| 552 | Student Attendance Record II | Java | O(m * n) | O(n) | Medium | dp,google | AGAIN (not start) |
| 576 | Out of Boundary Paths | Python | O(N * m * n) | O(m * n) | Medium | dp,bfs | AGAIN (not start) |
| 583 | Delete Operation for Two Strings | Python | O(m * n) | O(n) | Medium | dp,google | AGAIN (not start) |
| 650 | 2 Keys Keyboard | Python | O(sqrt(n)) | O(1) | Medium | dp,dp basic ,M$ | AGAIN* |
| 673 | Number of Longest Increasing Subsequence | Python | O(n^2) | O(n) | Medium | dp,good trick,fb | AGAIN********** (3) |
| 688 | Knight Probability in Chessboard | Python | O(k * n^2) | O(n^2) | Medium | dp,dp basic,AGAIN,M$,Goldman Sachs,google,fb,amazon | AGAIN********* (5) |
| 712 | Minimum ASCII Delete Sum for Two Strings | Python | O(m * n) | O(n) | Medium | dp | AGAIN (not start) |
| 714 | Best Time to Buy and Sell Stock with Transaction Fee | Python,Java | O(n) | O(1) | Medium | AGAIN,good basic,dp,greedy,fb, google | AGAIN******** (3) |
| 727 | Minimum Window Subsequence | Java | O(n) | O(1) | Hard | dp,google | AGAIN (not start) |
| 740 | Delete and Earn | Python | O(n) | O(1) | Medium | AGAIN (not start) | |
| 746 | Min Cost Climbing Stairs | Python,Java | O(n) | O(1) | Easy | good dp basic,dp,amazon | AGAIN**** (2) |
| 750 | Number Of Corner Rectangles | Python | O(n * m^2) | O(n * m) | Medium | dp,fb | AGAIN (3) (not start) |
| 764 | Largest Plus Sign | Python | O(n^2) | O(n^2) | Medium | dp, complex ,fb | AGAIN (not start) (2) |
| 788 | Rotated Digits | Python | O(logn) | O(logn) | Easy | Brute Force, Memoization | OK* |
| 790 | Domino and Tromino Tiling | Python | O(logn) | O(1) | Medium | Matrix Exponentiation,dp,google | AGAIN (not start) |
| 799 | Champagne Tower | Python | O(n^2) | O(n) | Medium | dp | AGAIN |
| 801 | Minimum Swaps To Make Sequences Increasing | Python,Java | O(n) | O(1) | Medium | dp,amazon,fb | AGAIN***** (not start) (2) |
| 808 | Soup Servings | Python | O(1) | O(1) | Medium | AGAIN (not start) | |
| 813 | Largest Sum of Averages | Python | O(k * n^2) | O(n) | Medium | dp,google | AGAIN (not start) |
| 823 | Binary Trees With Factors | Python | O(n^2) | O(n) | Medium | dp | AGAIN (not start) |
| 837 | New 21 Game | Python,Java | O(n) | O(n) | Medium | dp, trick, math,google | AGAIN (2) (not start) |
| 838 | Push Dominoes | Python | O(n) | O(n) | Medium | dp,two pointers,google | AGAIN (not start) |
| 871 | Minimum Number of Refueling Stops | Java | O(n) | O(n) | Hard | dp,heap,google | AGAIN (not start) |
| 877 | Stone Game | Python | O(n^2) | O(n) | Medium | variant ofPredict the Winner | AGAIN (not start) |
| 926 | Flip String to Monotone Increasing | Python | O(n) | O(1) | Medium | good trick, dp, prefix sum,google,amazon | AGAIN********** (4) |
| 931 | Minimum Falling Path Sum | Python | O(n^2) | O(1) | Medium | google,goldman sachs | AGAIN (not start) |
| 935 | Knight Dialer | Python | O(logn) | O(1) | Medium | Matrix Exponentiation,google,M$,fb | AGAIN (not start) |
| 518 | Coin Change 2 | Python,Java | O(logn) | O(1) | Medium | dp basic,good trick,check# 322 Coin Change,dp,google,fb | AGAIN******** (4) |
| 494 | Target Sum | Python,Java | O(logn) | O(1) | Medium | dp basic,dp,fb | AGAIN***** (1) |
| 1000 | Minimum Cost to Merge Stones | Python | O(logn) | O(1) | Medium | dp, amazon | AGAIN (not start) |
| 1048 | Longest String Chain | Java | O(logn) | O(1) | Medium | dp, google | AGAIN (not start) |
| 1049 | Last Stone Weight II | Java | O(logn) | O(1) | Medium | dp | AGAIN (not start) |
| 1137 | N-th Tribonacci Number | Java | O(logn) | O(1) | Easy | dp, good basic | AGAIN** |
| 1143 | Longest Common Subsequence | Python,Java | O(logn) | O(1) | Medium | Curated Top 75, Memoization, dp, amazon, karat | AGAIN*** (3) (not start) |
| 1312 | Minimum Insertion Steps to Make a String Palindrome | Python | O(logn) | O(1) | Hard | dp, amazon | AGAIN (not start) |
| 1335 | Minimum Difficulty of a Job Schedule | Python | O(logn) | O(1) | Medium | dp,amazon | not start |
| 1406 | Stone Game III | Java | O(logn) | O(1) | Medium | dp,amazon | AGAIN (not start) |
| 1799 | Maximize Score After N Operations | Python | O(logn) | O(1) | Medium | dp,amazon | not start |
| 3196 | Maximize Total Cost of Alternating Subarrays | Java | O(logn) | O(1) | Medium | dp, LC weekly | Again |
| # | Title | Solution | Time | Space | Difficulty | Tag, Note | Status |
