[简体中文](./README.md) | English


LeetCode Solutions: A Record of My Problem Solving Journey.

This repository will be divided into four parts for now:

- The first part is the solutions to some classic problems on LeetCode, including the idea thinkings, key points and code implementations.

- The second part is the summary of data structures and algorithms.

- The third part is[Anki flashcards](https://apps.ankiweb.net) that record the LeetCode problems in a certain way so as to make it easier to remember.

- The fourth part is future plans on content that would be introduced into the above parts.

- For the parts that were added recently, there will be a 🆕 behind.

- For the parts that were updated recently, there will be a 🖊 behind.

- Here will be the place to update Anki Flashcards in the future as well.

- Here is a mind mapping graph showing the summary of categorizations of problems that are questioned frequently in interviews. We could analyze according to the information in the graph.


(Picture credited by[LeetCode-cn](https://www.zhihu.com/question/24964987/answer/586425979).)

The algorithms mainly includes:

- Basic skills: Divide-and-Conquer; Binary; Greedy

- Sorting algorithms: Quicksort; Merge Sort; Counting Sort

- Searching algorithms: Backtracking; Recursion; Depth-First-Search (DFS); Breath-First-Search (BFS); Binary Search Tree; etc.

- Graph theory: Shortest Path Problem; Minimal Spanning Tree

- Dynamic Programming: Knapsack Problem; Longest Common Subsequence (LCS) Problem

The data structures mainly includes:

- Array and linked list: Singly/Doubly-Linked List

- Stack and queue

- Hash table

- Heap: Min-Max Heap

- Tree and Graph: Lowest Common Ancestor (LCA); Disjoint-Set

- String: Prefix Tree (Trie); Suffix Tree

[0042.trapping-rain-water](./problems/42.trapping-rain-water.md):


[Stack in Browser](./thinkings/basic-data-structure.md)：


[backtrack problems](./problems/90.subsets-ii.md):


[0198.house-robber](./problems/198.house-robber.md):


[0454.4-sum-ii](./problems/454.4-sum-ii.md):


-[Top 100 Linked Questions](https://leetcode.com/problemset/top-100-liked-questions/) (44 / 100)

-[Top Interview Questions](https://leetcode.com/problemset/top-interview-questions/) (64 / 145)

-[0020.Valid Parentheses](./problems/20.validParentheses.md)

-[0026.remove-duplicates-from-sorted-array](./problems/26.remove-duplicates-from-sorted-array.md)

-[0088.merge-sorted-array](./problems/88.merge-sorted-array.md)

-[0121.best-time-to-buy-and-sell-stock](./problems/121.best-time-to-buy-and-sell-stock.md) 🆕

-[0122.best-time-to-buy-and-sell-stock-ii](./problems/122.best-time-to-buy-and-sell-stock-ii.md) 🆕

-[0136.single-number](./problems/136.single-number.md)

-[0167.two-sum-ii-input-array-is-sorted](./problems/167.two-sum-ii-input-array-is-sorted.md)

-[0169.majority-element](./problems/169.majority-element.md)

-[0190.reverse-bits](./problems/190.reverse-bits.md)

-[0191.number-of-1-bits](./problems/191.number-of-1-bits.md)

-[0198.house-robber](./problems/198.house-robber.md) 🆕

-[0203.remove-linked-list-elements](./problems/203.remove-linked-list-elements.md)

-[0206.reverse-linked-list](./problems/206.reverse-linked-list.md)

-[0219.contains-duplicate-ii](./problems/219.contains-duplicate-ii.md)

-[0226.invert-binary-tree](./problems/226.invert-binary-tree.md)

-[0283.move-zeroes](./problems/283.move-zeroes.md)

-[0349.intersection-of-two-arrays](./problems/349.intersection-of-two-arrays.md)

-[0002. Add Two Numbers](./problems/2.addTwoNumbers.md)

-[0003. Longest Substring Without Repeating Characters](./problems/3.longestSubstringWithoutRepeatingCharacters.md)

-[0011.container-with-most-water](./problems/11.container-with-most-water.md)

-[0015.3-sum](./problems/15.3-sum.md) 🆕

-[0019. Remove Nth Node From End of List](./problems/19.removeNthNodeFromEndofList.md)

-[0024. Swap Nodes In Pairs](./problems/24.swapNodesInPairs.md)

-[0039.combination-sum](./problems/39.combination-sum.md)

-[0040.combination-sum-ii](./problems/40.combination-sum-ii.md)

-[0046.permutations](./problems/46.permutations.md)

-[0047.permutations-ii](./problems/47.permutations-ii.md)

-[0055.jump-game](./problems/55.jump-game.md) 🆕

-[0062.unique-paths](./problems/62.unique-paths.md)🆕

-[0075.sort-colors](./problems/75.sort-colors.md)

-[0078.subsets](./problems/78.subsets.md) 🆕

-[0086.partition-list](./problems/86.partition-list.md)

-[0090.subsets-ii](./problems/90.subsets-ii.md)

-[0091.decode-ways](./problems/91.decode-ways.md) 🆕

-[0092.reverse-linked-list-ii](./problems/92.reverse-linked-list-ii.md)

-[0094.binary-tree-inorder-traversal](./problems/94.binary-tree-inorder-traversal.md)

-[0102.binary-tree-level-order-traversal](./problems/102.binary-tree-level-order-traversal.md)

-[0103.binary-tree-zigzag-level-order-traversal](./problems/103.binary-tree-zigzag-level-order-traversal.md)

-[0139.word-break](./problems/139.word-breakmd)

-[0144.binary-tree-preorder-traversal](./problems/144.binary-tree-preorder-traversal.md)

-[0150.evaluate-reverse-polish-notation](./problems/150.evaluate-reverse-polish-notation.md) 🖊

