LeetCode

👉 2020 ~ 2022 两周年纪念！已达成 1000+ LeetCode题 & LeetCode Contest World Rating 前 10% 小成就。

🎉 目前已拿到多家互联网后端/国企/银行软开的21届offer，笔试及面试手撕环节 AC 率 95%。

希望能帮助到还在准备北美SDE、国内秋招&春招技术开发岗的各位，欢迎大家pull request一起完善！

👉 有需要 LeetCode 会员账号、或需要解锁查看内容的、有问题都欢迎私信我，我的会员2022年11月到期。

我的LeetCode刷题、思路和代码总结，以及常见算法模板。欢迎在仓库内搜索题解（since 2020， 目前工作繁忙，更新较慢）.

欢迎各位star！便于日常学习/面试/笔试前复习，重在积累和思路，因为题目是做不完！

刷题方法

• 初期：题解标题下有原题链接，先自我思考5-10分钟，没有思路的话，立即“抄答案”，备考前期不要贪题量，每周保证每个 Tag 背熟 3 ~ 5 个 Medium 难度的经典题。
  • 背熟！！：算法模板代码👆（二分查找、单链表、堆排序、归并排序、快速排序、并查集、Trie 前缀树等）
  • 经典模板题！：Tag 分类👇，以及：
    • 各种双指针问题、栈（Stack/深搜，题号232, 150, 224, 20, 1472, 1249）、队列（Queue/宽搜/二叉树层序遍历，225, 346, 1429, 54）、堆（Heap/Priority Queue/前K最值问题，347, 23, 692, 895, 295, 1438(Google原题)）
    • 84. 直方图最大矩形
    • 53. 最大连续子数组的和、300. 最长上升子序列 LIS、最长上升公共子序列、最长连续不重复的子序列
    • 股票买卖系列
    • 经典DFS/BFS搜索问题：0/1二维矩阵求岛屿数量(LC 200)，迷宫最短路、太平洋大西洋
    • 更新中....
• 中期：能够举一反三，在 LeetCode 搜索类似题目，最好能够一边讲思路、一边写代码。
• 后期突击：强烈建议大家使用 codeTop。

Tag

题目列表

Two Pointers

• Pair with Target Sum (模板)
• Remove Duplicates (模板)
• Triplet Sum to Zero (模板)
  • Follow up: Triplet Sum Close to Target
• Subarrays with Product Less than a Target (medium)
• Dutch National Flag Problem (medium) / 三色旗 / 颜色分类
• 4Sum
• 1537. Get the Maximum Score (Hard)
• 42. Trapping Rain Water
• 434. Number of Segments in a String

Dynamic Programming

• 10. Regular Expression Matching 字符匹配
• 45. Jump Game 2
• 91. Decode Ways
• 198. House Robber
• 337. House Robber III
• 256. Paint House
• 265. Paint House 2 (Hard)
• 221. Maximal Square (Medium)
• 494. Target Sum (Medium)
• 746. Min Cost Climbing Stairs
• 279. Perfect Squares
• 63. Unique Paths
• 322. Coin Change
• 518. Coin Change 2
• 486. Predict the Winner
• 377. Combination Sum IV
• 131. Palindrome Partitioning 最长回文串划分
• 516. Longest Palindromic Subsequence 最长回文串子序列个数
• 139. Word Break
• 1524. Number of Sub-arrays With Odd Sum
• 403. Frog Jump
• 1423. Maximum Points You Can Obtain from Cards
• 1143. Longest Common Subsequence (经典，模板题)
• 718. Maximum Length of Repeated Subarray (与上题相似)
• 1312. Minimum Insertion Steps to Make a String Palindrome (记忆化递归, DP数组)
• 1155. Number of Dice Rolls With Target Sum (记忆化递归, DP数组)
• 1679. Max Number of K-Sum Pairs (HashMap)

