LeetCode

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Q: When is the best time to plant a tree?

A: Ten years ago.

Q: And when is the next best time?

A: Today.

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• 该仓库主要用于记录 LeetCode 题解

• 题解语言为 Swift、Java、JavaScript

• LeetCode：https://leetcode.cn/u/yujiuqie

• 个人博客：https://jhfs.fun

• 常见数据结构：数组、链表、栈、队列、散列表、二叉树、堆、跳表、图、Trie 树；

• 常见算法：递归、排序、二分查找、搜索、哈希算法、贪心算法、分治算法、回溯算法、动态规划、字符串匹配算法。

刷题记录

数组(Array)

Problem	Swift	Java	JavaScript	Note
1. Two Sum	Swift	Java	[JavaScript]
137. Single Number II	Swift	Java	[JavaScript]
605. Can Place Flowers	Swift	Java	[JavaScript]	贪心
896. Monotonic Array	Swift	Java	[JavaScript]
1060. Missing Element in Sorted Array	[Swift]	Java	[JavaScript]
1431. Kids With the Greatest Number of Candies	Swift	Java	[JavaScript]
1465. Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Swift	Java	[JavaScript]	贪心
1921. Eliminate Maximum Number of Monsters	[Swift]	Java	[JavaScript]
2511. Maximum Enemy Forts That Can Be Captured	[Swift]	Java	[JavaScript]
2652. Sum Multiples	Swift	Java	[JavaScript]
2682. Find the Losers of the Circular Game	Swift	Java	JavaScript

字符串(String)

Problem	Swift	Java	JavaScript	Note
43. Multiply Strings	Swift	Java	[JavaScript]
58. Length of Last Word	[Swift]	Java	[JavaScript]
833. Find And Replace in String	Swift	Java	JavaScript
1071. Greatest Common Divisor of Strings	[Swift]	Java	[JavaScript]
1768. Merge Strings Alternately	[Swift]	Java	[JavaScript]
2586. Count the Number of Vowel Strings in Range	Swift	Java	[JavaScript]
2609. Find the Longest Balanced Substring of a Binary String	Swift	Java	[JavaScript]
2678. Number of Senior Citizens	Swift	Java	[JavaScript]

双指针(Two Pointers)

Problem	Swift	Java	JavaScript	Note
228. Summary Ranges	[Swift]	Java	[JavaScript]
849. Maximize Distance to Closest Person	[Swift]	Java	[JavaScript]
1679. Max Number of K-Sum Pairs	[Swift]	Java	[JavaScript]
2337. Move Pieces to Obtain a String	[Swift]	Java	[JavaScript]
2562. Find the Array Concatenation Value	Swift	Java	[JavaScript]

滑动窗口(Sliding Window)

Problem	Swift	Java	JavaScript	Note
643. Maximum Average Subarray I	[Swift]	Java	[JavaScript]
1456. Maximum Number of Vowels in a Substring of Given Length	Swift	[Java]	[JavaScript]
1493. Longest Subarray of 1's After Deleting One Element	[Swift]	Java	[JavaScript]

哈希表(Hash)

Problem	Swift	Java	JavaScript	Note
187. Repeated DNA Sequences	Swift	Java	[JavaScript]	❎
383. Ransom Note	Swift	Java	[JavaScript]
1207. Unique Number of Occurrences	[Swift]	Java	[JavaScript]
1488. Avoid Flood in The City	Swift	Java	[JavaScript]	贪心
1657. Determine if Two Strings Are Close	[Swift]	Java	[JavaScript]
2605. Form Smallest Number From Two Digit Arrays	[Swift]	Java	[JavaScript]

矩阵(Matrix)

Problem	Swift	Java	JavaScript	Note
73. Set Matrix Zeroes	Swift	Java	[JavaScript]
2352. Equal Row and Column Pairs	[Swift]	Java	[JavaScript]
2596. Check Knight Tour Configuration	[Swift]	Java	[JavaScript]	DFS

区间(Intervals)

Problem	Swift	Java	JavaScript	Note
56. Merge Intervals	[Swift]	Java	[JavaScript]
57. Insert Interval	[Swift]	Java	[JavaScript]

栈(Stack)

Problem	Swift	Java	JavaScript	Note
2390. Removing Stars From a String	[Swift]	Java	[JavaScript]

单调栈(Monotonic Stack)

Problem	Swift	Java	JavaScript	Note
901. Online Stock Span	Swift	Java	[JavaScript]

队列(Queue)