|---|---|---|---|---|---|---|---|
| 011 | Container With Most Water | Python,Java | O(n) | O(1) | Medium | Curated Top 75, good basics,two pointers,fb, amazon | OK*** (3) (but again !!) |
| 045 | Jump Game II | Python,Java | O(n) | O(1) | Medium | Greedy, google, apple, fb, tesla,amazon | AGAIN******** (4) (MUST) |
| 055 | Jump Game | Python,Java | O(n) | O(1) | Medium | Curated Top 75, good trick, backtrack, Greedy, DP,amazon | AGAIN******** (8) |
| 84 | Largest Rectangle in Histogram | Python,Java | O(n) | O(1) | Hard | top 100 like, brute force, good trick,mono stack, LC 085, amazon, fb | AGAIN******** (3) |
| 122 | Best Time to Buy and Sell Stock II | Python,Java | O(n) | O(1) | Easy | compare with#309 Best Time to Buy and Sell Stock with Cooldown,#714 Best Time to Buy and Sell Stock with Transaction Fee,amazon | again* (2) |
| 134 | Gas Station | Python,Java | O(n) | O(1) | Medium | trick, greedy,amazon | AGAIN****** (5) |
| 135 | Candy | Python,Java | O(n) | O(1) | Hard | LC 123, greedy, boundary, array,amazon | AGAIN (2) |
| 218 | The Skyline Problem | Python | O(n) | O(1) | Hard | brute force, swipe line, Priority Queue, Union Find, Divide-and-Conquer, apple, microsoft | AGAIN (not start) |
| 316 | Remove Duplicate Letters | Java | O(n) | O(1) | Medium | stack, char, visited | AGAIN**** (2) |
| 330 | Patching Array | Python | O(n) | O(1) | Hard | array, greedy,amazon | AGAIN (not start) |
| 358 | Rearrange String k Distance Apart | Python | O(n) | O(1) | Medium | heap, greedy, check LC 767 | not start |
| 376 | Wiggle Subsequence | Python | O(n) | O(1) | Medium | AGAIN* | |
| 392 | Is Subsequence | Python | O(n) | O(1) | Medium | basics | OK* |
| 397 | Integer Replacement | Python | O(n) | O(1) | Medium | Recursion basics, Math | OK* |
| 402 | Remove K Digits | Python | O(n) | O(n) | Medium | LintCode | AGAIN (not start*) |
| 435 | Non-overlapping Intervals | Python,Java | O(nlogn) | O(1) | Medium | Curated Top 75, good trick, max free space, inverval, LC 452, Line Sweep,google | AGAIN************ (9) |
| 452 | Minimum Number of Arrows to Burst Balloons | Python,Java | O(nlogn) | O(1) | Medium | sort, compare i-1 element, overlap, good basic | AGAIN***** (3) |
| 455 | Assign Cookies | Python | O(nlogn) | O(1) | Easy | OK* | |
| 621 | Task Scheduler | Python,Java | O(n) | O(1) | Medium | trick,array,greedy,fb,amazon | AGAIN****** (7) |
| 646 | Maximum Length of Pair Chain | Python | O(nlogn) | O(1) | Medium | good trick, greedy, similar as#435 Non-overlapping Intervals, Line Sweep,amazon | OK********** (5) (but again) |
| 649 | Dota2 Senate | Python,Java | O(n) | O(n) | Medium | complex question | AGAIN (not start*) |
| 659 | Split Array into Consecutive Subsequences | Python,Java | O(n) | O(1) | Medium | map, pq, greedy, dp,google | AGAIN***** (1) |
| 738 | Monotone Increasing Digits | Python | O(1) | O(1) | Medium | good trick, greedy, string, trick,Amazon | AGAIN********* (4) |
| 763 | Partition Labels | Python,Java | O(n) | O(S) | Medium | greedy,good trick ,dict,sliding window,amazon | AGAIN******* (6) (AGAIN) |
| 767 | Reorganize String | Python,Java | O(n) | O(1) | Medium | PQ, hashmap,good trick,amazon,fb, google | AGAIN****************** (9) (MUST) |
| 861 | Score After Flipping Matrix | Python | O(r * c) | O(1) | Medium | AGAIN (not start*) | |
| 870 | Advantage Shuffle | Python | O(nlogn) | O(n) | Medium | OK* | |
| 881 | Boats to Save People | Python,Java | O(nlogn) | O(n) | Medium | good trick | AGAIN* (2) |
| 948 | Bag of Tokens | Python | O(nlogn) | O(1) | Medium | Two Pointers | AGAIN (not start) |
| 962 | Maximum Width Ramp | Python | O(n) | O(n) | Medium | Descending Stack | AGAIN (not start) |
| 978 | Longest Turbulent Subarray | Java | O(n) | O(n) | Medium | sliding window | AGAIN (not start) |
| 1024 | Video Stitching | Python | Medium | Spotify | AGAIN (not start) | ||
| 1102 | Path With Maximum Minimum Value | Python | Medium | dfs, dp , greedy,amazon | not start | ||
| 319 | Bulb Switcher | Python | Medium | not start | |||
| 672 | Bulb Switcher II | Python | Medium | not start | |||
| 1375 | Bulb Switcher III | Python | Medium | queue, array,gra* | AGAIN*** (1) | ||
| 1648 | Sell Diminishing-Valued Colored Balls | Python | Medium | trick, sorting, heapq, binary search, greedy,amazon | AGAIN*** (2) (not start) | ||
