LeetCode in Go

LeetCode Online Judge is a website containing many algorithm questions. Most of them are real interview questions of Google, Facebook, LinkedIn, Apple, etc. and it always help to sharp our algorithm Skills. Level up your coding skills and quickly land a job. This is the best place to expand your knowledge and get prepared for your next interview. This repo shows my solutions in Go with the code style strictly follows the Google Golang Style Guide. Please feel free to reference and STAR to support this repo, thank you!

支持 Progressive Web Apps 和 Dark Mode 的题解电子书《LeetCode Cookbook》 Online Reading

离线版本的电子书《LeetCode Cookbook》PDF Download here

通过 iOS / Android 浏览器安装 PWA 版《LeetCode Cookbook》至设备桌面随时学习

Data Structures

标识了 ✅ 的专题是完成所有题目了的，没有标识的是还没有做完所有题目的

• Array
• String
• ✅ Two Pointers
• ✅ Linked List
• ✅ Stack
• Tree
• Dynamic programming
• ✅ Backtracking
• Depth First Search
• Breadth First Search
• Binary Search
• Math
• Hash Table
• ✅ Sort
• ✅ Bit Manipulation
• ✅ Union Find
• ✅ Sliding Window
• ✅ Segment Tree
• ✅ Binary Indexed Tree

数据结构	变种	相关题目	讲解文章
顺序线性表：向量
单链表	1. 双向链表 2. 静态链表 3. 对称矩阵 4. 稀疏矩阵
哈希表	1. 散列函数 2. 解决碰撞/填充因子
栈和队列	1. 广义栈 2. 双端队列
队列	1. 链表实现 2. 循环数组实现 3. 双端队列
字符串	1. KMP算法 2. 有限状态自动机 3. 模式匹配有限状态自动机 4. BM 模式匹配算法 5. BM-KMP 算法 6. BF 算法
树	1. 二叉树 2. 并查集 3. Huffman 树
数组实现的堆	1. 极大堆和极小堆 2. 极大极小堆 3. 双端堆 4. d 叉堆
树实现的堆	1. 左堆 2. 扁堆 3. 二项式堆 4. 斐波那契堆 5. 配对堆
查找	1. 哈希表 2. 跳跃表 3. 排序二叉树 4. AVL 树 5. B 树 / B+ 树 / B* 树 6. AA 树 7. 红黑树 8. 排序二叉堆 9. Splay 树 10. 双链树 11. Trie 树 12. R 树
--------------------------------------------	--------------------------------------------------------------------------------------------	---------------------------	-----------------------------------

Algorithm

算法	具体类型	相关题目	讲解文章
排序算法	1. 冒泡排序 2. 插入排序 3. 选择排序 4. 希尔 Shell 排序 5. 快速排序 6. 归并排序 7. 堆排序 8. 线性排序算法 9. 自省排序 10. 间接排序 11. 计数排序 12. 基数排序 13. 桶排序 14. 外部排序 - k 路归并败者树 15. 外部排序 - 最佳归并树
递归与分治		1. 二分搜索/查找 2. 大整数的乘法 3. Strassen 矩阵乘法 4. 棋盘覆盖 5. 合并排序 6. 快速排序 7. 线性时间选择 8. 最接近点对问题 9. 循环赛日程表
动态规划		1. 矩阵连乘问题 2. 最长公共子序列 3. 最大子段和 4. 凸多边形最优三角剖分 5. 多边形游戏 6. 图像压缩 7. 电路布线 8. 流水作业调度 9. 0-1 背包问题/背包九讲 10. 最优二叉搜索树 11. 动态规划加速原理 12. 树型 DP
贪心		1. 活动安排问题 2. 最优装载 3. 哈夫曼编码 4. 单源最短路径 5. 最小生成树 6. 多机调度问题
回溯法		1. 装载问题 2. 批处理作业调度 3. 符号三角形问题 4. n 后问题 5. 0-1 背包问题 6. 最大团问题 7. 图的 m 着色问题 8. 旅行售货员问题 9. 圆排列问题 10. 电路板排列问题 11. 连续邮资问题
搜索	1. 枚举 2. DFS 3. BFS 4. 启发式搜索
随机化	1. 随机数 2. 数值随机化算法 3. Sherwood 舍伍德算法 4. Las Vegas 拉斯维加斯算法 5. Monte Carlo 蒙特卡罗算法	1. 计算 π 值 2. 计算定积分 3. 解非线性方程组 4. 线性时间选择算法 5. 跳跃表 6. n 后问题 7. 整数因子分解 8. 主元素问题 9. 素数测试
图论	1. 遍历 DFS / BFS 2. AOV / AOE 网络 3. Kruskal 算法(最小生成树) 4. Prim 算法(最小生成树) 5. Boruvka 算法(最小生成树) 6. Dijkstra 算法(单源最短路径) 7. Bellman-Ford 算法(单源最短路径) 8. SPFA 算法(单源最短路径) 9. Floyd 算法(多源最短路径) 10. Johnson 算法(多源最短路径) 11. Fleury 算法(欧拉回路) 12. Ford-Fulkerson 算法(最大网络流增广路) 13. Edmonds-Karp 算法(最大网络流) 14. Dinic 算法(最大网络流) 15. 一般预流推进算法 16. 最高标号预流推进 HLPP 算法 17. Primal-Dual 原始对偶算法(最小费用流)18. Kosaraju 算法(有向图强连通分量) 19. Tarjan 算法(有向图强连通分量) 20. Gabow 算法(有向图强连通分量) 21. 匈牙利算法(二分图匹配) 22. Hopcroft－Karp 算法(二分图匹配) 23. kuhn munkras 算法(二分图最佳匹配) 24. Edmonds’ Blossom-Contraction 算法(一般图匹配)	1. 图遍历 2. 有向图和无向图的强弱连通性 3. 割点/割边 3. AOV 网络和拓扑排序 4. AOE 网络和关键路径 5. 最小代价生成树/次小生成树 6. 最短路径问题/第 K 短路问题 7. 最大网络流问题 8. 最小费用流问题 9. 图着色问题 10. 差分约束系统 11. 欧拉回路 12. 中国邮递员问题 13. 汉密尔顿回路 14. 最佳边割集/最佳点割集/最小边割集/最小点割集/最小路径覆盖/最小点集覆盖 15. 边覆盖集 16. 二分图完美匹配和最大匹配问题 17. 仙人掌图 18. 弦图 19. 稳定婚姻问题 20. 最大团问题
数论		1. 最大公约数 2. 最小公倍数 3. 分解质因数 4. 素数判定 5. 进制转换 6. 高精度计算 7. 整除问题 8. 同余问题 9. 欧拉函数 10. 扩展欧几里得 11. 置换群 12. 母函数 13. 离散变换 14. 康托展开 15. 矩阵 16. 向量 17. 线性方程组 18. 线性规划
几何		1. 凸包 - Gift wrapping 2. 凸包 - Graham scan 3. 线段问题 4. 多边形和多面体相关问题
NP 完全	1. 计算模型 2. P 类与 NP 类问题 3. NP 完全问题 4. NP 完全问题的近似算法	1. 随机存取机 RAM 2. 随机存取存储程序机 RASP 3. 图灵机 4. 非确定性图灵机 5. P 类与 NP 类语言 6. 多项式时间验证 7. 多项式时间变换 8. Cook定理 9. 合取范式的可满足性问题 CNF-SAT 10. 3 元合取范式的可满足性问题 3-SAT 11. 团问题 CLIQUE 12. 顶点覆盖问题 VERTEX-COVER 13. 子集和问题 SUBSET-SUM 14. 哈密顿回路问题 HAM-CYCLE 15. 旅行售货员问题 TSP 16. 顶点覆盖问题的近似算法 17. 旅行售货员问题近似算法 18. 具有三角不等式性质的旅行售货员问题 19. 一般的旅行售货员问题 20. 集合覆盖问题的近似算法 21. 子集和问题的近似算法 22. 子集和问题的指数时间算法 23. 子集和问题的多项式时间近似格式
------------	------------------------------------------------------------------	-----------------------------------------------------------------	--------------------

LeetCode Problems

一. 个人数据

	Easy	Medium	Hard	Total
Optimizing	36	43	16	95
Accepted	272	348	103	723
Total	468	945	380	1793
Perfection Rate	86.8%	87.6%	84.5%	86.9%
Completion Rate	58.1%	36.8%	27.1%	40.3%
------------	----------------------------	----------------------------	----------------------------	----------------------------