Problem	Swift	Java	JavaScript	Note
649. Dota2 Senate	Swift	Java	[JavaScript]
933. Number of Recent Calls	[Swift]	Java	[JavaScript]

链表(Linked List)

Problem	Swift	Java	JavaScript	Note
2095. Delete the Middle Node of a Linked List	[Swift]	Java	[JavaScript]
2130. Maximum Twin Sum of a Linked List	Swift	Java	[JavaScript]

树（Tree General）

Problem	Swift	Java	JavaScript	Note
582. Kill Process	[Swift]	Java	[JavaScript]
1490. Clone N-ary Tree	[Swift]	Java	[JavaScript]
1506. Find Root of N-Ary Tree	[Swift]	Java	[JavaScript]
1522. Diameter of N-Ary Tree	[Swift]	Java	[JavaScript]

二叉树(Binary Tree General)

Problem	Swift	Java	JavaScript	Note
117. Populating Next Right Pointers in Each Node II	Swift	Java	[JavaScript]
250. Count Univalue Subtrees	Swift	Java	JavaScript
314. Binary Tree Vertical Order Traversal	Swift	Java	JavaScript
366. Find Leaves of Binary Tree	[Swift]	Java	[JavaScript]
545. Boundary of Binary Tree	[Swift]	Java	[JavaScript]
549. Binary Tree Longest Consecutive Sequence	Swift	Java	JavaScript
617. Merge Two Binary Trees	Swift	Java	JavaScript
872. Leaf-Similar Trees	[Swift]	Java	[JavaScript]	DFS
1161. Maximum Level Sum of a Binary Tree	Swift	Java	[JavaScript]
1120. Maximum Average Subtree	Swift	Java	JavaScript
1123. Lowest Common Ancestor of Deepest Leaves	[Swift]	Java	[JavaScript]
1372. Longest ZigZag Path in a Binary Tree	[Swift]	Java	[JavaScript]	DFS
1448. Count Good Nodes in Binary Tree	[Swift]	Java	[JavaScript]

二叉搜索树(Binary Search Tree)

Problem	Swift	Java	JavaScript	Note
255. Verify Preorder Sequence in Binary Search Tree	[Swift]	Java	[JavaScript]
272. Closest Binary Search Tree Value II	[Swift]	Java	[JavaScript]
333. Largest BST Subtree	[Swift]	Java	[JavaScript]
1214. Two Sum BSTs	[Swift]	Java	[JavaScript]
1373. Maximum Sum BST in Binary Tree	[Swift]	Java	[JavaScript]

图(Graph)

Problem	Swift	Java	JavaScript	Note
207. Course Schedule	[Swift]	Java	[JavaScript]	有向图拓扑排序
210. Course Schedule II	[Swift]	Java	[JavaScript]	有向图拓扑排序
277. Find the Celebrity	[Swift]	Java	[JavaScript]
1267. Count Servers that Communicate	[Swift]	Java	[JavaScript]
1462. Course Schedule IV	[Swift]	Java	[JavaScript]	有向图拓扑排序

图-深度优先搜索(Graph-DFS)

Problem	Swift	Java	JavaScript	Note
694. Number of Distinct Islands	[Swift]	Java	[JavaScript]
841. Keys and Rooms	Swift	Java	[JavaScript]
1059. All Paths from Source Lead to Destination	[Swift]	Java	[JavaScript]
2698. Find the Punishment Number of an Integer	Swift	Java	[JavaScript]

图-广度优先搜索(Graph-BFS)

Problem	Swift	Java	JavaScript	Note
286. Walls and Gates	[Swift]	Java	[JavaScript]
490. The Maze	[Swift]	Java	[JavaScript]
505. The Maze II	[Swift]	Java	[JavaScript]
994. Rotting Oranges	Swift	Java	[JavaScript]
1136. Parallel Courses	[Swift]	Java	[JavaScript]
1197. Minimum Knight Moves	[Swift]	Java	[JavaScript]
1236. Web Crawler	[Swift]	Java	[JavaScript]
1926. Nearest Exit from Entrance in Maze	Swift	Java	[JavaScript]

图-并查集(Graph-UFDS)

帮助解决 N 个元素的集合应用问题

Problem	Swift	Java	JavaScript	Note
200. Number of Islands	[Swift]	Java	[JavaScript]
305. Number of Islands II	[Swift]	Java	[JavaScript]
323. Number of Connected Components in an Undirected Graph	[Swift]	Java	[JavaScript]
1631. Path With Minimum Effort	[Swift]	Java	[JavaScript]
2316. Count Unreachable Pairs of Nodes in an Undirected Graph	Swift	Java	[JavaScript]	❎