| 1710 | Maximum Units on a Truck | Python | Easy | sort, greedy,amazon | AGAIN******** (3) (MUST) | ||
| 1851 | Minimum Interval to Include Each Query | Java | Hard | sort, greedy,google | AGAIN (not start) | ||
| 1871 | Jump Game VII | Java | Medium | greedy, bfs | AGAIN (not start) | ||
| 1899 | Merge Triplets to Form Target Triplet | Java | Medium | sort, greedy,amazon | AGAIN(1) (not srart) | ||
| 3689 | Maximum Total Subarray Value I | Java | Medium | math, brute force | OK | ||
| 3690 | Split and Merge Array Transformation | Java | Medium | bfs dfs | AGAIN (not start) | ||
| 3691 | Maximum Total Subarray Value II | Java | hard | brute force, tree | AGAIN |
| # | Title | Solution | Time | Space | Difficulty | Status | Note |
|---|---|---|---|---|---|---|---|
| 269 | Alien Dictionary | Python,Java | Hard | Curated Top 75, good trick, dfs, bfs, Topologicals sort,fb, google, m$, airbnb, uber, amazon | AGAIN********** (6) | ||
| 323 | Number of Connected Components in an Undirected Graph | Python,Java | O(n) | O(n) | Medium | Curated Top 75, LC 547, 🔒 , bfs, dfs, Union Find,graph,linkedin,amazon, fb, google, m$, linkedin | AGAIN************** (6) (MUST) |
| 778 | Swim in Rising Water | Java | O(n) | O(n) | Medium | graph, Dijkstra | AGAIN1 (1) (not start) |
| 959 | Regions Cut By Slashes | Python | O(n^2) | O(n^2) | Medium | Union Find | again |
| 997 | Find the Town Judge | Java | O(n^2) | O(n^2) | Easy | graph | again |
| 1135 | Connecting Cities With Minimum Cost | Python | O(n^2) | O(n^2) | Medium | union find, Kruskal, prime, graph, amazon | AGAIN (not start) |
| 1462 | Course Schedule IV | Java | O(n^2) | O(n^2) | Medium | AGAIN (not start) | |
| 1489 | Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree | Java | O(n^2) | O(n^2) | Hard | dfs, bfs, Dijkstra | AGAIN (not start) |
| 1584 | Min Cost to Connect All Points | Java | O(n^2) | O(n^2) | Medium | Kruskal algo, Prim algo, advanced graph | AGAIN (not start) |
| 1631 | Path With Minimum Effort | Java | O(n^2) | O(n^2) | Hard | Max of step differences, dfs, bfs+PQ, LC 64, Dijkstra | AGAIN**** (1) |
| 2290 | Minimum Obstacle Removal to Reach Corner | Java | O(n^2) | O(n^2) | Hard | bfs, PQ, Dijkstra classics | AGAIN****** (2)(MUST) |
| 2392 | Build a Matrix With Conditions | Java | O(n^2) | O(n^2) | Hard | dfs, bfs, Dijkstra | AGAIN (not start) |
| 2508 | Add Edges to Make Degrees of All Nodes Even | Java | O(n^2) | O(n^2) | Hard | graph, LC weekly | AGAIN (not start) |
| 2709 | Greatest Common Divisor Traversal | Java | O(n^2) | O(n^2) | Hard | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Status | Note |
|---|---|---|---|---|---|---|---|
| 892 | Surface Area of 3D Shapes | C++Python | O(n^2) | O(1) | Easy | ||
| 0587 | Erect the Fence | Python | O(nlogn) | O(n) | Hard | complex, Convex Hull,Monotone Chain ,amazon | |
| 0892 | Surface Area of 3D Shapes |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 146 | LRU Cache | Python,Java | O(1) | O(k) | Medium | good basic, LRU, Least Recently Used, Double Linkedlist, LinkedHashMap, OrderedDict, priority queue,amazon | AGAIN****** (4) |
| 225 | Implement Stack using Queues | Python,Java | push:O(n), pop:O(1), top:O(1) | O(n) | Easy | AGAIN** (1)(MUST) | |
| 284 | Peeking Iterator | C++Python | O(1) | O(1) | Medium | good basic,google, apple | not start*** (1) |
| 348 | Design Tic-Tac-Toe | Python | O(1) | O(n^2) | Medium | matrix, array, 🔒, google,fb,amazon | AGAIN****** (5) |
| 353 | Design Snake Game | Python,Java | O(1) | O(s) | Medium | good trick, Deque, 🔒, amazon, google, square, m$ | AGAIN*** (1) |
| 355 | Design Twitter | Python,Java | O(klogu) | O(t + f) | Medium | good trick, data structure, heapq, defaultdict,amazon | OK******** (6) |
| 362 | Design Hit Counter | Java | O(1), amortized | O(k) | Medium | 🔒 | Deque,google |
| 379 | Design Phone Directory | Java | O(1) | O(n) | Medium | 🔒, queue, google | |
| 380 | Insert Delete GetRandom O(1) | Python,Java | O(1) | O(n) | Medium/Hard | set, list, dict,amazon,fb, google | OK* (5) |
| 0381 | Insert Delete GetRandom O(1) - Duplicates allowed | C++Python | O(1) | O(n) | Hard | ||
| 432 | All O`one Data Structure | C++Python | O(1) | O(n) | Hard | ||
| 460 | LFU Cache | Python,Java | O(1) | O(k) | Hard | Least Frequently Used (LFU) cache, complex,amazon | AGAIN*** (3) |