二. 目录

以下已经收录了 628 道题的题解，还有 12 道题在尝试优化到 beats 100%

No.	Title	Solution	Acceptance	Difficulty	Frequency
0001	Two Sum	Go	46.6%	Easy
0002	Add Two Numbers	Go	35.5%	Medium
0003	Longest Substring Without Repeating Characters	Go	31.5%	Medium
0004	Median of Two Sorted Arrays	Go	31.2%	Hard
0005	Longest Palindromic Substring	Go	30.6%	Medium
0006	ZigZag Conversion	Go	38.1%	Medium
0007	Reverse Integer	Go	25.9%	Easy
0008	String to Integer (atoi)	Go	15.7%	Medium
0009	Palindrome Number	Go	49.9%	Easy
0010	Regular Expression Matching		27.4%	Hard
0011	Container With Most Water	Go	52.8%	Medium
0012	Integer to Roman	Go	57.0%	Medium
0013	Roman to Integer	Go	56.9%	Easy
0014	Longest Common Prefix		36.1%	Easy
0015	3Sum	Go	28.1%	Medium
0016	3Sum Closest	Go	46.3%	Medium
0017	Letter Combinations of a Phone Number	Go	49.3%	Medium
0018	4Sum	Go	35.0%	Medium
0019	Remove Nth Node From End of List	Go	35.8%	Medium
0020	Valid Parentheses	Go	39.9%	Easy
0021	Merge Two Sorted Lists	Go	56.2%	Easy
0022	Generate Parentheses	Go	65.5%	Medium
0023	Merge k Sorted Lists	Go	42.8%	Hard
0024	Swap Nodes in Pairs	Go	53.2%	Medium
0025	Reverse Nodes in k-Group	Go	45.0%	Hard
0026	Remove Duplicates from Sorted Array	Go	46.6%	Easy
0027	Remove Element	Go	49.3%	Easy
0028	Implement strStr()	Go	35.3%	Easy
0029	Divide Two Integers	Go	16.9%	Medium
0030	Substring with Concatenation of All Words	Go	26.3%	Hard
0031	Next Permutation	Go	33.8%	Medium
0032	Longest Valid Parentheses		29.3%	Hard
0033	Search in Rotated Sorted Array	Go	36.0%	Medium
0034	Find First and Last Position of Element in Sorted Array	Go	37.4%	Medium
0035	Search Insert Position	Go	42.8%	Easy
0036	Valid Sudoku	Go	50.7%	Medium
0037	Sudoku Solver	Go	46.7%	Hard
0038	Count and Say		46.1%	Medium
0039	Combination Sum	Go	59.4%	Medium
0040	Combination Sum II	Go	50.2%	Medium
0041	First Missing Positive	Go	33.8%	Hard
0042	Trapping Rain Water	Go	51.3%	Hard
0043	Multiply Strings	Go	35.0%	Medium
0044	Wildcard Matching		25.5%	Hard
0045	Jump Game II	Go	31.5%	Medium
0046	Permutations	Go	66.8%	Medium
0047	Permutations II	Go	49.5%	Medium
0048	Rotate Image	Go	60.1%	Medium
0049	Group Anagrams	Go	59.4%	Medium
0050	Pow(x, n)	Go	31.0%	Medium
0051	N-Queens	Go	49.8%	Hard
0052	N-Queens II	Go	60.3%	Hard
0053	Maximum Subarray	Go	47.8%	Easy
0054	Spiral Matrix	Go	36.2%	Medium
0055	Jump Game	Go	35.2%	Medium
0056	Merge Intervals	Go	41.2%	Medium
0057	Insert Interval	Go	35.2%	Medium
0058	Length of Last Word		33.5%	Easy
0059	Spiral Matrix II	Go	58.0%	Medium
0060	Permutation Sequence	Go	39.4%	Hard
0061	Rotate List	Go	31.8%	Medium
0062	Unique Paths	Go	56.1%	Medium
0063	Unique Paths II	Go	35.3%	Medium
0064	Minimum Path Sum	Go	56.3%	Medium
0065	Valid Number		15.9%	Hard
0066	Plus One	Go	42.3%	Easy
0067	Add Binary	Go	47.1%	Easy
0068	Text Justification		29.9%	Hard
0069	Sqrt(x)	Go	35.2%	Easy
0070	Climbing Stairs	Go	48.7%	Easy
0071	Simplify Path	Go	34.8%	Medium
0072	Edit Distance		46.9%	Hard
0073	Set Matrix Zeroes	Go	44.4%	Medium
0074	Search a 2D Matrix	Go	37.9%	Medium
0075	Sort Colors	Go	49.5%	Medium
0076	Minimum Window Substring	Go	36.1%	Hard
0077	Combinations	Go	57.6%	Medium
0078	Subsets	Go	65.3%	Medium
0079	Word Search	Go	36.9%	Medium
0080	Remove Duplicates from Sorted Array II	Go	46.2%	Medium
0081	Search in Rotated Sorted Array II	Go	33.6%	Medium
0082	Remove Duplicates from Sorted List II	Go	39.3%	Medium
0083	Remove Duplicates from Sorted List	Go	46.6%	Easy
0084	Largest Rectangle in Histogram	Go	37.2%	Hard
0085	Maximal Rectangle		39.6%	Hard
0086	Partition List	Go	43.5%	Medium
0087	Scramble String		34.8%	Hard
0088	Merge Sorted Array	Go	40.8%	Easy
0089	Gray Code	Go	50.5%	Medium
0090	Subsets II	Go	49.0%	Medium
0091	Decode Ways	Go	26.7%	Medium
0092	Reverse Linked List II	Go	40.7%	Medium
0093	Restore IP Addresses	Go	37.7%	Medium
0094	Binary Tree Inorder Traversal	Go	66.0%	Medium
0095	Unique Binary Search Trees II	Go	42.7%	Medium
0096	Unique Binary Search Trees	Go	54.5%	Medium
0097	Interleaving String		32.6%	Hard
0098	Validate Binary Search Tree	Go	28.8%	Medium
0099	Recover Binary Search Tree	Go	42.6%	Hard
0100	Same Tree	Go	54.2%	Easy
0101	Symmetric Tree	Go	48.2%	Easy
0102	Binary Tree Level Order Traversal	Go	56.8%	Medium
0103	Binary Tree Zigzag Level Order Traversal	Go	50.2%	Medium
0104	Maximum Depth of Binary Tree	Go	68.2%	Easy
0105	Construct Binary Tree from Preorder and Inorder Traversal	Go	52.0%	Medium
0106	Construct Binary Tree from Inorder and Postorder Traversal	Go	49.8%	Medium
0107	Binary Tree Level Order Traversal II	Go	55.3%	Medium
0108	Convert Sorted Array to Binary Search Tree	Go	60.6%	Easy
0109	Convert Sorted List to Binary Search Tree	Go	50.4%	Medium
0110	Balanced Binary Tree	Go	44.8%	Easy
0111	Minimum Depth of Binary Tree	Go	39.6%	Easy
0112	Path Sum	Go	42.5%	Easy
0113	Path Sum II	Go	49.2%	Medium
0114	Flatten Binary Tree to Linked List	Go	52.1%	Medium
0115	Distinct Subsequences		39.8%	Hard
0116	Populating Next Right Pointers in Each Node		49.3%	Medium
0117	Populating Next Right Pointers in Each Node II		42.2%	Medium
0118	Pascal's Triangle	Go	55.1%	Easy
0119	Pascal's Triangle II	Go	52.3%	Easy
0120	Triangle	Go	45.9%	Medium
0121	Best Time to Buy and Sell Stock	Go	51.7%	Easy
0122	Best Time to Buy and Sell Stock II	Go	58.6%	Easy
0123	Best Time to Buy and Sell Stock III		40.0%	Hard
0124	Binary Tree Maximum Path Sum	Go	35.5%	Hard
0125	Valid Palindrome	Go	38.3%	Easy
0126	Word Ladder II	Go	23.8%	Hard
0127	Word Ladder	Go	31.9%	Hard
0128	Longest Consecutive Sequence	Go	46.3%	Hard
0129	Sum Root to Leaf Numbers	Go	51.1%	Medium
0130	Surrounded Regions	Go	29.5%	Medium
0131	Palindrome Partitioning	Go	52.3%	Medium
0132	Palindrome Partitioning II		31.3%	Hard
0133	Clone Graph		39.4%	Medium
0134	Gas Station		41.4%	Medium
0135	Candy		33.2%	Hard
0136	Single Number	Go	66.6%	Easy
0137	Single Number II	Go	53.9%	Medium
0138	Copy List with Random Pointer	Go	41.1%	Medium
0139	Word Break		41.8%	Medium
0140	Word Break II		34.9%	Hard
0141	Linked List Cycle	Go	43.0%	Easy
0142	Linked List Cycle II	Go	39.8%	Medium
0143	Reorder List	Go	40.8%	Medium
0144	Binary Tree Preorder Traversal	Go	57.6%	Medium
0145	Binary Tree Postorder Traversal	Go	57.8%	Medium
0146	LRU Cache	Go	36.0%	Medium
0147	Insertion Sort List	Go	44.5%	Medium
0148	Sort List	Go	46.4%	Medium
0149	Max Points on a Line		17.5%	Hard
0150	Evaluate Reverse Polish Notation	Go	38.0%	Medium
0151	Reverse Words in a String	Go	23.9%	Medium
0152	Maximum Product Subarray	Go	32.8%	Medium
0153	Find Minimum in Rotated Sorted Array	Go	46.2%	Medium
0154	Find Minimum in Rotated Sorted Array II	Go	42.1%	Hard
0155	Min Stack	Go	46.6%	Easy
0156	Binary Tree Upside Down		56.5%	Medium
0157	Read N Characters Given Read4		37.4%	Easy
0158	Read N Characters Given Read4 II - Call multiple times		37.0%	Hard
0159	Longest Substring with At Most Two Distinct Characters		50.5%	Medium
0160	Intersection of Two Linked Lists	Go	44.2%	Easy
0161	One Edit Distance		33.1%	Medium
0162	Find Peak Element	Go	44.0%	Medium
0163	Missing Ranges		27.1%	Easy
0164	Maximum Gap	Go	36.9%	Hard
0165	Compare Version Numbers		30.5%	Medium
0166	Fraction to Recurring Decimal		22.3%	Medium
0167	Two Sum II - Input array is sorted	Go	55.7%	Easy
0168	Excel Sheet Column Title	Go	31.8%	Easy
0169	Majority Element	Go	60.1%	Easy
0170	Two Sum III - Data structure design		34.9%	Easy
0171	Excel Sheet Column Number	Go	57.0%	Easy
0172	Factorial Trailing Zeroes	Go	38.6%	Easy
0173	Binary Search Tree Iterator	Go	60.3%	Medium
0174	Dungeon Game	Go	33.3%	Hard
0175	Combine Two Tables		64.3%	Easy
0176	Second Highest Salary		33.3%	Easy
0177	Nth Highest Salary		33.4%	Medium
0178	Rank Scores		50.5%	Medium
0179	Largest Number	Go	30.7%	Medium
0180	Consecutive Numbers		42.3%	Medium
0181	Employees Earning More Than Their Managers		60.6%	Easy
0182	Duplicate Emails		64.8%	Easy
0183	Customers Who Never Order		57.1%	Easy
0184	Department Highest Salary		40.4%	Medium
0185	Department Top Three Salaries		39.3%	Hard
0186	Reverse Words in a String II		45.7%	Medium
0187	Repeated DNA Sequences	Go	41.5%	Medium
0188	Best Time to Buy and Sell Stock IV		29.8%	Hard
0189	Rotate Array	Go	36.7%	Medium
0190	Reverse Bits	Go	42.3%	Easy
0191	Number of 1 Bits	Go	54.0%	Easy
0192	Word Frequency		25.6%	Medium
0193	Valid Phone Numbers		25.4%	Easy
0194	Transpose File		24.4%	Medium
0195	Tenth Line		32.8%	Easy
0196	Delete Duplicate Emails		45.5%	Easy
0197	Rising Temperature		40.0%	Easy
0198	House Robber	Go	42.9%	Medium
0199	Binary Tree Right Side View	Go	56.4%	Medium
0200	Number of Islands	Go	49.3%	Medium
0201	Bitwise AND of Numbers Range	Go	39.6%	Medium
0202	Happy Number	Go	51.3%	Easy
0203	Remove Linked List Elements	Go	39.3%	Easy
0204	Count Primes	Go	32.3%	Easy
0205	Isomorphic Strings	Go	40.5%	Easy
0206	Reverse Linked List	Go	65.4%	Easy
0207	Course Schedule	Go	44.3%	Medium
0208	Implement Trie (Prefix Tree)	Go	52.3%	Medium
0209	Minimum Size Subarray Sum	Go	39.6%	Medium
0210	Course Schedule II	Go	42.7%	Medium
0211	Design Add and Search Words Data Structure	Go	40.3%	Medium
0212	Word Search II	Go	37.2%	Hard
0213	House Robber II	Go	37.6%	Medium
0214	Shortest Palindrome		30.7%	Hard
0215	Kth Largest Element in an Array	Go	58.6%	Medium
0216	Combination Sum III	Go	60.4%	Medium
0217	Contains Duplicate	Go	56.7%	Easy
0218	The Skyline Problem	Go	36.4%	Hard
0219	Contains Duplicate II	Go	38.7%	Easy
0220	Contains Duplicate III	Go	21.3%	Medium
0221	Maximal Square		39.3%	Medium
0222	Count Complete Tree Nodes	Go	49.4%	Medium
0223	Rectangle Area	Go	38.3%	Medium
0224	Basic Calculator	Go	38.2%	Hard
0225	Implement Stack using Queues	Go	47.6%	Easy
0226	Invert Binary Tree	Go	67.1%	Easy
0227	Basic Calculator II	Go	38.6%	Medium
0228	Summary Ranges	Go	42.5%	Easy
0229	Majority Element II	Go	38.9%	Medium
0230	Kth Smallest Element in a BST	Go	62.7%	Medium
0231	Power of Two	Go	43.8%	Easy
0232	Implement Queue using Stacks	Go	52.4%	Easy
0233	Number of Digit One		31.8%	Hard
0234	Palindrome Linked List	Go	40.7%	Easy
0235	Lowest Common Ancestor of a Binary Search Tree	Go	51.9%	Easy
0236	Lowest Common Ancestor of a Binary Tree	Go	49.0%	Medium
0237	Delete Node in a Linked List	Go	67.1%	Easy
0238	Product of Array Except Self		61.5%	Medium
0239	Sliding Window Maximum	Go	44.7%	Hard
0240	Search a 2D Matrix II	Go	45.2%	Medium
0241	Different Ways to Add Parentheses		57.4%	Medium