字典树(Trie)

Problem	Swift	Java	JavaScript	Note
[]	[Swift]	[Java]	[JavaScript]

回溯(Backtracking)

Problem	Swift	Java	JavaScript	Note
247. Strobogrammatic Number II	[Swift]	Java	[JavaScript]	递归
254. Factor Combinations	[Swift]	Java	[JavaScript]	回溯
823. Binary Trees With Factors	[Swift]	Java	[JavaScript]	递归

分治(Divide And Conquer)

Problem	Swift	Java	JavaScript	Note
[]	[Swift]	[Java]	[JavaScript]

Kadane 算法(Kadane Algorithm)

Problem	Swift	Java	JavaScript	Note
[]	[Swift]	[Java]	[JavaScript]

二分查找(Binary Search)

Problem	Swift	Java	JavaScript	Note
74. Search a 2D Matrix	Swift	Java	[JavaScript]
374. Guess Number Higher or Lower	Swift	Java	[JavaScript]
1150. Check If a Number Is Majority Element in a Sorted Array	[Swift]	Java	[JavaScript]
1228. Missing Number In Arithmetic Progression	Swift	Java	JavaScript
1533. Find the Index of the Large Integer	[Swift]	Java	[JavaScript]
2560. House Robber IV	[Swift]	Java	[JavaScript]
2594. Minimum Time to Repair Cars	[Swift]	Java	[JavaScript]

堆(Heap)/优先级队列(Priority Queue)

• 优先级队列(Priority Queue)是堆(Heap)的一种应用，但优先级队列同样可以用其他数据结构实现，比如说直接对数组插入实现，但是效率不高。
• 区别：在 remove 操作中，Priority Queue 的时间复杂度是 O(n)，而 Heap 是 O(logn)。因为Priority Queue 需要找到这个数据，需要 O(n) 的时间，而 Heap 借助了 HashMap，所以只需要 O(1) 的时间就可以找到。

Problem	Swift	Java	JavaScript	Note
630. Course Schedule III	[Swift]	Java	[JavaScript]
1167. Minimum Cost to Connect Sticks	[Swift]	Java	[JavaScript]
2336. Smallest Number in Infinite Set	[Swift]	Java	[JavaScript]
2512. Reward Top K Students	[Swift]	Java	[JavaScript]
2530. Maximal Score After Applying K Operations	[Swift]	Java	[JavaScript]
2558. Take Gifts From the Richest Pile	[Swift]	Java	[JavaScript]

位运算(Bit Manipulation)

Problem	Swift	Java	JavaScript	Note
136. Single Number	Swift	Java	[JavaScript]
190. Reverse Bits	Swift	Java	[JavaScript]
231. Power of Two	[Swift]	Java	[JavaScript]
260. Single Number III	Swift	Java	[JavaScript]
318. Maximum Product of Word Lengths	Swift	Java	[JavaScript]
389. Find the Difference	Swift	Java	[JavaScript]
1318. Minimum Flips to Make a OR b Equal to c	Swift	Java	[JavaScript]

数学(Math)

Problem	Swift	Java	JavaScript	Note
1134. Armstrong Number	Swift	Java	JavaScript
1180. Count Substrings with Only One Distinct Letter	Swift	Java	JavaScript
2578. Split With Minimum Sum	Swift	Java	[JavaScript]	贪心
2582. Pass the Pillow	Swift	Java	[JavaScript]
2591. Distribute Money to Maximum Children	Swift	Java	JavaScript
2651. Calculate Delayed Arrival Time	Swift	Java	[JavaScript]

动态规划(DP)