| 535 | Encode and Decode TinyURL | Python,Java | O(1) | O(n) | Medium | hash map, "duplicated", "hash map collision" ,UBER,amazon,google ,fb, design | OK**** (5) |
| 588 | Design In-Memory File System | C++Python | ls:O(l + klogk) mkdir:O(l) addContentToFile:O(l + c) readContentFromFile:O(l + c) | O(n + s) | Hard | dict, a bit complex basic, 🔒, shoptify, amazon | AGAIN******* (3) |
| 0604 | Design Compressed String Iterator | C++Python | O(1) | O(1) | Easy | 🔒 | |
| 622 | Design Circular qeque | Python | Medium | 🔒 | AGAIN(2) | ||
| 631 | Design Excel Sum Formula | C++Python | set:O((r * c)^2) get:O(1) sum:O((r * c)^2) | O(r * c) | Hard | 🔒 | |
| 635 | Design Log Storage System | C++Python | put:O(1) retrieve:O(n + dlogd) | O(n) | Medium | 🔒 | |
| 641 | Design Circular Deque | Python | Medium | 🔒 | |||
| 642 | Design Search Autocomplete System | Python | O(p^2) | O(p * t + s) | Hard | 🔒,amazon | AGAIN**** (not start) (5) |
| 705 | Design HashSet | Python | Easy | ||||
| 706 | Design HashMap | Python | Easy | ||||
| 0715 | Range Module | C++Python | add:O(n) remove:O(n) query:O(logn) | O(n) | Hard | ||
| 716 | Max Stack | Python | push:O(logn) pop:O(logn) popMax:O(logn) top:O(1) peekMax:O(1) | O(n) | Easy | basic, stack,amazon | again* |
| 745 | Prefix and Suffix Search | Python | ctor:O(w * l^2) search :O(p + s) | O(t) | Hard | Trie,fb | Not start* (1) (good basic) |
| 900 | RLE Iterator | C++Python,Java | O(n) | O(1) | Medium | google, treemap, array | AGAIN (not start) (1) |
| 1146 | Snapshot Array | Java | set:O(1) get:O(logn) | O(n) | Medium | treeMap, binary search, google | AGAIN*** (1) |
| 1166 | Design File System | C++Python | create:O(n) get:O(n) | O(n) | Medium | 🔒, design, google, airbnb, amazon | AGAIN***** (1) |
| 1172 | Dinner Plate Stacks | C++Python | push:O(logn) pop:O(1), amortized popAtStack:(logn) | O(n * c) | Hard | ||
| 1188 | Design Bounded Blocking Queue | Java | push:O(logn) pop:O(1), amortized popAtStack:(logn) | O(n * c) | Medium | google, Semaphore | AGAIN (not start) |
| 1206 | Design Skiplist | C++Python | O(logn), on average | O(n) | Hard | ||
| 1236 | Web Crawler | C++Python | O(|V| + |E|) | O(|V|) | Medium | 🔒, BFS, DFS | |
| 1244 | Design A Leaderboard | C++Python | ctor:O(1) add:O(1) top:O(n) reset:O(1) | O(n) | Medium | ||
| 1268 | Search Suggestions System | Python,Java | ctor:O(n * l) suggest:O(l^2) | O(t) | Medium | good basic, array, heap, sort, Trie,amazon | AGAIN******** (3) |
| 1286 | Iterator for Combination | Python | O(k) | O(k) | Medium | Stack | |
| 1429 | First Unique Number | Python | O(k) | O(k) | Medium | good trick, heap,amazon | AGAIN*** (not start) |
| 1472 | Design Browser History | Python | O(k) | O(k) | Medium | AGAIN | |
| 1500 | Design a File Sharing System | Python | O(k) | O(k) | Medium | design, hashmap | AGAIN*** (not start) |
| 1603 | Design Parking System | Python | O(k) | O(k) | Easy | design, amazon , paypal | OK |
| 1628 | Design an Expression Tree With Evaluate Function | Python | O(k) | O(k) | Medium | complex, design,amazon | AGAIN*** (not start) |
| 1656 | Design an Ordered Stream | Python | O(k) | O(k) | Easy | ||
| 1670 | Design Front Middle Back Queue | Python | O(k) | O(k) | Medium | good basic, Design,amazon | AGAIN** (1) (not start) |
| 1756 | Design Recent Used Queue | Python | O(k) | O(k) | Medium | design, queue | AGAIN |
| 1797 | Design Authentication Manager | Python | O(k) | O(k) | Medium | design, hashmap | AGAIN |
| 1976 | Number of Ways to Arrive at Destination | Python | O(k) | O(k) | Medium |
| # | Title | Solution | Time | Space | Difficulty | Status | Note |
|---|---|---|---|---|---|---|---|
| 874 | Walking Robot Simulation | C++Python | O(n + k) | O(k) | Easy |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 1114 | Print in Order | C++Python | O(n) | O(1) | Easy | ||
| 1115 | Print FooBar Alternately | C++Python | O(n) | O(1) | Medium | ||
| 1116 | Print Zero Even Odd | C++Python | O(n) | O(1) | Medium | ||
| 1117 | Building H2O | C++Python | O(n) | O(1) | Hard | ||
| 1188 | Design Bounded Blocking Queue | C++Python | O(n) | O(1) | Medium | 🔒 | |
| 1195 | Fizz Buzz Multithreaded | C++Python | O(n) | O(1) | Medium | ||
| 1226 | The Dining Philosophers | C++Python | O(n) | O(1) | Medium | ||
| 1242 | Web Crawler Multithreaded | C++Python | O(|V| + |E|) | O(|V|) | Medium | 🔒 | |