0242	Valid Anagram	Go	58.7%	Easy
0243	Shortest Word Distance		62.0%	Easy
0244	Shortest Word Distance II		54.2%	Medium
0245	Shortest Word Distance III		56.0%	Medium
0246	Strobogrammatic Number		46.3%	Easy
0247	Strobogrammatic Number II		48.6%	Medium
0248	Strobogrammatic Number III		40.3%	Hard
0249	Group Shifted Strings		58.3%	Medium
0250	Count Univalue Subtrees		53.4%	Medium
0251	Flatten 2D Vector		46.4%	Medium
0252	Meeting Rooms		55.4%	Easy
0253	Meeting Rooms II		46.9%	Medium
0254	Factor Combinations		47.5%	Medium
0255	Verify Preorder Sequence in Binary Search Tree		46.2%	Medium
0256	Paint House		53.7%	Medium
0257	Binary Tree Paths	Go	53.7%	Easy
0258	Add Digits	Go	58.6%	Easy
0259	3Sum Smaller		49.0%	Medium
0260	Single Number III	Go	65.4%	Medium
0261	Graph Valid Tree		43.3%	Medium
0262	Trips and Users		35.2%	Hard
0263	Ugly Number	Go	41.7%	Easy
0264	Ugly Number II		42.9%	Medium
0265	Paint House II		45.7%	Hard
0266	Palindrome Permutation		62.5%	Easy
0267	Palindrome Permutation II		37.4%	Medium
0268	Missing Number	Go	55.0%	Easy
0269	Alien Dictionary		33.7%	Hard
0270	Closest Binary Search Tree Value		50.0%	Easy
0271	Encode and Decode Strings		32.8%	Medium
0272	Closest Binary Search Tree Value II		52.4%	Hard
0273	Integer to English Words		28.2%	Hard
0274	H-Index	Go	36.4%	Medium
0275	H-Index II	Go	36.3%	Medium
0276	Paint Fence		39.1%	Medium
0277	Find the Celebrity		43.8%	Medium
0278	First Bad Version		37.6%	Easy
0279	Perfect Squares		49.0%	Medium
0280	Wiggle Sort		64.7%	Medium
0281	Zigzag Iterator		59.5%	Medium
0282	Expression Add Operators		36.8%	Hard
0283	Move Zeroes	Go	58.6%	Easy
0284	Peeking Iterator	Go	50.7%	Medium
0285	Inorder Successor in BST		43.0%	Medium
0286	Walls and Gates		56.7%	Medium
0287	Find the Duplicate Number	Go	57.7%	Medium
0288	Unique Word Abbreviation		23.1%	Medium
0289	Game of Life		58.5%	Medium
0290	Word Pattern	Go	38.4%	Easy
0291	Word Pattern II		44.3%	Medium
0292	Nim Game		55.1%	Easy
0293	Flip Game		61.4%	Easy
0294	Flip Game II		50.7%	Medium
0295	Find Median from Data Stream		47.1%	Hard
0296	Best Meeting Point		58.1%	Hard
0297	Serialize and Deserialize Binary Tree		49.9%	Hard
0298	Binary Tree Longest Consecutive Sequence		48.1%	Medium
0299	Bulls and Cows		44.6%	Medium
0300	Longest Increasing Subsequence	Go	44.2%	Medium
0301	Remove Invalid Parentheses		44.7%	Hard
0302	Smallest Rectangle Enclosing Black Pixels		52.5%	Hard
0303	Range Sum Query - Immutable	Go	47.8%	Easy
0304	Range Sum Query 2D - Immutable	Go	40.7%	Medium
0305	Number of Islands II		39.6%	Hard
0306	Additive Number	Go	29.7%	Medium
0307	Range Sum Query - Mutable	Go	36.8%	Medium
0308	Range Sum Query 2D - Mutable		37.8%	Hard
0309	Best Time to Buy and Sell Stock with Cooldown	Go	48.2%	Medium
0310	Minimum Height Trees		34.8%	Medium
0311	Sparse Matrix Multiplication		64.0%	Medium
0312	Burst Balloons		53.8%	Hard
0313	Super Ugly Number		46.2%	Medium
0314	Binary Tree Vertical Order Traversal		47.1%	Medium
0315	Count of Smaller Numbers After Self	Go	42.4%	Hard
0316	Remove Duplicate Letters		39.2%	Medium
0317	Shortest Distance from All Buildings		42.8%	Hard
0318	Maximum Product of Word Lengths	Go	52.3%	Medium
0319	Bulb Switcher		45.4%	Medium
0320	Generalized Abbreviation		53.8%	Medium
0321	Create Maximum Number		27.6%	Hard
0322	Coin Change	Go	37.6%	Medium
0323	Number of Connected Components in an Undirected Graph		57.9%	Medium
0324	Wiggle Sort II	Go	30.7%	Medium
0325	Maximum Size Subarray Sum Equals k		47.5%	Medium
0326	Power of Three	Go	42.1%	Easy
0327	Count of Range Sum	Go	36.1%	Hard
0328	Odd Even Linked List	Go	57.1%	Medium
0329	Longest Increasing Path in a Matrix	Go	45.1%	Hard
0330	Patching Array		35.0%	Hard
0331	Verify Preorder Serialization of a Binary Tree	Go	41.0%	Medium
0332	Reconstruct Itinerary		37.9%	Medium
0333	Largest BST Subtree		38.0%	Medium
0334	Increasing Triplet Subsequence		40.8%	Medium
0335	Self Crossing		28.7%	Hard
0336	Palindrome Pairs		34.7%	Hard
0337	House Robber III	Go	51.9%	Medium
0338	Counting Bits	Go	70.5%	Medium
0339	Nested List Weight Sum		76.6%	Medium
0340	Longest Substring with At Most K Distinct Characters		45.6%	Medium
0341	Flatten Nested List Iterator		54.6%	Medium
0342	Power of Four	Go	41.8%	Easy
0343	Integer Break	Go	51.2%	Medium
0344	Reverse String	Go	70.5%	Easy
0345	Reverse Vowels of a String	Go	45.1%	Easy
0346	Moving Average from Data Stream		73.4%	Easy
0347	Top K Frequent Elements	Go	62.5%	Medium
0348	Design Tic-Tac-Toe		55.6%	Medium
0349	Intersection of Two Arrays	Go	64.9%	Easy
0350	Intersection of Two Arrays II	Go	52.0%	Easy
0351	Android Unlock Patterns		49.7%	Medium
0352	Data Stream as Disjoint Intervals		48.7%	Hard
0353	Design Snake Game		36.0%	Medium
0354	Russian Doll Envelopes	Go	36.4%	Hard
0355	Design Twitter		31.5%	Medium
0356	Line Reflection		33.0%	Medium
0357	Count Numbers with Unique Digits	Go	48.9%	Medium
0358	Rearrange String k Distance Apart		35.7%	Hard
0359	Logger Rate Limiter		72.4%	Easy
0360	Sort Transformed Array		49.7%	Medium
0361	Bomb Enemy		46.7%	Medium
0362	Design Hit Counter		65.4%	Medium
0363	Max Sum of Rectangle No Larger Than K		38.4%	Hard
0364	Nested List Weight Sum II		63.8%	Medium
0365	Water and Jug Problem		31.1%	Medium
0366	Find Leaves of Binary Tree		71.9%	Medium
0367	Valid Perfect Square	Go	42.0%	Easy
0368	Largest Divisible Subset		38.3%	Medium
0369	Plus One Linked List		59.6%	Medium
0370	Range Addition		63.6%	Medium
0371	Sum of Two Integers	Go	50.6%	Medium
0372	Super Pow	Go	36.7%	Medium
0373	Find K Pairs with Smallest Sums	Go	37.8%	Medium
0374	Guess Number Higher or Lower		44.7%	Easy
0375	Guess Number Higher or Lower II		42.3%	Medium
0376	Wiggle Subsequence		40.3%	Medium
0377	Combination Sum IV		46.1%	Medium
0378	Kth Smallest Element in a Sorted Matrix	Go	56.3%	Medium
0379	Design Phone Directory		48.3%	Medium
0380	Insert Delete GetRandom O(1)		48.9%	Medium
0381	Insert Delete GetRandom O(1) - Duplicates allowed		34.9%	Hard
0382	Linked List Random Node		54.2%	Medium
0383	Ransom Note		53.3%	Easy
0384	Shuffle an Array		54.0%	Medium
0385	Mini Parser	Go	34.5%	Medium
0386	Lexicographical Numbers	Go	54.3%	Medium
0387	First Unique Character in a String	Go	53.8%	Easy
0388	Longest Absolute File Path		43.0%	Medium
0389	Find the Difference	Go	57.8%	Easy
0390	Elimination Game		45.0%	Medium
0391	Perfect Rectangle		31.2%	Hard
0392	Is Subsequence	Go	49.5%	Easy
0393	UTF-8 Validation	Go	38.1%	Medium
0394	Decode String	Go	52.8%	Medium
0395	Longest Substring with At Least K Repeating Characters	Go	43.6%	Medium
0396	Rotate Function		36.8%	Medium
0397	Integer Replacement	Go	33.5%	Medium
0398	Random Pick Index		58.1%	Medium
0399	Evaluate Division	Go	54.4%	Medium
0400	Nth Digit		32.4%	Medium
0401	Binary Watch	Go	48.5%	Easy
0402	Remove K Digits	Go	28.7%	Medium
0403	Frog Jump		41.5%	Hard
0404	Sum of Left Leaves	Go	52.3%	Easy
0405	Convert a Number to Hexadecimal	Go	44.5%	Easy
0406	Queue Reconstruction by Height		68.5%	Medium
0407	Trapping Rain Water II		44.3%	Hard
0408	Valid Word Abbreviation		31.4%	Easy
0409	Longest Palindrome	Go	52.2%	Easy
0410	Split Array Largest Sum	Go	46.5%	Hard
0411	Minimum Unique Word Abbreviation		37.3%	Hard
0412	Fizz Buzz	Go	63.6%	Easy
0413	Arithmetic Slices	Go	59.9%	Medium
0414	Third Maximum Number	Go	30.7%	Easy
0415	Add Strings		48.2%	Easy
0416	Partition Equal Subset Sum	Go	44.9%	Medium
0417	Pacific Atlantic Water Flow		42.6%	Medium
0418	Sentence Screen Fitting		33.3%	Medium
0419	Battleships in a Board		71.1%	Medium
0420	Strong Password Checker		14.0%	Hard
0421	Maximum XOR of Two Numbers in an Array	Go	54.2%	Medium
0422	Valid Word Square		38.2%	Easy
0423	Reconstruct Original Digits from English		47.5%	Medium
0424	Longest Repeating Character Replacement	Go	48.2%	Medium
0425	Word Squares		50.2%	Hard
0426	Convert Binary Search Tree to Sorted Doubly Linked List		61.3%	Medium
0427	Construct Quad Tree		62.7%	Medium
0428	Serialize and Deserialize N-ary Tree		61.6%	Hard
0429	N-ary Tree Level Order Traversal		66.8%	Medium
0430	Flatten a Multilevel Doubly Linked List		56.9%	Medium
0431	Encode N-ary Tree to Binary Tree		74.7%	Hard
0432	All O`one Data Structure		33.2%	Hard
0433	Minimum Genetic Mutation	Go	43.4%	Medium
0434	Number of Segments in a String		37.8%	Easy
0435	Non-overlapping Intervals	Go	43.9%	Medium
0436	Find Right Interval	Go	48.5%	Medium
0437	Path Sum III	Go	48.2%	Medium
0438	Find All Anagrams in a String	Go	45.0%	Medium
0439	Ternary Expression Parser		56.8%	Medium
0440	K-th Smallest in Lexicographical Order		29.8%	Hard
0441	Arranging Coins	Go	42.4%	Easy
0442	Find All Duplicates in an Array		69.0%	Medium
0443	String Compression		43.8%	Medium
0444	Sequence Reconstruction		23.6%	Medium
0445	Add Two Numbers II	Go	56.4%	Medium
0446	Arithmetic Slices II - Subsequence		33.5%	Hard
0447	Number of Boomerangs	Go	52.5%	Medium
0448	Find All Numbers Disappeared in an Array	Go	56.1%	Easy
0449	Serialize and Deserialize BST		54.1%	Medium
0450	Delete Node in a BST		45.4%	Medium
0451	Sort Characters By Frequency	Go	64.5%	Medium
0452	Minimum Number of Arrows to Burst Balloons		49.8%	Medium
0453	Minimum Moves to Equal Array Elements	Go	50.8%	Easy
0454	4Sum II	Go	54.6%	Medium
0455	Assign Cookies	Go	50.4%	Easy
0456	132 Pattern	Go	30.6%	Medium
0457	Circular Array Loop	Go	30.2%	Medium
0458	Poor Pigs		54.5%	Hard
0459	Repeated Substring Pattern		43.3%	Easy
0460	LFU Cache	Go	36.2%	Hard
0461	Hamming Distance	Go	73.2%	Easy
0462	Minimum Moves to Equal Array Elements II		54.4%	Medium
0463	Island Perimeter	Go	66.7%	Easy
0464	Can I Win		29.7%	Medium
0465	Optimal Account Balancing		48.3%	Hard
0466	Count The Repetitions		28.6%	Hard
0467	Unique Substrings in Wraparound String		36.1%	Medium
0468	Validate IP Address		25.0%	Medium
0469	Convex Polygon		37.5%	Medium
0470	Implement Rand10() Using Rand7()	Go	46.1%	Medium
0471	Encode String with Shortest Length		49.3%	Hard
0472	Concatenated Words		43.9%	Hard
0473	Matchsticks to Square		38.2%	Medium
0474	Ones and Zeroes	Go	43.7%	Medium
0475	Heaters	Go	33.7%	Medium
0476	Number Complement	Go	65.2%	Easy
0477	Total Hamming Distance	Go	50.6%	Medium
0478	Generate Random Point in a Circle		38.9%	Medium
0479	Largest Palindrome Product		29.6%	Hard
0480	Sliding Window Median	Go	38.8%	Hard
0481	Magical String		48.1%	Medium
0482	License Key Formatting		43.1%	Easy
0483	Smallest Good Base	Go	36.3%	Hard