-[0152.maximum-product-subarray](./problems/152.maximum-product-subarray.md) 🆕

-[0199.binary-tree-right-side-view](./problems/199.binary-tree-right-side-view.md)

-[0201.bitwise-and-of-numbers-range](./problems/201.bitwise-and-of-numbers-range.md)

-[0208.implement-trie-prefix-tree](./problems/208.implement-trie-prefix-tree.md) 🆕

-[0209.minimum-size-subarray-sum](./problems/209.minimum-size-subarray-sum.md) 🖊

-[0236.lowest-common-ancestor-of-a-binary-tree](./problems/236.lowest-common-ancestor-of-a-binary-tree.md)🆕

-[0238.product-of-array-except-self](./problems/238.product-of-array-except-self.md) 🆕

-[0240.search-a-2-d-matrix-ii](./problems/240.search-a-2-d-matrix-ii.md)

-[0279.perfect-squares](./problems/279.perfect-squares.md)

-[0309.best-time-to-buy-and-sell-stock-with-cooldown](./problems/309.best-time-to-buy-and-sell-stock-with-cooldown.md) 🆕

-[0322.coin-change](./problems/322.coin-change.md)

-[0334.increasing-triplet-subsequence](./problems/334.increasing-triplet-subsequence.md)

-[0328.odd-even-linked-list](./problems/328.odd-even-linked-list.md)

-[0416.partition-equal-subset-sum](./problems/416.partition-equal-subset-sum.md)

-[0445.add-two-numbers-ii](./problems/445.add-two-numbers-ii.md)

-[0454.4-sum-ii](./problems/454.4-sum-ii.md) 🆕

-[0494.target-sum](./problems/494.target-sum.md) 🆕

-[0518.coin-change-2](./problems/518.coin-change-2.md)

-[0875.koko-eating-bananas](./problems/875.koko-eating-bananas.md)

-[0877.stone-game](./problems/877.stone-game.md)

-[0887.super-egg-drop](./problems/887.super-egg-drop.md)

-[0900.rle-iterator](./problems/900.rle-iterator.md)

-[0023.merge-k-sorted-lists](./problems/23.merge-k-sorted-lists.md)

-[0042.trapping-rain-water](./problems/42.trapping-rain-water.md)

-[0128.longest-consecutive-sequence](./problems/128.longest-consecutive-sequence.md) 🆕

-[0145.binary-tree-postorder-traversal](./problems/145.binary-tree-postorder-traversal.md)

-[0146.lru-cache](./problems/146.lru-cache.md)

-[0239.sliding-window-maximum](./problems/239.sliding-window-maximum.md)

-[0295.find-median-from-data-stream](./problems/295.find-median-from-data-stream.md) 🆕

-[0301.remove-invalid-parentheses](./problems/301.remove-invalid-parentheses.md)

- 🖊[Data Structure](./thinkings/basic-data-structure.md) (Drafts)

- 🖊[Binary Tree Traversal](./thinkings/binary-tree-traversal.md)

-[Dynamic Programming](./thinkings/dynamic-programming.md)

-[Huffman Encode and Run Length Encode](./thinkings/run-length-encode-and-huffman-encode.md)

-[Bloom Filter](./thinkings/bloom-filter.md)

Anki falshcards would be mainly two parts: the mappings from key points to problems; the mappings from problems to idea thinks, key points and code implementations.

All flashcards are put in[anki-card](./assets/anki/leetcode.apkg).

Latest updated flashcards (only lists the front page):

- What is the key point of the binary search algorithm? Related problems?

- How to simplify the operations using the features of stacks? Related problems?

- The thinkings and related problems of double-pointers problems?

- The thinkings and related problems of sliding window problems?

- The thinkings and related problems of backtracking?

-[0494.target-sum](./todo/494.target-sum.js)

-[0609.find-duplicate-file-in-system](./todo/609.find-duplicate-file-in-system.js)

-[0010.regular-expression-matching](./todo/10.regular-expression-matching.js)

-[0309.best-time-to-buy-and-sell-stock-with-cooldown](./todo/309.best-time-to-buy-and-sell-stock-with-cooldown.js)

-[0365.water-and-jug-problem](./todo/365.water-and-jug-problem.js)

-[Complete Anki Flashcards](./assets/anki/)

-[Collection of String Problem](./todo/str/)

We're still on the early stage, so feedback from community is very welcome. For sake of reducing the costs of communication, I created some chat groups.



(Add this bot and reply "leetcode" to join the group.)

- If you have any ideas,[Issues](https://github.com/azl397985856/leetcode/issues) or chat in groups.

- If you want to commit to the repository, Pull Request is welcome.

- If you want to edit images resources in this project,[here](./assets/drawio/) lists the files that can be edited on[draw.io](https://www.draw.io/).

简体中文 |[English](./README.en.md)


leetcode 题解，记录自己的 leetcode 解题之路。

本仓库目前分为四个部分：

现在还是初级阶段，需要大家的意见和反馈，为了减少沟通成本，我组建了交流群。大家可以扫码进入



(由于微信的限制，100个人以上只能邀请加入， 你可以添加我的机器人回复“leetcode”拉你进群)

- 如果有想法和创意，请提[issue](https://github.com/azl397985856/leetcode/issues)或者进群提

- 如果想贡献代码，请提[PR](https://github.com/azl397985856/leetcode/pulls)

- 如果需要修改项目中图片，[这里](./assets/drawio/)存放了项目中绘制图的源代码， 大家可以用[draw.io](https://www.draw.io/)打开进行编辑。

- 如果需要修改项目中图片，[这里](./assets/drawio/)存放了项目中绘制图的源代码， 大家可以用[draw.io](https://www.draw.io/)打开进行编辑。