| 1279 | Traffic Light Controlled Intersection | C++Python | O(n) | O(1) | Easy | 🔒 |
| # | Title | Solution | Time | Space | Difficulty | Tag, Note | Status |
|---|---|---|---|---|---|---|---|
| 0175 | Combine Two Tables | MySQL | O(m + n) | O(m + n) | Easy | OK (4) | |
| 0176 | Second Highest Salary | MySQL | O(n) | O(1) | Easy | amazon,fb | OK (4) |
| 0177 | Nth Highest Salary | MySQL | O(n^2) | O(n) | Medium | MySQL PROCEDURE,SQL FAQ | AGAIN*** (3) |
| 0178 | Rank Scores | MySQL | O(n^2) | O(n) | Medium | trick,SQL var, ank, select same table, rank | AGAIN****** (7) |
| 0180 | Consecutive Numbers | MySQL | O(n) | O(n) | Medium | SQL var, join same table multi times | OK* (3) |
| 0181 | Employees Earning More Than Their Managers | MySQL | O(n^2) | O(1) | Easy | OK | |
| 0182 | Duplicate Emails | MySQL | O(n^2) | O(n) | Easy | OK | |
| 0183 | Customers Who Never Order | MySQL | O(n^2) | O(1) | Easy | left join | OK** (3) (but again) |
| 0184 | Department Highest Salary | MySQL | O(n^2) | O(n) | Medium | trick, where, good basic | OK***** (but again) (6) |
| 0185 | Department Top Three Salaries | MySQL | O(n^2) | O(n) | Hard | similiar as# 0177 Nth Highest Salary, good trick, top N in group | AGAIN******** (5) |
| 0196 | Delete Duplicate Emails | MySQL | O(n^2) | O(n) | Easy, delete command | AGAIN (2) | |
| 0197 | Rising Temperature | MySQL | O(n^2) | O(n) | Easy | OK | |
| 0262 | Trips and Users | MySQL | O((t * u) + tlogt) | O(t) | Hard | case condisions | OK* (2) |
| 0511 | Game Play Analysis I | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 0512 | Game Play Analysis II | MySQL | O(n) | O(n) | Easy | 🔒,2 col wheregood trick | AGAIN**(4) |
| 0534 | Game Play Analysis III | MySQL | O(nlogn) | O(n) | Medium | 🔒,SQL var,tricky, window func | AGAIN******** (6) |
| 0550 | Game Play Analysis IV | MySQL | O(n) | O(n) | Medium | case, fraction, join, good basic, where min condition | OK*********** (7) (but again) |
| 569 | Median Employee Salary | MySQL | O(n) | O(n) | Medium | medium number | AGAIN* (not start) |
| 571 | Find Median Given Frequency of Numbers | MySQL | O(n) | O(n) | Medium | medium number | AGAIN** (not start) (2) |
| 577 | Employee Bonus | MySQL | O(n) | O(n) | Easy | OK | |
| 578 | Get Highest Answer Rate Question | MySQL | Medium | fb, case condition | OK* (3) | ||
| 579 | Find Cumulative Salary of an Employee | MySQL | Hard | window function,amazon, good trick | OK***** (5)(but again) | ||
| 580 | Count Student Number in Departments | MySQL | Medium | OK*** (2) (but again) | |||
| 595 | Big Countries | MySQL | Easy | OK | |||
| 597 | Friend Requests I: Overall Acceptance Rate | MySQL | Medium | select distinct, ifnull,fb | OK*** (7) | ||
| 601 | Human Traffic of Stadium | MySQL | Hard | consecutive nums | OK* (1) | ||
| 602 | Friend Requests II: Who Has Most Friend? | MySQL | Medium | union all,fb | OK*** (4) | ||
| 603 | Consecutive Available Seats | MySQL | Medium | consecutive nums, good basic, cross join | OK***** (3)(but again) | ||
| 618 | Students Report By Geography | MySQL | Hard | sql var | AGAIN (not start) | ||
| 620 | Not Boring Movies | MySQL | Easy | OK | |||
| 626 | Exchange Seats | MySQL | Medium | AGAIN (not start) | |||
| 627 | Swap Salary | MySQL | Easy | UPDATE with CASE, good basic | OK* (1) (but again) | ||
| 1045 | Customers Who Bought All Products | MySQL | O(n + k) | O(n + k) | Medium | 🔒, where with count | OK*** (4) |
| 1050 | Actors and Directors Who Cooperated At Least Three Times | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1068 | Product Sales Analysis I | MySQL | O(m + n) | O(m + n) | Easy | 🔒 | OK |
| 1069 | Product Sales Analysis II | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1070 | Product Sales Analysis III | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1075 | Project Employees I | MySQL | O(m + n) | O(m + n) | Easy | 🔒 | OK |
| 1076 | Project Employees II | MySQL | O(n) | O(n) | Easy | 🔒 | OK (2) |
| 1077 | Project Employees III | MySQL | O((m + n)^2) | O(m + n) | Medium | 🔒,tricky where | OK***** (2) (but again) |
| 1082 | Sales Analysis I | MySQL | O(n) | O(n) | Easy | 🔒, group by only 1 col, good basic | OK***** (5) (again) |
| 1083 | Sales Analysis II | MySQL | O(m + n) | O(m + n) | Easy | 🔒, not in | OK*** (3) (again) |
| 1084 | Sales Analysis III | MySQL | O(m + n) | O(m + n) | Easy | 🔒 | OK** (2) |