0484	Find Permutation		64.2%	Medium
0485	Max Consecutive Ones	Go	52.8%	Easy
0486	Predict the Winner		48.9%	Medium
0487	Max Consecutive Ones II		48.0%	Medium
0488	Zuma Game		38.2%	Hard
0489	Robot Room Cleaner		72.7%	Hard
0490	The Maze		52.8%	Medium
0491	Increasing Subsequences	Go	47.6%	Medium
0492	Construct the Rectangle		50.5%	Easy
0493	Reverse Pairs	Go	26.9%	Hard
0494	Target Sum	Go	45.7%	Medium
0495	Teemo Attacking		56.1%	Medium
0496	Next Greater Element I	Go	65.7%	Easy
0497	Random Point in Non-overlapping Rectangles	Go	39.1%	Medium
0498	Diagonal Traverse	Go	50.4%	Medium
0499	The Maze III		42.5%	Hard
0500	Keyboard Row	Go	65.7%	Easy
0501	Find Mode in Binary Search Tree		43.6%	Easy
0502	IPO		41.7%	Hard
0503	Next Greater Element II	Go	58.5%	Medium
0504	Base 7		46.4%	Easy
0505	The Maze II		48.6%	Medium
0506	Relative Ranks		51.3%	Easy
0507	Perfect Number	Go	36.2%	Easy
0508	Most Frequent Subtree Sum	Go	59.1%	Medium
0509	Fibonacci Number	Go	67.5%	Easy
0510	Inorder Successor in BST II		60.1%	Medium
0511	Game Play Analysis I		81.4%	Easy
0512	Game Play Analysis II		56.1%	Easy
0513	Find Bottom Left Tree Value	Go	62.7%	Medium
0514	Freedom Trail		45.0%	Hard
0515	Find Largest Value in Each Tree Row	Go	62.3%	Medium
0516	Longest Palindromic Subsequence		55.6%	Medium
0517	Super Washing Machines		38.6%	Hard
0518	Coin Change 2		51.9%	Medium
0519	Random Flip Matrix		37.8%	Medium
0520	Detect Capital		53.9%	Easy
0521	Longest Uncommon Subsequence I		58.8%	Easy
0522	Longest Uncommon Subsequence II		34.2%	Medium
0523	Continuous Subarray Sum		24.7%	Medium
0524	Longest Word in Dictionary through Deleting	Go	50.1%	Medium
0525	Contiguous Array		43.5%	Medium
0526	Beautiful Arrangement	Go	61.9%	Medium
0527	Word Abbreviation		56.3%	Hard
0528	Random Pick with Weight	Go	44.7%	Medium
0529	Minesweeper	Go	61.2%	Medium
0530	Minimum Absolute Difference in BST		54.9%	Easy
0531	Lonely Pixel I		59.6%	Medium
0532	K-diff Pairs in an Array	Go	35.3%	Medium
0533	Lonely Pixel II		48.2%	Medium
0534	Game Play Analysis III		79.5%	Medium
0535	Encode and Decode TinyURL		81.0%	Medium
0536	Construct Binary Tree from String		50.8%	Medium
0537	Complex Number Multiplication	Go	68.3%	Medium
0538	Convert BST to Greater Tree	Go	59.6%	Medium
0539	Minimum Time Difference		52.4%	Medium
0540	Single Element in a Sorted Array		57.9%	Medium
0541	Reverse String II	Go	49.2%	Easy
0542	01 Matrix	Go	41.0%	Medium
0543	Diameter of Binary Tree		49.2%	Easy
0544	Output Contest Matches		75.8%	Medium
0545	Boundary of Binary Tree		40.0%	Medium
0546	Remove Boxes		44.1%	Hard
0547	Number of Provinces	Go	60.6%	Medium
0548	Split Array with Equal Sum		48.0%	Medium
0549	Binary Tree Longest Consecutive Sequence II		47.3%	Medium
0550	Game Play Analysis IV		45.6%	Medium
0551	Student Attendance Record I		46.0%	Easy
0552	Student Attendance Record II		37.5%	Hard
0553	Optimal Division		57.5%	Medium
0554	Brick Wall		50.7%	Medium
0555	Split Concatenated Strings		42.8%	Medium
0556	Next Greater Element III		33.5%	Medium
0557	Reverse Words in a String III	Go	72.1%	Easy
0558	Logical OR of Two Binary Grids Represented as Quad-Trees		45.6%	Medium
0559	Maximum Depth of N-ary Tree		69.6%	Easy
0560	Subarray Sum Equals K		43.7%	Medium
0561	Array Partition I	Go	73.3%	Easy
0562	Longest Line of Consecutive One in Matrix		46.2%	Medium
0563	Binary Tree Tilt	Go	53.1%	Easy
0564	Find the Closest Palindrome		20.3%	Hard
0565	Array Nesting		56.0%	Medium
0566	Reshape the Matrix	Go	61.1%	Easy
0567	Permutation in String	Go	44.6%	Medium
0568	Maximum Vacation Days		41.6%	Hard
0569	Median Employee Salary		61.9%	Hard
0570	Managers with at Least 5 Direct Reports		66.9%	Medium
0571	Find Median Given Frequency of Numbers		45.5%	Hard
0572	Subtree of Another Tree	Go	44.5%	Easy
0573	Squirrel Simulation		54.1%	Medium
0574	Winning Candidate		52.3%	Medium
0575	Distribute Candies	Go	64.6%	Easy
0576	Out of Boundary Paths		36.0%	Medium
0577	Employee Bonus		71.7%	Easy
0578	Get Highest Answer Rate Question		41.8%	Medium
0579	Find Cumulative Salary of an Employee		38.5%	Hard
0580	Count Student Number in Departments		51.9%	Medium
0581	Shortest Unsorted Continuous Subarray	Go	32.8%	Medium
0582	Kill Process		63.8%	Medium
0583	Delete Operation for Two Strings		50.1%	Medium
0584	Find Customer Referee		74.1%	Easy
0585	Investments in 2016		57.1%	Medium
0586	Customer Placing the Largest Number of Orders		75.4%	Easy
0587	Erect the Fence		36.5%	Hard
0588	Design In-Memory File System		46.7%	Hard
0589	N-ary Tree Preorder Traversal		73.4%	Easy
0590	N-ary Tree Postorder Traversal		73.4%	Easy
0591	Tag Validator		34.7%	Hard
0592	Fraction Addition and Subtraction		50.2%	Medium
0593	Valid Square		43.3%	Medium
0594	Longest Harmonious Subsequence	Go	51.2%	Easy
0595	Big Countries		78.5%	Easy
0596	Classes More Than 5 Students		38.9%	Easy
0597	Friend Requests I: Overall Acceptance Rate		41.9%	Easy
0598	Range Addition II	Go	50.2%	Easy
0599	Minimum Index Sum of Two Lists	Go	51.8%	Easy
0600	Non-negative Integers without Consecutive Ones		34.7%	Hard
0601	Human Traffic of Stadium		45.3%	Hard
0602	Friend Requests II: Who Has the Most Friends		57.5%	Medium
0603	Consecutive Available Seats		66.1%	Easy
0604	Design Compressed String Iterator		38.2%	Easy
0605	Can Place Flowers	Go	31.8%	Easy
0606	Construct String from Binary Tree		55.3%	Easy
0607	Sales Person		65.2%	Easy
0608	Tree Node		69.8%	Medium
0609	Find Duplicate File in System		61.1%	Medium
0610	Triangle Judgement		68.6%	Easy
0611	Valid Triangle Number		49.4%	Medium
0612	Shortest Distance in a Plane		61.4%	Medium
0613	Shortest Distance in a Line		79.7%	Easy
0614	Second Degree Follower		32.6%	Medium
0615	Average Salary: Departments VS Company		52.7%	Hard
0616	Add Bold Tag in String		44.8%	Medium
0617	Merge Two Binary Trees		75.4%	Easy
0618	Students Report By Geography		60.2%	Hard
0619	Biggest Single Number		45.0%	Easy
0620	Not Boring Movies		70.0%	Easy
0621	Task Scheduler		52.0%	Medium
0622	Design Circular Queue		45.9%	Medium
0623	Add One Row to Tree	Go	53.1%	Medium
0624	Maximum Distance in Arrays		39.6%	Medium
0625	Minimum Factorization		32.9%	Medium
0626	Exchange Seats		65.8%	Medium
0627	Swap Salary		77.8%	Easy
0628	Maximum Product of Three Numbers	Go	46.8%	Easy
0629	K Inverse Pairs Array		31.7%	Hard
0630	Course Schedule III		33.8%	Hard
0631	Design Excel Sum Formula		32.1%	Hard
0632	Smallest Range Covering Elements from K Lists	Go	54.3%	Hard
0633	Sum of Square Numbers	Go	32.6%	Medium
0634	Find the Derangement of An Array		40.6%	Medium
0635	Design Log Storage System		59.9%	Medium
0636	Exclusive Time of Functions	Go	54.7%	Medium
0637	Average of Levels in Binary Tree	Go	66.0%	Easy
0638	Shopping Offers	Go	53.0%	Medium
0639	Decode Ways II		27.6%	Hard
0640	Solve the Equation		42.8%	Medium
0641	Design Circular Deque		56.2%	Medium
0642	Design Search Autocomplete System		46.3%	Hard
0643	Maximum Average Subarray I	Go	42.0%	Easy
0644	Maximum Average Subarray II		34.1%	Hard
0645	Set Mismatch	Go	41.9%	Easy
0646	Maximum Length of Pair Chain		53.0%	Medium
0647	Palindromic Substrings		61.9%	Medium
0648	Replace Words	Go	58.7%	Medium
0649	Dota2 Senate		39.4%	Medium
0650	2 Keys Keyboard		50.1%	Medium
0651	4 Keys Keyboard		53.2%	Medium
0652	Find Duplicate Subtrees		52.6%	Medium
0653	Two Sum IV - Input is a BST	Go	56.3%	Easy
0654	Maximum Binary Tree		81.2%	Medium
0655	Print Binary Tree		56.2%	Medium
0656	Coin Path		29.7%	Hard
0657	Robot Return to Origin		73.9%	Easy
0658	Find K Closest Elements	Go	42.1%	Medium
0659	Split Array into Consecutive Subsequences		44.4%	Medium
0660	Remove 9		54.2%	Hard
0661	Image Smoother	Go	52.3%	Easy
0662	Maximum Width of Binary Tree	Go	39.8%	Medium
0663	Equal Tree Partition		39.8%	Medium
0664	Strange Printer		41.5%	Hard
0665	Non-decreasing Array	Go	19.8%	Medium
0666	Path Sum IV		56.4%	Medium
0667	Beautiful Arrangement II		55.2%	Medium
0668	Kth Smallest Number in Multiplication Table	Go	47.8%	Hard
0669	Trim a Binary Search Tree	Go	64.4%	Medium
0670	Maximum Swap		45.2%	Medium
0671	Second Minimum Node In a Binary Tree		42.8%	Easy
0672	Bulb Switcher II		51.1%	Medium
0673	Number of Longest Increasing Subsequence		38.5%	Medium
0674	Longest Continuous Increasing Subsequence	Go	46.0%	Easy
0675	Cut Off Trees for Golf Event		35.4%	Hard
0676	Implement Magic Dictionary	Go	55.3%	Medium
0677	Map Sum Pairs		54.0%	Medium
0678	Valid Parenthesis String		31.7%	Medium
0679	24 Game		47.2%	Hard
0680	Valid Palindrome II		37.1%	Easy
0681	Next Closest Time		45.9%	Medium
0682	Baseball Game	Go	67.2%	Easy
0683	K Empty Slots		36.1%	Hard
0684	Redundant Connection	Go	59.0%	Medium
0685	Redundant Connection II	Go	33.0%	Hard
0686	Repeated String Match		32.9%	Medium
0687	Longest Univalue Path		37.3%	Medium
0688	Knight Probability in Chessboard		50.2%	Medium
0689	Maximum Sum of 3 Non-Overlapping Subarrays		47.2%	Hard
0690	Employee Importance		58.8%	Easy
0691	Stickers to Spell Word		44.8%	Hard
0692	Top K Frequent Words		53.1%	Medium
0693	Binary Number with Alternating Bits	Go	59.9%	Easy
0694	Number of Distinct Islands		57.9%	Medium
0695	Max Area of Island	Go	64.9%	Medium
0696	Count Binary Substrings		57.8%	Easy
0697	Degree of an Array	Go	54.5%	Easy
0698	Partition to K Equal Sum Subsets		45.7%	Medium
0699	Falling Squares	Go	42.6%	Hard
0700	Search in a Binary Search Tree		73.4%	Easy
0701	Insert into a Binary Search Tree		75.5%	Medium
0702	Search in a Sorted Array of Unknown Size		68.9%	Medium
0703	Kth Largest Element in a Stream	Go	50.8%	Easy
0704	Binary Search	Go	54.1%	Easy
0705	Design HashSet	Go	64.6%	Easy
0706	Design HashMap	Go	64.2%	Easy
0707	Design Linked List	Go	25.9%	Medium
0708	Insert into a Sorted Circular Linked List		32.6%	Medium
0709	To Lower Case		80.2%	Easy
0710	Random Pick with Blacklist	Go	33.0%	Hard
0711	Number of Distinct Islands II		49.3%	Hard
0712	Minimum ASCII Delete Sum for Two Strings		59.5%	Medium
0713	Subarray Product Less Than K	Go	40.5%	Medium
0714	Best Time to Buy and Sell Stock with Transaction Fee	Go	56.2%	Medium
0715	Range Module	Go	40.3%	Hard
0716	Max Stack		43.1%	Easy
0717	1-bit and 2-bit Characters	Go	47.1%	Easy
0718	Maximum Length of Repeated Subarray	Go	50.4%	Medium
0719	Find K-th Smallest Pair Distance	Go	32.6%	Hard
0720	Longest Word in Dictionary	Go	49.3%	Easy
0721	Accounts Merge	Go	52.0%	Medium
0722	Remove Comments		36.2%	Medium