Problem	Swift	Java	JavaScript	Note
53. Maximum Subarray	Swift	Java	[JavaScript]
121. Best Time to Buy and Sell Stock	Swift	Java	[JavaScript]
122. Best Time to Buy and Sell Stock II	Swift	Java	[JavaScript]
123. Best Time to Buy and Sell Stock III	Swift	Java	[JavaScript]
198. House Robber	[Swift]	Java	[JavaScript]
213. House Robber II	[Swift]	Java	[JavaScript]
256. Paint House	[Swift]	Java	[JavaScript]
276. Paint Fence	[Swift]	Java	[JavaScript]
300. Longest Increasing Subsequence	Swift	Java	[JavaScript]
309. Best Time to Buy and Sell Stock with Cooldown	Swift	Java	[JavaScript]
337. House Robber III	Swift	Java	[JavaScript]
646. Maximum Length of Pair Chain	Swift	Java	[JavaScript]
651. 4 Keys Keyboard	[Swift]	Java	[JavaScript]
673. Number of Longest Increasing Subsequence	Swift	Java	[JavaScript]
712. Minimum ASCII Delete Sum for Two Strings	Swift	Java	[JavaScript]
714. Best Time to Buy and Sell Stock with Transaction Fee	Swift	Java	[JavaScript]
740. Delete and Earn	Swift	Java	[JavaScript]
790. Domino and Tromino Tiling	Swift	Java	[JavaScript]
1218. Longest Arithmetic Subsequence of Given Difference	Swift	Java	[JavaScript]
1388. Pizza With 3n Slices	[Swift]	Java	[JavaScript]
1402. Reducing Dishes	Swift	Java	[JavaScript]
2240. Number of Ways to Buy Pens and Pencils	[Swift]	Java	[JavaScript]

前缀和(PrefixSum)

Problem	Swift	Java	JavaScript	Note
1732. Find the Highest Altitude	[Swift]	Java	[JavaScript]

设计(Design)

Problem	Swift	Java	JavaScript	Note
146. LRU Cache	Swift	Java	[JavaScript]
271. Encode and Decode Strings	[Swift]	Java	[JavaScript]
281. Zigzag Iterator	[Swift]	Java	[JavaScript]
604. Design Compressed String Iterator	Swift	Java	JavaScript	❎
1244. Design A Leaderboard	[Swift]	Java	[JavaScript]
1993. Operations on Tree	Swift	Java	[JavaScript]

模拟(Simulation)

Problem	Swift	Java	JavaScript	Note
LCP 50. Gem Supply	[Swift]	Java	[JavaScript]
1222. Queens That Can Attack the King	[Swift]	Java	[JavaScript]
2525. Categorize Box According to Criteria	Swift	Java	[JavaScript]

排序(Sorting)

Problem	Swift	Java	JavaScript	Note
1333. Filter Restaurants by Vegan-Friendly, Price and Distance	Swift	Java	[JavaScript]

笔记备忘

• ❎ - 程序逻辑正确，但力扣提交错误。
• 🇧 - 表示广度优先搜索解法。
• 🇩 - 表示深度优先搜索解法。
• 🇷 - 表示递归解法。
• 🅱️ - 表示回溯解法。

递归、深度优先搜索、回溯区别

• 🇷递归（Recursion）：递归是一种算法，在函数中调用自身的方法称为递归，是一种基于编程语言的实现方式。
• 🇩深度优先搜索（DFS）：深度优先搜索是一种算法思想，也是一种访问所有节点的方式，通常已经访问过的节点不再访问，所有点仅访问一次。深度优先搜索可以使用递归方式实现，也可以不使用递归方式实现。与深度优搜索（DFS）对应的是广度优先搜索（BFS）。
• 🅱️回溯（Backtracking）：回溯是一种算法思想，常用递归方式来实现，同时也是深度优先搜索的一种特例，与深度优先搜索的区别在于已经访问过的点可能再次访问，也可能存在没有被访问过的点（在满足一定条件后可以直接返回上一层）。

Swift 备注

• PriorityQueue 需要自定义实现

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优质算法解析

• 前缀和数组
• 线段树详解「汇总级别整理 🔥🔥🔥」

算法题组合

组合-1(132题)

• 数组:283、27、26、80、75、88、215、167、125、344、345、11、209、3、438、76
• 哈希表:349、350、242、202、290、205、415、1、15、18、16、454、49、447、149、219、217、220
• 链表:206、92、83、86、328、2、445、203、82、21、24、25、147、148、237、19、61、143、234
• 栈:20、150、71、144、94、145、341
• 队列:102、107、103、199、279、127、126
• 优先队列:347、23
• 二叉树:104、111、226、100、101、222、110、112、111、404、257、113、129、437、235、98、450、108、230、236
• 递归与回溯:17、93、131、46、47、77、39、40、216、78、90、401、79、200、130、417、51、52、37
• 动态规划:70、120、64、343、279、91、62、63、198、213、337、309、300、376、416、322、377、474、139、494
• 贪心:455、392、435、279

参考链接

• GitHub - LeetCode-Go
• GitHub - swift-algorithm-club
• GitHub - 宫水三叶的刷题日记