| 1097 | Game Play Analysis V | MySQL | O(n^2) | O(n) | Hard | 🔒,good basic,retention, case condition, retention, data_add, left join | AGAIN******* (8) |
| 1098 | Unpopular Books | MySQL | O(m + n) | O(n) | Medium | 🔒, where not in | OK* (2) |
| 1107 | New Users Daily Count | MySQL | O(n) | O(n) | Medium | 🔒 | OK* |
| 1112 | Highest Grade For Each Student | MySQL | O(nlogn) | O(n) | Medium | 🔒, good basic | OK** (4) |
| 1113 | Reported Posts | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1126 | Active Businesses | MySQL | O(n) | O(n) | Medium | 🔒,good basic | AGAIN*** (3) |
| 1127 | User Purchase Platform | MySQL | O(n) | O(n) | Hard | 🔒,complex, union all, case | OK**** (6) (but again) |
| 1132 | Reported Posts II | MySQL | O(m + n) | O(n) | Medium | 🔒 | OK*** (4) |
| 1141 | User Activity for the Past 30 Days I | MySQL | O(n) | O(n) | Easy | 🔒 | AGAIN* (2) |
| 1142 | User Activity for the Past 30 Days II | MySQL | O(n) | O(n) | Easy | 🔒 | AGAIN* (1) |
| 1148 | Article Views I | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK |
| 1149 | Article Views II | MySQL | O(nlogn) | O(n) | Medium | 🔒 | OK* |
| 1158 | Market Analysis I | MySQL | O(m + n) | O(m + n) | Medium | 🔒,case when ... is not null | AGAIN**** (5) |
| 1159 | Market Analysis II | MySQL | O(m + n) | O(m + n) | Hard | 🔒, good trick | AGAIN** (3) |
| 1164 | Product Price at a Given Date | MySQL | O(mlogn) | O(m) | Medium | 🔒, good trick, union, case, not in a period | AGAIN******** (2) |
| 1173 | Immediate Food Delivery I | MySQL | O(n) | O(1) | Easy | 🔒 | OK |
| 1174 | Immediate Food Delivery II | MySQL | O(n) | O(m) | Medium | 🔒 | OK**** (3) |
| 1179 | Reformat Department Table | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1193 | Monthly Transactions I | MySQL | O(n) | O(n) | Medium | 🔒 | OK (2) |
| 1194 | Tournament Winners | MySQL | O(m + n + nlogn) | O(m + n) | Hard | 🔒 | AGAIN* |
| 1204 | Last Person to Fit in the Elevator | MySQL | O(nlogn) | O(n) | Medium | 🔒, cumsum, window func, good basic | OK****** (3) |
| 1205 | Monthly Transactions II | MySQL | O(n) | O(n) | Medium | 🔒, good trick, union all, case conditions | OK*** (3) (but again) |
| 1211 | Queries Quality and Percentage | MySQL | O(n) | O(n) | Easy | OK | |
| 1212 | Team Scores in Football Tournament | MySQL | O(nlogn) | O(n) | Medium | good trick | OK** (2) |
| 1225 | Report Contiguous Dates | MySQL | O(nlogn) | O(n) | Hard | 🔒 | AGAIN* (2) (not start) |
| 1241 | Number of Comments per Post | MySQL | O(n) | O(n) | Easy | 🔒, good basic | OK**** (5) (but again) |
| 1251 | Average Selling Price | MySQL | O(n) | O(n) | Easy | 🔒, good basic | OK*** (but again) (3) |
| 1264 | Page Recommendations | MySQL | O(m + n) | O(m) | Medium | 🔒 | OK** (2) |
| 1270 | All People Report to the Given Manager | MySQL | O(n) | O(n) | Medium | 🔒, good basic | OK* (3) |
| 1280 | Students and Examinations | MySQL | O((m * n) * log(m * n)) | O(m * n) | Easy | 🔒 | OK (1) |
| 1285 | Find the Start and End Number of Continuous Ranges | MySQL | O(n) | O(n) | Medium | 🔒, variable | AGAIN (not start) (1) |
| 1294 | Weather Type in Each Country | MySQL | O(m + n) | O(n) | Easy | 🔒 | OK (1) |
| 1303 | Find the Team Size | MySQL | O(n) | O(n) | Easy | 🔒 | ok (1) |
| 1308 | Running Total for Different Genders | MySQL | O(nlogn) | O(n) | Medium | 🔒, good basic, union all, window func | OK**** (3) |
| 1321 | Restaurant Growth | MySQL | O(n^2) | O(n) | Medium | 🔒, good basic, trick | AGAIN***** (3) |
| 1322 | Ads Performance | MySQL | O(nlogn) | O(n) | Easy | 🔒, good basic | OK******* (3) (but again) |
| 1327 | List the Products Ordered in a Period | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1336 | Number of Transactions per Visit | MySQL | O(m + n) | O(m + n) | Medium | 🔒, complex, variable | AGAIN (not start) |
| 1341 | Movie Rating | MySQL | O(nlogn) | O(n) | Medium | 🔒 | AGAIN (not start) |
| 1350 | Students With Invalid Departments | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1355 | Activity Participants | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1364 | Number of Trusted Contacts of a Customer | MySQL | O(n + m + l + nlogn) | O(n + m + l) | Medium | 🔒 | OK |
| 1369 | Get the Second Most Recent Activity | MySQL | O(nlogn) | O(n) | Hard | 🔒, union, having | OK** (2) (but again) |