0723	Candy Crush		72.8%	Medium
0724	Find Pivot Index	Go	45.7%	Easy
0725	Split Linked List in Parts	Go	53.0%	Medium
0726	Number of Atoms	Go	51.0%	Hard
0727	Minimum Window Subsequence		42.2%	Hard
0728	Self Dividing Numbers		75.5%	Easy
0729	My Calendar I	Go	53.5%	Medium
0730	Count Different Palindromic Subsequences		43.4%	Hard
0731	My Calendar II		50.7%	Medium
0732	My Calendar III	Go	62.1%	Hard
0733	Flood Fill	Go	55.9%	Easy
0734	Sentence Similarity		42.4%	Easy
0735	Asteroid Collision	Go	43.2%	Medium
0736	Parse Lisp Expression		49.7%	Hard
0737	Sentence Similarity II		46.6%	Medium
0738	Monotone Increasing Digits		45.7%	Medium
0739	Daily Temperatures	Go	64.7%	Medium
0740	Delete and Earn		49.5%	Medium
0741	Cherry Pickup		35.1%	Hard
0742	Closest Leaf in a Binary Tree		44.5%	Medium
0743	Network Delay Time		45.6%	Medium
0744	Find Smallest Letter Greater Than Target	Go	45.6%	Easy
0745	Prefix and Suffix Search	Go	35.4%	Hard
0746	Min Cost Climbing Stairs	Go	50.9%	Easy
0747	Largest Number At Least Twice of Others		43.1%	Easy
0748	Shortest Completing Word	Go	57.5%	Easy
0749	Contain Virus		48.2%	Hard
0750	Number Of Corner Rectangles		67.2%	Medium
0751	IP to CIDR		59.5%	Medium
0752	Open the Lock		52.9%	Medium
0753	Cracking the Safe	Go	52.4%	Hard
0754	Reach a Number		40.5%	Medium
0755	Pour Water		44.1%	Medium
0756	Pyramid Transition Matrix	Go	55.6%	Medium
0757	Set Intersection Size At Least Two		42.6%	Hard
0758	Bold Words in String		47.4%	Easy
0759	Employee Free Time		68.3%	Hard
0760	Find Anagram Mappings		81.9%	Easy
0761	Special Binary String		58.7%	Hard
0762	Prime Number of Set Bits in Binary Representation	Go	64.4%	Easy
0763	Partition Labels	Go	78.1%	Medium
0764	Largest Plus Sign		46.6%	Medium
0765	Couples Holding Hands	Go	55.5%	Hard
0766	Toeplitz Matrix	Go	65.9%	Easy
0767	Reorganize String	Go	50.2%	Medium
0768	Max Chunks To Make Sorted II		49.8%	Hard
0769	Max Chunks To Make Sorted		55.7%	Medium
0770	Basic Calculator IV		54.2%	Hard
0771	Jewels and Stones	Go	86.9%	Easy
0772	Basic Calculator III		43.8%	Hard
0773	Sliding Puzzle		61.0%	Hard
0774	Minimize Max Distance to Gas Station		48.3%	Hard
0775	Global and Local Inversions		42.6%	Medium
0776	Split BST		56.6%	Medium
0777	Swap Adjacent in LR String		35.7%	Medium
0778	Swim in Rising Water	Go	54.7%	Hard
0779	K-th Symbol in Grammar		38.6%	Medium
0780	Reaching Points		30.4%	Hard
0781	Rabbits in Forest	Go	55.6%	Medium
0782	Transform to Chessboard		47.0%	Hard
0783	Minimum Distance Between BST Nodes		53.9%	Easy
0784	Letter Case Permutation	Go	68.6%	Medium
0785	Is Graph Bipartite?	Go	48.7%	Medium
0786	K-th Smallest Prime Fraction	Go	42.9%	Hard
0787	Cheapest Flights Within K Stops		39.6%	Medium
0788	Rotated Digits		57.2%	Easy
0789	Escape The Ghosts		58.4%	Medium
0790	Domino and Tromino Tiling		40.2%	Medium
0791	Custom Sort String		65.9%	Medium
0792	Number of Matching Subsequences		48.2%	Medium
0793	Preimage Size of Factorial Zeroes Function	Go	40.6%	Hard
0794	Valid Tic-Tac-Toe State		33.7%	Medium
0795	Number of Subarrays with Bounded Maximum		47.7%	Medium
0796	Rotate String		49.2%	Easy
0797	All Paths From Source to Target		78.5%	Medium
0798	Smallest Rotation with Highest Score		45.0%	Hard
0799	Champagne Tower		44.1%	Medium
0800	Similar RGB Color		62.4%	Easy
0801	Minimum Swaps To Make Sequences Increasing		39.0%	Medium
0802	Find Eventual Safe States	Go	49.9%	Medium
0803	Bricks Falling When Hit	Go	31.5%	Hard
0804	Unique Morse Code Words		79.0%	Easy
0805	Split Array With Same Average		26.9%	Hard
0806	Number of Lines To Write String		65.5%	Easy
0807	Max Increase to Keep City Skyline		84.4%	Medium
0808	Soup Servings		41.0%	Medium
0809	Expressive Words		46.4%	Medium
0810	Chalkboard XOR Game		49.7%	Hard
0811	Subdomain Visit Count	Go	71.6%	Easy
0812	Largest Triangle Area	Go	59.0%	Easy
0813	Largest Sum of Averages		51.1%	Medium
0814	Binary Tree Pruning		72.3%	Medium
0815	Bus Routes	Go	43.4%	Hard
0816	Ambiguous Coordinates		48.0%	Medium
0817	Linked List Components	Go	57.8%	Medium
0818	Race Car		40.0%	Hard
0819	Most Common Word	Go	45.5%	Easy
0820	Short Encoding of Words	Go	55.2%	Medium
0821	Shortest Distance to a Character	Go	70.1%	Easy
0822	Card Flipping Game		43.7%	Medium
0823	Binary Trees With Factors	Go	43.9%	Medium
0824	Goat Latin		66.6%	Easy
0825	Friends Of Appropriate Ages		44.2%	Medium
0826	Most Profit Assigning Work	Go	39.2%	Medium
0827	Making A Large Island		47.4%	Hard
0828	Count Unique Characters of All Substrings of a Given String	Go	46.8%	Hard
0829	Consecutive Numbers Sum		39.3%	Hard
0830	Positions of Large Groups	Go	50.4%	Easy
0831	Masking Personal Information		44.8%	Medium
0832	Flipping an Image	Go	78.2%	Easy
0833	Find And Replace in String		51.5%	Medium
0834	Sum of Distances in Tree	Go	46.2%	Hard
0835	Image Overlap		61.7%	Medium
0836	Rectangle Overlap	Go	44.1%	Easy
0837	New 21 Game		35.4%	Medium
0838	Push Dominoes	Go	49.9%	Medium
0839	Similar String Groups	Go	41.1%	Hard
0840	Magic Squares In Grid		37.9%	Medium
0841	Keys and Rooms	Go	65.5%	Medium
0842	Split Array into Fibonacci Sequence	Go	37.0%	Medium
0843	Guess the Word		46.5%	Hard
0844	Backspace String Compare	Go	47.1%	Easy
0845	Longest Mountain in Array	Go	38.6%	Medium
0846	Hand of Straights		55.4%	Medium
0847	Shortest Path Visiting All Nodes		53.9%	Hard
0848	Shifting Letters		45.2%	Medium
0849	Maximize Distance to Closest Person		44.5%	Medium
0850	Rectangle Area II	Go	48.3%	Hard
0851	Loud and Rich	Go	52.7%	Medium
0852	Peak Index in a Mountain Array	Go	71.7%	Easy
0853	Car Fleet	Go	44.1%	Medium
0854	K-Similar Strings		38.7%	Hard
0855	Exam Room		43.4%	Medium
0856	Score of Parentheses	Go	64.8%	Medium
0857	Minimum Cost to Hire K Workers		50.4%	Hard
0858	Mirror Reflection		59.6%	Medium
0859	Buddy Strings		29.3%	Easy
0860	Lemonade Change		51.8%	Easy
0861	Score After Flipping Matrix		73.7%	Medium
0862	Shortest Subarray with Sum at Least K	Go	25.2%	Hard
0863	All Nodes Distance K in Binary Tree	Go	58.0%	Medium
0864	Shortest Path to Get All Keys	Go	42.1%	Hard
0865	Smallest Subtree with all the Deepest Nodes		64.9%	Medium
0866	Prime Palindrome		25.1%	Medium
0867	Transpose Matrix	Go	62.0%	Easy
0868	Binary Gap		61.0%	Easy
0869	Reordered Power of 2		54.3%	Medium
0870	Advantage Shuffle		46.9%	Medium
0871	Minimum Number of Refueling Stops		32.4%	Hard
0872	Leaf-Similar Trees	Go	64.5%	Easy
0873	Length of Longest Fibonacci Subsequence		48.2%	Medium
0874	Walking Robot Simulation		36.8%	Easy
0875	Koko Eating Bananas	Go	53.5%	Medium
0876	Middle of the Linked List	Go	69.2%	Easy
0877	Stone Game		66.9%	Medium
0878	Nth Magical Number	Go	28.8%	Hard
0879	Profitable Schemes		40.0%	Hard
0880	Decoded String at Index	Go	28.2%	Medium
0881	Boats to Save People	Go	49.0%	Medium
0882	Reachable Nodes In Subdivided Graph		43.0%	Hard
0883	Projection Area of 3D Shapes		68.3%	Easy
0884	Uncommon Words from Two Sentences	Go	64.2%	Easy
0885	Spiral Matrix III	Go	70.9%	Medium
0886	Possible Bipartition		45.2%	Medium
0887	Super Egg Drop	Go	27.0%	Hard
0888	Fair Candy Swap	Go	59.1%	Easy
0889	Construct Binary Tree from Preorder and Postorder Traversal		67.7%	Medium
0890	Find and Replace Pattern		74.2%	Medium
0891	Sum of Subsequence Widths	Go	33.1%	Hard
0892	Surface Area of 3D Shapes	Go	59.8%	Easy
0893	Groups of Special-Equivalent Strings		69.3%	Easy
0894	All Possible Full Binary Trees		77.1%	Medium
0895	Maximum Frequency Stack	Go	63.1%	Hard
0896	Monotonic Array	Go	58.0%	Easy
0897	Increasing Order Search Tree	Go	74.6%	Easy
0898	Bitwise ORs of Subarrays	Go	34.3%	Medium
0899	Orderly Queue		53.2%	Hard
0900	RLE Iterator		55.5%	Medium
0901	Online Stock Span	Go	61.4%	Medium
0902	Numbers At Most N Given Digit Set		36.1%	Hard
0903	Valid Permutations for DI Sequence		54.1%	Hard
0904	Fruit Into Baskets	Go	43.0%	Medium
0905	Sort Array By Parity		75.0%	Easy
0906	Super Palindromes		32.8%	Hard
0907	Sum of Subarray Minimums	Go	33.1%	Medium
0908	Smallest Range I		66.4%	Easy
0909	Snakes and Ladders		39.3%	Medium
0910	Smallest Range II	Go	31.2%	Medium
0911	Online Election	Go	51.4%	Medium
0912	Sort an Array		64.6%	Medium
0913	Cat and Mouse		34.8%	Hard
0914	X of a Kind in a Deck of Cards	Go	34.2%	Easy
0915	Partition Array into Disjoint Intervals		46.2%	Medium
0916	Word Subsets		48.1%	Medium
0917	Reverse Only Letters		59.0%	Easy
0918	Maximum Sum Circular Subarray	Go	34.2%	Medium
0919	Complete Binary Tree Inserter		58.9%	Medium
0920	Number of Music Playlists	Go	47.8%	Hard
0921	Minimum Add to Make Parentheses Valid	Go	74.9%	Medium
0922	Sort Array By Parity II	Go	70.6%	Easy
0923	3Sum With Multiplicity	Go	36.3%	Medium
0924	Minimize Malware Spread	Go	41.9%	Hard
0925	Long Pressed Name	Go	37.7%	Easy
0926	Flip String to Monotone Increasing		53.3%	Medium
0927	Three Equal Parts	Go	34.6%	Hard
0928	Minimize Malware Spread II	Go	41.5%	Hard
0929	Unique Email Addresses		67.2%	Easy
0930	Binary Subarrays With Sum	Go	44.6%	Medium
0931	Minimum Falling Path Sum		63.6%	Medium
0932	Beautiful Array		61.4%	Medium
0933	Number of Recent Calls	Go	72.4%	Easy
0934	Shortest Bridge		49.7%	Medium
0935	Knight Dialer		46.6%	Medium
0936	Stamping The Sequence		47.5%	Hard
0937	Reorder Data in Log Files		54.5%	Easy
0938	Range Sum of BST		83.1%	Easy
0939	Minimum Area Rectangle		52.0%	Medium
0940	Distinct Subsequences II		41.6%	Hard
0941	Valid Mountain Array		33.2%	Easy
0942	DI String Match	Go	73.6%	Easy
0943	Find the Shortest Superstring		43.4%	Hard
0944	Delete Columns to Make Sorted		70.9%	Easy
0945	Minimum Increment to Make Array Unique		46.8%	Medium
0946	Validate Stack Sequences	Go	64.4%	Medium
0947	Most Stones Removed with Same Row or Column	Go	55.5%	Medium
0948	Bag of Tokens		46.1%	Medium
0949	Largest Time for Given Digits	Go	36.2%	Medium
0950	Reveal Cards In Increasing Order		75.4%	Medium
0951	Flip Equivalent Binary Trees		65.8%	Medium
0952	Largest Component Size by Common Factor	Go	36.2%	Hard
0953	Verifying an Alien Dictionary	Go	52.0%	Easy
0954	Array of Doubled Pairs		35.1%	Medium
0955	Delete Columns to Make Sorted II		33.8%	Medium
0956	Tallest Billboard		39.8%	Hard
0957	Prison Cells After N Days		40.1%	Medium
0958	Check Completeness of a Binary Tree		52.5%	Medium
0959	Regions Cut By Slashes	Go	67.2%	Medium
0960	Delete Columns to Make Sorted III		54.9%	Hard
0961	N-Repeated Element in Size 2N Array	Go	74.5%	Easy
0962	Maximum Width Ramp		46.6%	Medium