Tree

• 96. Unique Binary Search Tree
• 95. Unique Binary Search Trees II
• 98. Validate a BST
• 99. Recover Binary Search Tree (Hard)
• 100. Same Tree (easy)
• 101. Symmetric Tree (easy)
• 110. Balanced Binary Tree
• 111. Minimum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 108. Convert Sorted Array to Binary Search Tree (Easy)
• 538. Convert BST to Greater Tree
• 1038. Binary Search Tree to Greater Sum Tree (Same as 538)
• 107. 层序遍历
• 112. Path Sum
• 113. Path Sum II
• 116. Populating Next Right Pointers in Each Node
• 437. Path Sum III (easy)
• 124. Binary Tree Maximum Path Sum
• 306. Find Leaves of Binary Tree
• 701. Insert into a BST
• 572. Subtree of Another Tree
• 510. In-order Successor in BST II
• 449. Serialize and Deserialize BST (序列化:Node->String 和反序列化: String->Node)
• 236. Lowest Common Ancestor of a Binary Tree (经典, LCA 公共祖先问题)
• 1302. Deepest Leaves Sum

Linked List

• 19. Remove Nth Node From End of List
• 24. Swap Nodes in Pair
• 141. Linked List Cycle
• 147. Insertion Sort List
• 160. Intersection of Two Linked Lists
• 109. Convert Sorted List to BST
• 206. Reverse Linked List (经典 每日一题)
• 25. Reverse Node in k-Group (经典 Hard)
• 92. Reverse Linked List II (经典)
• 328. Odd Even Linked List
• 82. Remove Duplicates from Sorted List II

Depth-First-Search

• 79. Word Search
• 130. Surrounded Regions
• 200. Numbers of Islands (三种方法, 经典)
• 694. Number of Distinct Islands
• 695. Max Area of Island
• 547. Friend Circles
• 733. Flood Fill (经典)
• 967. Numbers With Same Consecutive Differences
• 980. Unique Paths III (Hard)
• 934. Shortest Bridge (BFS + DFS)
• 417. Pacific Atlantic Water Flow (大平洋大西洋水流, 经典模板题)

Breath-First-Search

• 207. Course Schedule (经典)
• 210. Course Schedule II (经典)
• 934. Shortest Bridge (BFS + DFS)
• 994. Rotting Oranges
• 417. Pacific Atlantic Water Flow (大平洋大西洋水流, 经典模板题)

Graph

• 207. Course Schedule (经典)
• 210. Course Schedule II (经典)
• 399. Evaluate Division (Graph + BFS)
• 269. Alien Dictionary (Graph + BFS)
• 1192. Critical Connections in a Network (Hard)
• 277. Find the Celebrity
• 133. Clone Graph
• 863. All Nodes Distance K in Binary Tree
• 1334. Find the City With the Smallest Number of Neighbors at a Threshold Distance (Floyd-warshall 最短路径)
• 684. Redundant Connection (DFS, 并查集Union-Find)

Greedy

• 1029. Two City Scheduling
• 406. Queue Reconstruction by Height
• 435. Non-overlapping Intervals

Binary Search

• 162. Find Peak Element
• 4. Median of Two Sorted Arrays (Hard)
• 729. My Calendar I
• 33. Search in Rotated Sorted Array
• 34. Find First and Last Position of Element in Sorted Array
• 74. Search a 2D Matrix
• 153. Find Minimum in Rotated Sorted Array
• 209. Minimum Size Subarray Sum
• 230. Kth Smallest Element in a BST
• 240. Search a 2D Matrix II
• 270. Closest Binary Search Tree Value
• 287. Find the Duplicate Number
• 300. Longest Increasing Subsequence
• 315. Count of Smaller Numbers After Self
• 374. Guess Number Higher or Lower
• 410. Split Array Largest Sum (经典Hard, 二分+贪心)
• 875. Koko Eating Bananas
• 1283. Find the Smallest Divisor Given a Threshold
• 1337. The K Weakest Rows in a Matrix
• 1351. Count Negative Numbers in a Sorted Matrix

