| 415 | Add Strings | Solution | O(n) | O(1) | Easy | | |
| 350 | Intersection of Two Arrays II | Solution | O(m+n) | O((m+n)) could be optimized | Easy | HashMap, Binary Search | |
| 349 | Intersection of Two Arrays | Solution | O(m+n) | O(min(m,n)) | Easy | Two Pointers, Binary Search | |
| 325 | Maximum Size Subarray Sum Equals k | [Solution] | O(n) | O(n) | Medium | HashMap | |
| 314 | Binary Tree Vertical Order Traversal | Solution | O(n) | O(n) | Medium | HashMap, BFS | |
| 301 | Remove Invalid Parentheses | [Solution] | ? | ? | Hard | BFS | |
| 283 | Move Zeroes | Solution | O(n) | O(1) | Easy | | |
| 278 | First Bad Version | Solution | O(logn) | O(1) | Easy | Binary Search | |
| 273 | Integer to English Words | [Solution] | | | | | |
| 257 | Binary Tree Paths | Solution | O(n*h) | O(h) | DFS/Recursion | | |
| 209 | Minimum Size Subarray Sum | Solution | O(n) | O(1) | Medium | | |
| 206 | Reverse Linked List | Solution | O(n) | O(1) | Easy | | |
| 200 | Number of Islands | Union FindDFS | O(m*n) | O(m*n) | Medium | Union Find, DFS | |
| 173 | Binary Search Tree Iterator | QueueStack | O(1) | O(h) | Medium | | |
| 140 | Word Break II | Solution | ? | O(n^2) | Hard | Backtracking/DFS | |
| 139 | Word Break | Solution | O(n^2) | O(n) | Medium | DP | |
| 133 | Clone Graph | Solution | O(n) | O(n) | Medium | HashMap, BFS | |
| 125 | Valid Palindrome | Solution | O(n) | O(1) | Easy | Two Pointers | |
| 122 | Best Time to Buy and Sell Stock II | Solution | O(n) | O(1) | Medium | Greedy | |
| 121 | Best Time to Buy and Sell Stock | Solution | O(n) | O(1) | Easy | DP | |
| 117 | Populating Next Right Pointers in Each Node II | Solution | O(n) | O(1) | Hard | BFS | |
| 116 | Populating Next Right Pointers in Each Node | Solution | O(n) | O(1) | Medium | BFS | |
| 91 | Decode Ways | Solution | O(n) | O(n) | Medium | DP | |
| 98 | Validate Binary Search Tree | [Solution] | O(n) | O(1) | Medium | DFS/Recursion | |
| 79 | Word Search | Solution | O(mnl) ? | O(m*n) | Medium | Backtracking/DFS | |
| 78 | Subsets | Solution | O(n^2) ? | O(1) | Medium | Backtracking | |
| 76 | Minimum Window Substring | Solution | O(n) | O(k) | Hard | Two Pointers | |
| 75 | Sort Colors | [Solution] | O(n) | O(1) | Medium | | |
| 67 | Add Binary | Solution | O(n) | O(1) | Easy | | |
| 56 | Merge Intervals | Solution | O(n*logn) | O(1) | Hard | | |
| 43 | Multiply Strings | [Solution] | | | Medium | | |
| 23 | Merge k Sorted Lists | Solution | O(n*logk) | O(logk) | Hard | Heap | |
| 17 | Letter Combinations of a Phone Number | Solution | O(n*4^n) | O(n) | Medium | Backtracking | |
| 15 | 3Sum | Solution | O(nlogn) | O(1) | Medium | Two Pointers | |
| 10 | Regular Expression Matching | Solution | O(m*n) | O(m*n) | Hard | DP | |
| 8 | String to Integer (atoi) | Solution | O(n) | O(1) | Easy | | |
| 7 | Reverse Integer | Solution | O(1) | O(1) | Easy | | |
| 2 | Add Two Numbers | Solution | O(n) | O(1) | Medium | LinkedList | |
| 1 | Two Sum | Solution | O(n)/O(n^2) | O(1)/O(n) | Easy | HashMap | |