0963	Minimum Area Rectangle II		52.0%	Medium
0964	Least Operators to Express Number		45.1%	Hard
0965	Univalued Binary Tree		67.9%	Easy
0966	Vowel Spellchecker		47.9%	Medium
0967	Numbers With Same Consecutive Differences		44.9%	Medium
0968	Binary Tree Cameras	Go	38.9%	Hard
0969	Pancake Sorting	Go	68.7%	Medium
0970	Powerful Integers	Go	40.0%	Medium
0971	Flip Binary Tree To Match Preorder Traversal		46.1%	Medium
0972	Equal Rational Numbers		42.1%	Hard
0973	K Closest Points to Origin	Go	64.6%	Medium
0974	Subarray Sums Divisible by K		50.9%	Medium
0975	Odd Even Jump		41.5%	Hard
0976	Largest Perimeter Triangle	Go	58.6%	Easy
0977	Squares of a Sorted Array	Go	71.9%	Easy
0978	Longest Turbulent Subarray	Go	46.6%	Medium
0979	Distribute Coins in Binary Tree	Go	69.8%	Medium
0980	Unique Paths III	Go	77.1%	Hard
0981	Time Based Key-Value Store	Go	54.1%	Medium
0982	Triples with Bitwise AND Equal To Zero		56.3%	Hard
0983	Minimum Cost For Tickets		62.8%	Medium
0984	String Without AAA or BBB	Go	38.7%	Medium
0985	Sum of Even Numbers After Queries	Go	60.7%	Easy
0986	Interval List Intersections	Go	68.4%	Medium
0987	Vertical Order Traversal of a Binary Tree	Go	38.9%	Hard
0988	Smallest String Starting From Leaf		46.7%	Medium
0989	Add to Array-Form of Integer	Go	44.9%	Easy
0990	Satisfiability of Equality Equations	Go	46.9%	Medium
0991	Broken Calculator	Go	49.7%	Medium
0992	Subarrays with K Different Integers	Go	50.7%	Hard
0993	Cousins in Binary Tree	Go	52.3%	Easy
0994	Rotting Oranges		49.6%	Medium
0995	Minimum Number of K Consecutive Bit Flips	Go	49.9%	Hard
0996	Number of Squareful Arrays	Go	48.5%	Hard
0997	Find the Town Judge		49.8%	Easy
0998	Maximum Binary Tree II		64.0%	Medium
0999	Available Captures for Rook	Go	67.8%	Easy
1000	Minimum Cost to Merge Stones		40.5%	Hard
1001	Grid Illumination		36.4%	Hard
1002	Find Common Characters	Go	68.6%	Easy
1003	Check If Word Is Valid After Substitutions	Go	56.5%	Medium
1004	Max Consecutive Ones III	Go	60.9%	Medium
1005	Maximize Sum Of Array After K Negations	Go	52.3%	Easy
1006	Clumsy Factorial		53.5%	Medium
1007	Minimum Domino Rotations For Equal Row		50.9%	Medium
1008	Construct Binary Search Tree from Preorder Traversal		78.8%	Medium
1009	Complement of Base 10 Integer		61.5%	Easy
1010	Pairs of Songs With Total Durations Divisible by 60		50.4%	Medium
1011	Capacity To Ship Packages Within D Days	Go	59.7%	Medium
1012	Numbers With Repeated Digits		37.8%	Hard
1013	Partition Array Into Three Parts With Equal Sum		48.6%	Easy
1014	Best Sightseeing Pair		52.9%	Medium
1015	Smallest Integer Divisible by K		41.8%	Medium
1016	Binary String With Substrings Representing 1 To N		58.8%	Medium
1017	Convert to Base -2	Go	59.8%	Medium
1018	Binary Prefix Divisible By 5	Go	47.8%	Easy
1019	Next Greater Node In Linked List	Go	58.3%	Medium
1020	Number of Enclaves	Go	59.1%	Medium
1021	Remove Outermost Parentheses	Go	79.1%	Easy
1022	Sum of Root To Leaf Binary Numbers		71.5%	Easy
1023	Camelcase Matching		57.6%	Medium
1024	Video Stitching		49.0%	Medium
1025	Divisor Game	Go	66.1%	Easy
1026	Maximum Difference Between Node and Ancestor	Go	69.6%	Medium
1027	Longest Arithmetic Subsequence		49.8%	Medium
1028	Recover a Tree From Preorder Traversal	Go	70.9%	Hard
1029	Two City Scheduling		58.1%	Medium
1030	Matrix Cells in Distance Order	Go	67.1%	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays		59.0%	Medium
1032	Stream of Characters		48.6%	Hard
1033	Moving Stones Until Consecutive		43.2%	Easy
1034	Coloring A Border		45.7%	Medium
1035	Uncrossed Lines		56.1%	Medium
1036	Escape a Large Maze		34.4%	Hard
1037	Valid Boomerang	Go	37.8%	Easy
1038	Binary Search Tree to Greater Sum Tree	Go	82.4%	Medium
1039	Minimum Score Triangulation of Polygon		50.2%	Medium
1040	Moving Stones Until Consecutive II	Go	54.1%	Medium
1041	Robot Bounded In Circle		55.1%	Medium
1042	Flower Planting With No Adjacent		48.8%	Medium
1043	Partition Array for Maximum Sum		67.2%	Medium
1044	Longest Duplicate Substring		31.4%	Hard
1045	Customers Who Bought All Products		68.4%	Medium
1046	Last Stone Weight		62.4%	Easy
1047	Remove All Adjacent Duplicates In String	Go	70.9%	Easy
1048	Longest String Chain		55.5%	Medium
1049	Last Stone Weight II	Go	45.5%	Medium
1050	Actors and Directors Who Cooperated At Least Three Times		72.4%	Easy
1051	Height Checker	Go	72.1%	Easy
1052	Grumpy Bookstore Owner	Go	55.8%	Medium
1053	Previous Permutation With One Swap		51.1%	Medium
1054	Distant Barcodes	Go	44.2%	Medium
1055	Shortest Way to Form String		57.2%	Medium
1056	Confusing Number		47.0%	Easy
1057	Campus Bikes		57.8%	Medium
1058	Minimize Rounding Error to Meet Target		43.4%	Medium
1059	All Paths from Source Lead to Destination		42.9%	Medium
1060	Missing Element in Sorted Array		54.8%	Medium
1061	Lexicographically Smallest Equivalent String		66.8%	Medium
1062	Longest Repeating Substring		58.3%	Medium
1063	Number of Valid Subarrays		72.1%	Hard
1064	Fixed Point		64.9%	Easy
1065	Index Pairs of a String		61.0%	Easy
1066	Campus Bikes II		54.1%	Medium
1067	Digit Count in Range		41.7%	Hard
1068	Product Sales Analysis I		82.1%	Easy
1069	Product Sales Analysis II		83.2%	Easy
1070	Product Sales Analysis III		49.9%	Medium
1071	Greatest Common Divisor of Strings		51.2%	Easy
1072	Flip Columns For Maximum Number of Equal Rows		61.5%	Medium
1073	Adding Two Negabinary Numbers	Go	34.8%	Medium
1074	Number of Submatrices That Sum to Target	Go	61.9%	Hard
1075	Project Employees I		66.1%	Easy
1076	Project Employees II		52.9%	Easy
1077	Project Employees III		77.7%	Medium
1078	Occurrences After Bigram	Go	64.9%	Easy
1079	Letter Tile Possibilities	Go	75.9%	Medium
1080	Insufficient Nodes in Root to Leaf Paths		50.0%	Medium
1081	Smallest Subsequence of Distinct Characters		53.5%	Medium
1082	Sales Analysis I		73.8%	Easy
1083	Sales Analysis II		50.8%	Easy
1084	Sales Analysis III		54.7%	Easy
1085	Sum of Digits in the Minimum Number		75.1%	Easy
1086	High Five		77.6%	Easy
1087	Brace Expansion		63.1%	Medium
1088	Confusing Number II		45.5%	Hard
1089	Duplicate Zeros	Go	51.7%	Easy
1090	Largest Values From Labels		60.0%	Medium
1091	Shortest Path in Binary Matrix	Go	40.0%	Medium
1092	Shortest Common Supersequence		53.1%	Hard
1093	Statistics from a Large Sample	Go	49.2%	Medium
1094	Car Pooling		59.7%	Medium
1095	Find in Mountain Array		36.1%	Hard
1096	Brace Expansion II		62.6%	Hard
1097	Game Play Analysis V		56.5%	Hard
1098	Unpopular Books		45.5%	Medium
1099	Two Sum Less Than K		60.8%	Easy
1100	Find K-Length Substrings With No Repeated Characters		73.1%	Medium
1101	The Earliest Moment When Everyone Become Friends		67.8%	Medium
1102	Path With Maximum Minimum Value		50.6%	Medium
1103	Distribute Candies to People		63.5%	Easy
1104	Path In Zigzag Labelled Binary Tree		73.1%	Medium
1105	Filling Bookcase Shelves	Go	57.6%	Medium
1106	Parsing A Boolean Expression		59.3%	Hard
1107	New Users Daily Count		46.1%	Medium
1108	Defanging an IP Address	Go	88.4%	Easy
1109	Corporate Flight Bookings		54.3%	Medium
1110	Delete Nodes And Return Forest	Go	67.8%	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	Go	72.7%	Medium
1112	Highest Grade For Each Student		72.2%	Medium
1113	Reported Posts		65.9%	Easy
1114	Print in Order		67.2%	Easy
1115	Print FooBar Alternately		59.0%	Medium
1116	Print Zero Even Odd		57.8%	Medium
1117	Building H2O		53.1%	Medium
1118	Number of Days in a Month		57.3%	Easy
1119	Remove Vowels from a String		90.5%	Easy
1120	Maximum Average Subtree		63.6%	Medium
1121	Divide Array Into Increasing Sequences		58.2%	Hard
1122	Relative Sort Array	Go	68.1%	Easy
1123	Lowest Common Ancestor of Deepest Leaves	Go	67.9%	Medium
1124	Longest Well-Performing Interval		33.3%	Medium
1125	Smallest Sufficient Team		47.1%	Hard
1126	Active Businesses		68.5%	Medium
1127	User Purchase Platform		50.4%	Hard
1128	Number of Equivalent Domino Pairs	Go	46.4%	Easy
1129	Shortest Path with Alternating Colors		40.3%	Medium
1130	Minimum Cost Tree From Leaf Values		67.3%	Medium
1131	Maximum of Absolute Value Expression		51.9%	Medium
1132	Reported Posts II		34.6%	Medium
1133	Largest Unique Number		67.2%	Easy
1134	Armstrong Number		78.2%	Easy
1135	Connecting Cities With Minimum Cost		59.4%	Medium
1136	Parallel Courses		60.8%	Medium
1137	N-th Tribonacci Number	Go	55.9%	Easy
1138	Alphabet Board Path		51.2%	Medium
1139	Largest 1-Bordered Square		48.6%	Medium
1140	Stone Game II		64.7%	Medium
1141	User Activity for the Past 30 Days I		54.4%	Easy
1142	User Activity for the Past 30 Days II		35.4%	Easy
1143	Longest Common Subsequence		58.7%	Medium
1144	Decrease Elements To Make Array Zigzag		46.2%	Medium
1145	Binary Tree Coloring Game	Go	51.3%	Medium
1146	Snapshot Array		36.8%	Medium
1147	Longest Chunked Palindrome Decomposition		59.5%	Hard
1148	Article Views I		77.1%	Easy
1149	Article Views II		48.2%	Medium
1150	Check If a Number Is Majority Element in a Sorted Array		57.4%	Easy
1151	Minimum Swaps to Group All 1's Together		58.7%	Medium
1152	Analyze User Website Visit Pattern		43.2%	Medium
1153	String Transforms Into Another String		35.8%	Hard
1154	Day of the Year	Go	49.2%	Easy
1155	Number of Dice Rolls With Target Sum		47.6%	Medium
1156	Swap For Longest Repeated Character Substring		47.1%	Medium
1157	Online Majority Element In Subarray	Go	39.8%	Hard
1158	Market Analysis I		64.0%	Medium
1159	Market Analysis II		55.9%	Hard
1160	Find Words That Can Be Formed by Characters	Go	67.9%	Easy
1161	Maximum Level Sum of a Binary Tree		69.3%	Medium
1162	As Far from Land as Possible		45.5%	Medium
1163	Last Substring in Lexicographical Order		36.3%	Hard
1164	Product Price at a Given Date		68.6%	Medium
1165	Single-Row Keyboard		85.5%	Easy
1166	Design File System		58.5%	Medium
1167	Minimum Cost to Connect Sticks		64.5%	Medium
1168	Optimize Water Distribution in a Village		61.1%	Hard
1169	Invalid Transactions		30.9%	Medium
1170	Compare Strings by Frequency of the Smallest Character	Go	59.9%	Medium
1171	Remove Zero Sum Consecutive Nodes from Linked List	Go	41.5%	Medium
1172	Dinner Plate Stacks		37.7%	Hard
1173	Immediate Food Delivery I		82.5%	Easy
1174	Immediate Food Delivery II		61.9%	Medium
1175	Prime Arrangements	Go	52.0%	Easy
1176	Diet Plan Performance		53.8%	Easy
1177	Can Make Palindrome from Substring		36.0%	Medium
1178	Number of Valid Words for Each Puzzle	Go	39.4%	Hard