| 1378 | Replace Employee ID With The Unique Identifier | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1384 | Total Sales Amount by Year | MySQL | O(nlogn) | O(n) | Hard | 🔒, complex | OK* |
| 1393 | Capital Gain/Loss | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1398 | Customers Who Bought Products A and B but Not C | MySQL | O(m + n) | O(m + n) | Medium | 🔒 | OK |
| 1407 | Top Travellers | MySQL | O(m + nlogn) | O(m + n) | Easy | 🔒, ifnull | OK* |
| 1412 | Find the Quiet Students in All Exams | MySQL | O(m + nlogn) | O(m + n) | Hard | 🔒, good trick, not in, inner join on multiple cols | OK**** (3) (but again) |
| 1421 | NPV Queries | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1435 | Create a Session Bar Chart | MySQL | O(n) | O(1) | Easy | 🔒 | OK |
| 1440 | Evaluate Boolean Expression | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1445 | Apples & Oranges | MySQL | O(n) | O(n) | Medium | 🔒 | OK |
| 1454 | Active Users | MySQL | O(nlogn) | O(n) | Medium | 🔒, good basic, window func | AGAIN*** (2) |
| 1459 | Rectangles Area | MySQL | O(n^2) | O(n^2) | Medium | 🔒 | OK* |
| 1468 | Calculate Salaries | MySQL | O(m + n) | O(m + n) | Easy | 🔒 | OK* |
| 1479 | Sales by Day of the Week | MySQL | O(m + n) | O(n) | Hard | 🔒, case, DAYOFWEEK | OK |
| 1484 | Group Sold Products By The Date | MySQL | O(nlogn) | O(n) | Easy | 🔒,GROUP_CONCAT | OK* |
| 1495 | Friendly Movies Streamed Last Month | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1501 | Countries You Can Safely Invest In | MySQL | O(n) | O(n) | Medium | 🔒,good trick, group avg, global avg, SUBSTRING, inner join onor conditions | OK****** (4) |
| 1511 | Customer Order Frequency | MySQL | O(n) | O(n) | Easy | 🔒, having, like | OK* (1) |
| 1517 | Find Users With Valid E-Mails | MySQL | O(n) | O(n) | Easy | 🔒, regular expression | AGAIN |
| 1527 | Patients With a Condition | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1532 | The Most Recent Three Orders | MySQL | O(nlogn) | O(n) | Medium | 🔒, window func, good basic | OK** (2) (but again) |
| 1543 | Fix Product Name Format | MySQL | O(nlogn) | O(n) | Easy | 🔒, trim | OK |
| 1549 | The Most Recent Orders for Each Product | MySQL | O(nlogn) | O(n) | Medium | 🔒, max day per id, good basic | OK* (again) |
| 1555 | Bank Account Summary | MySQL | O(m + n) | O(m + n) | Medium | 🔒, union all, good trick | OK**** (2)(but again) |
| 1565 | Unique Orders and Customers Per Month | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1571 | Warehouse Manager | MySQL | O(n) | O(n) | Medium | 🔒 | OK* (1) |
| 1581 | Customer Who Visited but Did Not Make Any Transactions | MySQL | O(n) | O(n) | Easy | 🔒, left join, good basic | OK** (2)(but again) |
| 1587 | Bank Account Summary II | MySQL | O(m + n) | O(m + n) | Easy | 🔒 | OK |
| 1596 | The Most Frequently Ordered Products for Each Customer | MySQL | O(n) | O(n) | Medium | 🔒, good trick,rank() ORDER BY count, get max in each group | OK********* (3)(but again) |
| 1607 | Sellers With No Sales | MySQL | O(nlogm) | O(n + m) | Medium | 🔒 | OK |
| 1613 | Find the Missing IDs | MySQL | O(n^2) | O(n) | Medium | 🔒,RECURSIVE CTE, good trick | AGAIN*** (2) |
| 1623 | All Valid Triplets That Can Represent a Country | MySQL | O(n^3) | O(n^3) | Easy | 🔒,<> | AGAIN* (not start) |
| 1633 | Percentage of Users Attended a Contest | MySQL | O(m + nlogn) | O(n) | Easy | 🔒 | OK |
| 1635 | Hopper Company Queries I | MySQL | O(d + r + tlogt) | O(d + r + t) | Hard | 🔒, complex | AGAIN (not start) |
| 1645 | Hopper Company Queries II | MySQL | O(d + r + tlogt) | O(d + r + t) | Hard | 🔒, complex | AGAIN (not start) |
| 1651 | Hopper Company Queries III | MySQL | O(d + r + tlogt) | O(d + r + t) | Hard | 🔒, complex | AGAIN (not start) |
| 1661 | Average Time of Process per Machine | MySQL | O(n) | O(n) | Easy | 🔒, good basic | OK* (1) |
| 1667 | Fix Names in a Table | MySQL | O(nlogn) | O(n) | Easy | 🔒, concat, sub-string | OK (1) |
| 1677 | Product's Worth Over Invoices | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK |
| 1683 | Invalid Tweets | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1693 | Daily Leads and Partners | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1699 | Number of Calls Between Two Persons | MySQL | O(n) | O(n) | Medium | 🔒, cte, union all | OK* (1)(but again) |