Sliding Window

• 3. Longest Substring Without Repeating Characters
• 340. Longest Substring with At Most K Distinct Characters
• 76. Minimum Window Substring
• 30. Substring with Concatenation of All Words
• 模板题：String Anagrams (hard)
• 模板题：Permutation in a String (hard)

Merge Intervals (区间问题)

• 模板题: Merge Intervals (合并区间)
• 模板题: Insert Interval (插入区间)
• 模板题: Intervals Intersection (查找交集)
• 模板题: Conflicting Appointments (冲突区间)
• 模板题: Minimum Meeting Rooms (最少的会议室)
• Maximum CPU Load
• Employee Free Time (Hard)
• 729. My Calendar I
• 435. Non-overlapping Intervals (Greedy Method)
• 1272. Remove Interval

Subset

• 78. Subsets
• 90. Subsets II

BackTracking

• 17. Letter Combinations of a Phone Number
• 22. Generate Parentheses
• 51. N皇后问题
• 46. Permutation
• 47. Permutations II
• 216. Combination Sum III
• 1718. Construct the Lexicographically Largest Valid Sequence (回溯, 暴力搜索)

Stack

• 84. Largest Rectangle in Histogram 直方图最大面积
• 232. Implement Queue using Stacks 利用栈实现队列
• 402. Remove K Digits
• 946. Validate Stack Sequences
• 71. Simplify Path
• 739. Daily Temperatures

Heap / Heap Sort

• 973. K Closest Points to Origin (Medium)
• 378. Kth Smallest Element in a Sorted Matrix
• 295. Find Median from Data Stream (Hard)

Design

• 146. LRU Cache (每日一题)
• 380. Insert Delete GetRandom O(1) (每日一题)
• 208. Implement Trie (Prefix Tree)
• 212. Word Search II
• 211. Add and Search Word - Data structure design
• 1286. Iterator for Combination (Google)
• 1032. Stream of Characters (Use Trie)
• 362. Design Hit Counter

Array

• 41. First Missing Positive
• 238. Product of Array Except Self
• 179. Largest Number
• 498. Diagonal Traverse
• 334. Increasing Triplet Subsequence
• 442. Find All Duplicates in an Array
• 406. Queue Reconstruction by Height
• 624. Maximum Distance in Arrays
• 910. Smallest Range II
• 243. Shortest Word Distance
• 153. Find Minimum in Rotated Sorted Array (无重复元素)
• 154. Find Minimum in Rotated Sorted Array II (有重复元素)
• 1413. Minimum Value to Get Positive Step by Step Sum

String

• 10. Regular Expression Matching 字符匹配
• 32. Longest Valid Parentheses (经典)
• 38. Count and Say
• 44. Wildcard Matching 万卡匹配
• 97. Interleaving String (hard)
• 929. Unique Email Addresses
• 1041. Robot Bounded In Circle
• 763. Partition Labels
• 1505. Minimum Possible Integer After at Most K Adjacent Swaps On Digits
• 1291. Sequential Digits
• 468. Validate IP Address
• 556. Next Greater Element III

Palindrome

• 5. Longest Palindromic Substring (经典)
• 131. Palindrome Partitioning
• 214. Shortest Palindrome (Hard)
• 234. Palindrome Linked List (Easy)
• 266. Palindrome Permutation (Easy)
• 336.Palindrome Pairs (Hard, Amazon)
• 409. Longest Palindrome
• 516. Longest Palindromic Subsequence
• 647. Palindromic Substrings
• 1312. Minimum Insertion Steps to Make a String Palindrome (记忆化递归, DP数组)
• 680. Valid Palindrome II (Easy)

Bit Manipulation

• 421. Maximum XOR of Two Numbers in an Array (Use Trie)