1179	Reformat Department Table		82.0%	Easy
1180	Count Substrings with Only One Distinct Letter		77.6%	Easy
1181	Before and After Puzzle		44.5%	Medium
1182	Shortest Distance to Target Color		53.4%	Medium
1183	Maximum Number of Ones		57.6%	Hard
1184	Distance Between Bus Stops	Go	54.0%	Easy
1185	Day of the Week	Go	61.3%	Easy
1186	Maximum Subarray Sum with One Deletion		38.8%	Medium
1187	Make Array Strictly Increasing		42.1%	Hard
1188	Design Bounded Blocking Queue		72.6%	Medium
1189	Maximum Number of Balloons	Go	61.9%	Easy
1190	Reverse Substrings Between Each Pair of Parentheses		64.1%	Medium
1191	K-Concatenation Maximum Sum		25.2%	Medium
1192	Critical Connections in a Network		50.2%	Hard
1193	Monthly Transactions I		69.0%	Medium
1194	Tournament Winners		52.3%	Hard
1195	Fizz Buzz Multithreaded		70.7%	Medium
1196	How Many Apples Can You Put into the Basket		68.1%	Easy
1197	Minimum Knight Moves		37.3%	Medium
1198	Find Smallest Common Element in All Rows		75.3%	Medium
1199	Minimum Time to Build Blocks		38.6%	Hard
1200	Minimum Absolute Difference	Go	67.0%	Easy
1201	Ugly Number III	Go	26.4%	Medium
1202	Smallest String With Swaps	Go	48.8%	Medium
1203	Sort Items by Groups Respecting Dependencies	Go	48.3%	Hard
1204	Last Person to Fit in the Elevator		71.9%	Medium
1205	Monthly Transactions II		45.7%	Medium
1206	Design Skiplist		58.8%	Hard
1207	Unique Number of Occurrences	Go	71.8%	Easy
1208	Get Equal Substrings Within Budget	Go	44.0%	Medium
1209	Remove All Adjacent Duplicates in String II		57.6%	Medium
1210	Minimum Moves to Reach Target with Rotations		46.4%	Hard
1211	Queries Quality and Percentage		70.0%	Easy
1212	Team Scores in Football Tournament		56.9%	Medium
1213	Intersection of Three Sorted Arrays		79.4%	Easy
1214	Two Sum BSTs		67.5%	Medium
1215	Stepping Numbers		43.6%	Medium
1216	Valid Palindrome III		49.9%	Hard
1217	Minimum Cost to Move Chips to The Same Position	Go	71.1%	Easy
1218	Longest Arithmetic Subsequence of Given Difference		46.7%	Medium
1219	Path with Maximum Gold		65.8%	Medium
1220	Count Vowels Permutation		54.0%	Hard
1221	Split a String in Balanced Strings	Go	84.3%	Easy
1222	Queens That Can Attack the King		69.5%	Medium
1223	Dice Roll Simulation		46.6%	Hard
1224	Maximum Equal Frequency		35.1%	Hard
1225	Report Contiguous Dates		62.9%	Hard
1226	The Dining Philosophers		59.6%	Medium
1227	Airplane Seat Assignment Probability		62.2%	Medium
1228	Missing Number In Arithmetic Progression		51.2%	Easy
1229	Meeting Scheduler		54.4%	Medium
1230	Toss Strange Coins		50.3%	Medium
1231	Divide Chocolate		53.6%	Hard
1232	Check If It Is a Straight Line	Go	43.4%	Easy
1233	Remove Sub-Folders from the Filesystem		62.2%	Medium
1234	Replace the Substring for Balanced String	Go	34.5%	Medium
1235	Maximum Profit in Job Scheduling	Go	47.4%	Hard
1236	Web Crawler		64.7%	Medium
1237	Find Positive Integer Solution for a Given Equation		69.4%	Medium
1238	Circular Permutation in Binary Representation		66.3%	Medium
1239	Maximum Length of a Concatenated String with Unique Characters		49.7%	Medium
1240	Tiling a Rectangle with the Fewest Squares		52.7%	Hard
1241	Number of Comments per Post		67.8%	Easy
1242	Web Crawler Multithreaded		47.5%	Medium
1243	Array Transformation		50.0%	Easy
1244	Design A Leaderboard		66.2%	Medium
1245	Tree Diameter		61.1%	Medium
1246	Palindrome Removal		46.0%	Hard
1247	Minimum Swaps to Make Strings Equal		62.8%	Medium
1248	Count Number of Nice Subarrays		56.1%	Medium
1249	Minimum Remove to Make Valid Parentheses	Go	64.2%	Medium
1250	Check If It Is a Good Array		56.2%	Hard
1251	Average Selling Price		82.6%	Easy
1252	Cells with Odd Values in a Matrix	Go	78.8%	Easy
1253	Reconstruct a 2-Row Binary Matrix		41.7%	Medium
1254	Number of Closed Islands	Go	61.7%	Medium
1255	Maximum Score Words Formed by Letters		70.0%	Hard
1256	Encode Number		68.0%	Medium
1257	Smallest Common Region		61.1%	Medium
1258	Synonymous Sentences		63.0%	Medium
1259	Handshakes That Don't Cross		54.3%	Hard
1260	Shift 2D Grid	Go	61.9%	Easy
1261	Find Elements in a Contaminated Binary Tree		74.5%	Medium
1262	Greatest Sum Divisible by Three		49.7%	Medium
1263	Minimum Moves to Move a Box to Their Target Location		43.4%	Hard
1264	Page Recommendations		69.2%	Medium
1265	Print Immutable Linked List in Reverse		94.3%	Medium
1266	Minimum Time Visiting All Points	Go	79.3%	Easy
1267	Count Servers that Communicate		57.7%	Medium
1268	Search Suggestions System		64.7%	Medium
1269	Number of Ways to Stay in the Same Place After Some Steps		43.2%	Hard
1270	All People Report to the Given Manager		88.2%	Medium
1271	Hexspeak		55.4%	Easy
1272	Remove Interval		58.2%	Medium
1273	Delete Tree Nodes		62.1%	Medium
1274	Number of Ships in a Rectangle		65.9%	Hard
1275	Find Winner on a Tic Tac Toe Game	Go	52.9%	Easy
1276	Number of Burgers with No Waste of Ingredients		50.1%	Medium
1277	Count Square Submatrices with All Ones		72.8%	Medium
1278	Palindrome Partitioning III		61.0%	Hard
1279	Traffic Light Controlled Intersection		76.1%	Easy
1280	Students and Examinations		75.0%	Easy
1281	Subtract the Product and Sum of Digits of an Integer	Go	85.6%	Easy
1282	Group the People Given the Group Size They Belong To		84.4%	Medium
1283	Find the Smallest Divisor Given a Threshold	Go	49.7%	Medium
1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix		70.1%	Hard
1285	Find the Start and End Number of Continuous Ranges		87.4%	Medium
1286	Iterator for Combination		70.9%	Medium
1287	Element Appearing More Than 25% In Sorted Array	Go	60.1%	Easy
1288	Remove Covered Intervals		57.3%	Medium
1289	Minimum Falling Path Sum II		62.5%	Hard
1290	Convert Binary Number in a Linked List to Integer	Go	81.8%	Easy
1291	Sequential Digits		57.4%	Medium
1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold		50.8%	Medium
1293	Shortest Path in a Grid with Obstacles Elimination		43.1%	Hard
1294	Weather Type in Each Country		66.5%	Easy
1295	Find Numbers with Even Number of Digits	Go	78.9%	Easy
1296	Divide Array in Sets of K Consecutive Numbers		55.5%	Medium
1297	Maximum Number of Occurrences of a Substring		50.3%	Medium
1298	Maximum Candies You Can Get from Boxes		59.7%	Hard
1299	Replace Elements with Greatest Element on Right Side	Go	74.5%	Easy
1300	Sum of Mutated Array Closest to Target	Go	43.0%	Medium
1301	Number of Paths with Max Score		38.3%	Hard
1302	Deepest Leaves Sum	Go	84.2%	Medium
1303	Find the Team Size		89.6%	Easy
1304	Find N Unique Integers Sum up to Zero	Go	76.8%	Easy
1305	All Elements in Two Binary Search Trees	Go	77.8%	Medium
1306	Jump Game III	Go	62.3%	Medium
1307	Verbal Arithmetic Puzzle		36.8%	Hard
1308	Running Total for Different Genders		87.7%	Medium
1309	Decrypt String from Alphabet to Integer Mapping		77.6%	Easy
1310	XOR Queries of a Subarray		69.4%	Medium
1311	Get Watched Videos by Your Friends		44.2%	Medium
1312	Minimum Insertion Steps to Make a String Palindrome		59.8%	Hard
1313	Decompress Run-Length Encoded List	Go	85.4%	Easy
1314	Matrix Block Sum		73.6%	Medium
1315	Sum of Nodes with Even-Valued Grandparent		84.3%	Medium
1316	Distinct Echo Substrings		49.7%	Hard
1317	Convert Integer to the Sum of Two No-Zero Integers	Go	56.8%	Easy
1318	Minimum Flips to Make a OR b Equal to c		63.9%	Medium
1319	Number of Operations to Make Network Connected	Go	55.5%	Medium
1320	Minimum Distance to Type a Word Using Two Fingers		61.8%	Hard
1321	Restaurant Growth		71.4%	Medium
1322	Ads Performance		58.1%	Easy
1323	Maximum 69 Number		77.9%	Easy
1324	Print Words Vertically		59.0%	Medium
1325	Delete Leaves With a Given Value		73.8%	Medium
1326	Minimum Number of Taps to Open to Water a Garden		47.6%	Hard
1327	List the Products Ordered in a Period		77.6%	Easy
1328	Break a Palindrome		47.0%	Medium
1329	Sort the Matrix Diagonally	Go	81.7%	Medium
1330	Reverse Subarray To Maximize Array Value		36.7%	Hard
1331	Rank Transform of an Array		57.4%	Easy
1332	Remove Palindromic Subsequences	Go	68.1%	Easy
1333	Filter Restaurants by Vegan-Friendly, Price and Distance		57.2%	Medium
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance		47.1%	Medium
1335	Minimum Difficulty of a Job Schedule		56.8%	Hard
1336	Number of Transactions per Visit		48.4%	Hard
1337	The K Weakest Rows in a Matrix	Go	72.0%	Easy
1338	Reduce Array Size to The Half		67.7%	Medium
1339	Maximum Product of Splitted Binary Tree		38.3%	Medium
1340	Jump Game V		59.3%	Hard
1341	Movie Rating		58.8%	Medium
1342	Number of Steps to Reduce a Number to Zero		85.8%	Easy
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold		64.8%	Medium
1344	Angle Between Hands of a Clock		61.3%	Medium
1345	Jump Game IV		42.0%	Hard
1346	Check If N and Its Double Exist		36.1%	Easy
1347	Minimum Number of Steps to Make Two Strings Anagram		75.1%	Medium
1348	Tweet Counts Per Frequency		36.3%	Medium
1349	Maximum Students Taking Exam		44.2%	Hard
1350	Students With Invalid Departments		90.3%	Easy
1351	Count Negative Numbers in a Sorted Matrix		75.9%	Easy
1352	Product of the Last K Numbers		44.7%	Medium
1353	Maximum Number of Events That Can Be Attended		30.5%	Medium
1354	Construct Target Array With Multiple Sums		31.3%	Hard
1355	Activity Participants		74.3%	Medium
1356	Sort Integers by The Number of 1 Bits		69.6%	Easy
1357	Apply Discount Every n Orders		66.9%	Medium
1358	Number of Substrings Containing All Three Characters		60.6%	Medium
1359	Count All Valid Pickup and Delivery Options		56.3%	Hard
1360	Number of Days Between Two Dates		46.7%	Easy
1361	Validate Binary Tree Nodes		43.6%	Medium
1362	Closest Divisors		57.7%	Medium
1363	Largest Multiple of Three		34.1%	Hard
1364	Number of Trusted Contacts of a Customer		78.9%	Medium
1365	How Many Numbers Are Smaller Than the Current Number		86.0%	Easy
1366	Rank Teams by Votes		55.4%	Medium
1367	Linked List in Binary Tree		41.1%	Medium
1368	Minimum Cost to Make at Least One Valid Path in a Grid		57.4%	Hard
1369	Get the Second Most Recent Activity		68.8%	Hard
1370	Increasing Decreasing String		77.2%	Easy
1371	Find the Longest Substring Containing Vowels in Even Counts		60.9%	Medium
1372	Longest ZigZag Path in a Binary Tree		54.9%	Medium
1373	Maximum Sum BST in Binary Tree		37.3%	Hard
1374	Generate a String With Characters That Have Odd Counts		76.7%	Easy
1375	Bulb Switcher III		64.2%	Medium
1376	Time Needed to Inform All Employees		56.5%	Medium
1377	Frog Position After T Seconds		35.2%	Hard