| 1709 | Biggest Window Between Visits | MySQL | O(nlogn) | O(n) | Medium | 🔒, window func, datediff, coalesce, good trick | AGAIN***** (2) |
| 1715 | Count Apples and Oranges | MySQL | O(n) | O(n) | Medium | 🔒, ifnull | OK (2) |
| 1729 | Find Followers Count | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK |
| 1731 | The Number of Employees Which Report to Each Employee | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK |
| 1741 | Find Total Time Spent by Each Employee | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK |
| 1747 | Leetflex Banned Accounts | MySQL | O(n^2) | O(n) | Medium | 🔒 | OK (2) (but again) |
| 1757 | Recyclable and Low Fat Products | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1767 | Find the Subtasks That Did Not Execute | MySQL | O(n * c) | O(n * c) | Hard | 🔒,RECURSIVE CTE | AGAIN (not start) |
| 1777 | Product's Price for Each Store | MySQL | O(n) | O(n) | Easy | 🔒 | OK (2) |
| 1783 | Grand Slam Titles | MySQL | O(n) | O(n) | Medium | 🔒, union all, good basic | OK* (1) (but again) |
| 1789 | Primary Department for Each Employee | MySQL | O(n) | O(n) | Easy | 🔒, where id in | OK (1) (but again) |
| 1795 | Rearrange Products Table | MySQL | O(n) | O(n) | Easy | 🔒, union all, good basic | OK****** (2) |
| 1809 | Ad-Free Sessions | MySQL | O(n) | O(n) | Easy | 🔒, left join where col is null | OK**** (3)(but again) |
| 1811 | Find Interview Candidates | MySQL | O(nlogn) | O(n) | Medium | 🔒, union all, cte, where,good basic | AGAIN* (2) |
| 1821 | Find Customers With Positive Revenue this Year | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1831 | Maximum Transaction Each Day | MySQL | O(nlogn) | O(n) | Medium | 🔒, rank(), where on 2 attr, good basic | AGAIN**** (2) |
| 1841 | League Statistics | MySQL | O(nlogn) | O(n) | Medium | 🔒, case, complex | AGAIN* (2) |
| 1843 | Suspicious Bank Accounts | MySQL | O(nlogn) | O(n) | Medium | 🔒, good trick, window func | OK** (2) (but AGAIN) |
| 1853 | Convert Date Format | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1867 | Orders With Maximum Quantity Above Average | MySQL | O(n) | O(n) | Easy | 🔒 | OK (1) |
| 1873 | Calculate Special Bonus | MySQL | O(n) | O(n) | Easy | 🔒, left, odd num | OK (2) |
| 1875 | Group Employees of the Same Salary | MySQL | O(nlogn) | O(n) | Medium | 🔒, complex, good basic | AGAIN* (1) |
| 1890 | The Latest Login in 2020 | MySQL | O(n) | O(n) | Easy | 🔒 | OK |
| 1892 | Page Recommendations II | MySQL | O(n * m) | O(n * m) Hard | 🔒 | AGAIN*** (1) (not start) | |
| 1907 | Count Salary Categories | MySQL | O(n) | O(n) | Medium | 🔒, union all | OK* (1) |
| 1917 | Leetcodify Friends Recommendations | MySQL | O(n^2) | O(n^2) | Hard | 🔒,NOT EXISTS | AGAIN*** (2) |
| 1919 | Leetcodify Similar Friends | MySQL | O(n * l) | O(n * l) | Hard | 🔒 | AGAIN* (not start) |
| 1934 | Confirmation Rate | MySQL | O(n + m) | O(n + m) | Medium | 🔒, good basic | OK* (1) (but again) |
| 1939 | Users That Actively Request Confirmation Messages | MySQL | O(nlogn) | O(n) | Easy | 🔒, TIMESTAMPDIFF, good basic | OK*** (2) (but again) |
| 1949 | Strong Friendship | MySQL | O(n^3) | O(n^2) | Medium | 🔒 | good basic, where in 2 cols |
| 1951 | All the Pairs With the Maximum Number of Common Followers | MySQL | O(n^3) | O(n^2) | Medium | 🔒, good trick | AGAIN* (2) |
| 1965 | Employees With Missing Information | MySQL | O(nlogn) | O(n) | Easy | 🔒, good basic | OK* (1) (but again) |
| 1972 | First and Last Call On the Same Day | MySQL | O(n) | O(n) | Hard | 🔒, rank, union all, amazon | AGAIN** (2) |
| 1978 | Employees Whose Manager Left the Company | MySQL | O(nlogn) | O(n) | Easy | 🔒 | OK (1) |
| 1988 | Find Cutoff Score for Each School | MySQL | O(n * m) | O(n * m) | Medium | 🔒, no ref | AGAIN (not start) |
| 1990 | Count the Number of Experiments | MySQL | O(n) | O(n) | Easy | 🔒, cross join | AGAIN* (1) |
| 2004 | The Number of Seniors and Juniors to Join the Company | MySQL | O(nlogn) | O(n) | Hard | 🔒, not ref | AGAIN (not start) |
| # | Title | Solution | Time | Space | Difficulty | Tag | Note |
|---|---|---|---|---|---|---|---|
| 0192 | Word Frequency | Shell | O(n) | O(k) | Medium | ||
| 0193 | Valid Phone Numbers | Shell | O(n) | O(1) | Easy | ||
| 0194 | Transpose File | Shell | O(n^2) | O(n^2) | Medium | ||
| 0195 | Tenth Line | Shell | O(n) | O(1) | Easy |
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