1378	Replace Employee ID With The Unique Identifier		90.1%	Easy
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree		84.6%	Medium
1380	Lucky Numbers in a Matrix	Go	70.6%	Easy
1381	Design a Stack With Increment Operation		76.2%	Medium
1382	Balance a Binary Search Tree		76.1%	Medium
1383	Maximum Performance of a Team		35.8%	Hard
1384	Total Sales Amount by Year		64.5%	Hard
1385	Find the Distance Value Between Two Arrays	Go	66.4%	Easy
1386	Cinema Seat Allocation		35.8%	Medium
1387	Sort Integers by The Power Value		70.5%	Medium
1388	Pizza With 3n Slices		45.8%	Hard
1389	Create Target Array in the Given Order	Go	84.8%	Easy
1390	Four Divisors		39.3%	Medium
1391	Check if There is a Valid Path in a Grid		45.0%	Medium
1392	Longest Happy Prefix		41.9%	Hard
1393	Capital Gain/Loss		90.9%	Medium
1394	Find Lucky Integer in an Array		63.2%	Easy
1395	Count Number of Teams		76.5%	Medium
1396	Design Underground System		69.7%	Medium
1397	Find All Good Strings		38.6%	Hard
1398	Customers Who Bought Products A and B but Not C		82.0%	Medium
1399	Count Largest Group		65.3%	Easy
1400	Construct K Palindrome Strings		63.1%	Medium
1401	Circle and Rectangle Overlapping		42.5%	Medium
1402	Reducing Dishes		72.1%	Hard
1403	Minimum Subsequence in Non-Increasing Order		71.0%	Easy
1404	Number of Steps to Reduce a Number in Binary Representation to One		49.8%	Medium
1405	Longest Happy String		52.5%	Medium
1406	Stone Game III		57.5%	Hard
1407	Top Travellers		83.8%	Easy
1408	String Matching in an Array		63.3%	Easy
1409	Queries on a Permutation With Key		81.6%	Medium
1410	HTML Entity Parser		54.2%	Medium
1411	Number of Ways to Paint N × 3 Grid		60.5%	Hard
1412	Find the Quiet Students in All Exams		64.0%	Hard
1413	Minimum Value to Get Positive Step by Step Sum		65.5%	Easy
1414	Find the Minimum Number of Fibonacci Numbers Whose Sum Is K		63.2%	Medium
1415	The k-th Lexicographical String of All Happy Strings of Length n		69.9%	Medium
1416	Restore The Array		36.5%	Hard
1417	Reformat The String		55.3%	Easy
1418	Display Table of Food Orders in a Restaurant		69.0%	Medium
1419	Minimum Number of Frogs Croaking		47.5%	Medium
1420	Build Array Where You Can Find The Maximum Exactly K Comparisons		64.1%	Hard
1421	NPV Queries		82.1%	Medium
1422	Maximum Score After Splitting a String		56.4%	Easy
1423	Maximum Points You Can Obtain from Cards	Go	46.7%	Medium
1424	Diagonal Traverse II		46.1%	Medium
1425	Constrained Subsequence Sum		45.0%	Hard
1426	Counting Elements		59.1%	Easy
1427	Perform String Shifts		53.5%	Easy
1428	Leftmost Column with at Least a One		49.2%	Medium
1429	First Unique Number		49.7%	Medium
1430	Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree		45.2%	Medium
1431	Kids With the Greatest Number of Candies		88.2%	Easy
1432	Max Difference You Can Get From Changing an Integer		42.9%	Medium
1433	Check If a String Can Break Another String		67.3%	Medium
1434	Number of Ways to Wear Different Hats to Each Other		39.4%	Hard
1435	Create a Session Bar Chart		77.8%	Easy
1436	Destination City		77.3%	Easy
1437	Check If All 1's Are at Least Length K Places Away	Go	62.3%	Easy
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Go	44.4%	Medium
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows	Go	60.1%	Hard
1440	Evaluate Boolean Expression		74.8%	Medium
1441	Build an Array With Stack Operations		70.4%	Easy
1442	Count Triplets That Can Form Two Arrays of Equal XOR		71.4%	Medium
1443	Minimum Time to Collect All Apples in a Tree		54.6%	Medium
1444	Number of Ways of Cutting a Pizza		53.9%	Hard
1445	Apples & Oranges		90.7%	Medium
1446	Consecutive Characters		61.1%	Easy
1447	Simplified Fractions		62.1%	Medium
1448	Count Good Nodes in Binary Tree		70.9%	Medium
1449	Form Largest Integer With Digits That Add up to Target		44.2%	Hard
1450	Number of Students Doing Homework at a Given Time		77.1%	Easy
1451	Rearrange Words in a Sentence		59.7%	Medium
1452	People Whose List of Favorite Companies Is Not a Subset of Another List		55.0%	Medium
1453	Maximum Number of Darts Inside of a Circular Dartboard		35.4%	Hard
1454	Active Users		38.8%	Medium
1455	Check If a Word Occurs As a Prefix of Any Word in a Sentence	Go	65.0%	Easy
1456	Maximum Number of Vowels in a Substring of Given Length		54.7%	Medium
1457	Pseudo-Palindromic Paths in a Binary Tree		70.5%	Medium
1458	Max Dot Product of Two Subsequences		43.2%	Hard
1459	Rectangles Area		64.9%	Medium
1460	Make Two Arrays Equal by Reversing Sub-arrays		72.1%	Easy
1461	Check If a String Contains All Binary Codes of Size K		54.5%	Medium
1462	Course Schedule IV		44.7%	Medium
1463	Cherry Pickup II	Go	69.0%	Hard
1464	Maximum Product of Two Elements in an Array	Go	77.2%	Easy
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts		33.3%	Medium
1466	Reorder Routes to Make All Paths Lead to the City Zero		61.8%	Medium
1467	Probability of a Two Boxes Having The Same Number of Distinct Balls		60.9%	Hard
1468	Calculate Salaries		82.0%	Medium
1469	Find All The Lonely Nodes		80.4%	Easy
1470	Shuffle the Array	Go	88.2%	Easy
1471	The k Strongest Values in an Array		58.4%	Medium
1472	Design Browser History		71.5%	Medium
1473	Paint House III		48.5%	Hard
1474	Delete N Nodes After M Nodes of a Linked List		74.2%	Easy
1475	Final Prices With a Special Discount in a Shop		75.1%	Easy
1476	Subrectangle Queries		88.2%	Medium
1477	Find Two Non-overlapping Sub-arrays Each With Target Sum		34.6%	Medium
1478	Allocate Mailboxes		54.0%	Hard
1479	Sales by Day of the Week		83.4%	Hard
1480	Running Sum of 1d Array	Go	88.9%	Easy
1481	Least Number of Unique Integers after K Removals		56.0%	Medium
1482	Minimum Number of Days to Make m Bouquets		50.4%	Medium
1483	Kth Ancestor of a Tree Node		30.7%	Hard
1484	Group Sold Products By The Date		85.4%	Easy
1485	Clone Binary Tree With Random Pointer		79.3%	Medium
1486	XOR Operation in an Array		84.1%	Easy
1487	Making File Names Unique		30.8%	Medium
1488	Avoid Flood in The City		24.5%	Medium
1489	Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree		51.5%	Hard
1490	Clone N-ary Tree		83.5%	Medium
1491	Average Salary Excluding the Minimum and Maximum Salary		68.5%	Easy
1492	The kth Factor of n		63.3%	Medium
1493	Longest Subarray of 1's After Deleting One Element		57.7%	Medium
1494	Parallel Courses II		31.1%	Hard
1495	Friendly Movies Streamed Last Month		51.3%	Easy
1496	Path Crossing		55.2%	Easy
1497	Check If Array Pairs Are Divisible by k		40.3%	Medium
1498	Number of Subsequences That Satisfy the Given Sum Condition		38.5%	Medium
1499	Max Value of Equation		44.9%	Hard
1500	Design a File Sharing System		46.1%	Medium
1501	Countries You Can Safely Invest In		60.5%	Medium
1502	Can Make Arithmetic Progression From Sequence		71.1%	Easy
1503	Last Moment Before All Ants Fall Out of a Plank		53.2%	Medium
1504	Count Submatrices With All Ones		60.9%	Medium
1505	Minimum Possible Integer After at Most K Adjacent Swaps On Digits		36.6%	Hard
1506	Find Root of N-Ary Tree		80.3%	Medium
1507	Reformat Date		60.1%	Easy
1508	Range Sum of Sorted Subarray Sums		60.8%	Medium
1509	Minimum Difference Between Largest and Smallest Value in Three Moves		52.4%	Medium
1510	Stone Game IV		58.9%	Hard
1511	Customer Order Frequency		73.7%	Easy
1512	Number of Good Pairs	Go	87.7%	Easy
1513	Number of Substrings With Only 1s		41.9%	Medium
1514	Path with Maximum Probability		40.7%	Medium
1515	Best Position for a Service Centre		38.1%	Hard
1516	Move Sub-Tree of N-Ary Tree		63.9%	Hard
1517	Find Users With Valid E-Mails		71.1%	Easy
1518	Water Bottles		60.5%	Easy
1519	Number of Nodes in the Sub-Tree With the Same Label		37.1%	Medium
1520	Maximum Number of Non-Overlapping Substrings		36.3%	Hard
1521	Find a Value of a Mysterious Function Closest to Target		44.3%	Hard
1522	Diameter of N-Ary Tree		69.0%	Medium
1523	Count Odd Numbers in an Interval Range		54.5%	Easy
1524	Number of Sub-arrays With Odd Sum		40.0%	Medium
1525	Number of Good Ways to Split a String		66.4%	Medium
1526	Minimum Number of Increments on Subarrays to Form a Target Array		60.0%	Hard
1527	Patients With a Condition		65.4%	Easy
1528	Shuffle String		85.6%	Easy
1529	Bulb Switcher IV		70.8%	Medium
1530	Number of Good Leaf Nodes Pairs		56.2%	Medium
1531	String Compression II		33.9%	Hard
1532	The Most Recent Three Orders		72.8%	Medium
1533	Find the Index of the Large Integer		54.7%	Medium
1534	Count Good Triplets		80.3%	Easy
1535	Find the Winner of an Array Game		47.6%	Medium
1536	Minimum Swaps to Arrange a Binary Grid		43.5%	Medium
1537	Get the Maximum Score		36.4%	Hard
1538	Guess the Majority in a Hidden Array		61.0%	Medium
1539	Kth Missing Positive Number	Go	55.0%	Easy
1540	Can Convert String in K Moves		31.0%	Medium
1541	Minimum Insertions to Balance a Parentheses String		42.8%	Medium
1542	Find Longest Awesome Substring		36.7%	Hard
1543	Fix Product Name Format		67.4%	Easy
1544	Make The String Great		55.5%	Easy
1545	Find Kth Bit in Nth Binary String		57.5%	Medium
1546	Maximum Number of Non-Overlapping Subarrays With Sum Equals Target		43.8%	Medium
1547	Minimum Cost to Cut a Stick		52.8%	Hard
1548	The Most Similar Path in a Graph		54.4%	Hard
1549	The Most Recent Orders for Each Product		66.9%	Medium
1550	Three Consecutive Odds		64.6%	Easy
1551	Minimum Operations to Make Array Equal		77.9%	Medium
1552	Magnetic Force Between Two Balls		48.9%	Medium
1553	Minimum Number of Days to Eat N Oranges		29.7%	Hard
1554	Strings Differ by One Character		63.5%	Medium
1555	Bank Account Summary		52.7%	Medium
1556	Thousand Separator		57.5%	Easy
1557	Minimum Number of Vertices to Reach All Nodes		75.5%	Medium
1558	Minimum Numbers of Function Calls to Make Target Array		63.4%	Medium
1559	Detect Cycles in 2D Grid		44.5%	Hard
1560	Most Visited Sector in a Circular Track		56.9%	Easy
1561	Maximum Number of Coins You Can Get		77.5%	Medium
1562	Find Latest Group of Size M		39.5%	Medium
1563	Stone Game V		39.9%	Hard
1564	Put Boxes Into the Warehouse I		66.1%	Medium
1565	Unique Orders and Customers Per Month		82.9%	Easy
1566	Detect Pattern of Length M Repeated K or More Times		42.5%	Easy
1567	Maximum Length of Subarray With Positive Product		36.7%	Medium
1568	Minimum Number of Days to Disconnect Island		50.2%	Hard
1569	Number of Ways to Reorder Array to Get Same BST		50.0%	Hard
1570	Dot Product of Two Sparse Vectors		91.2%	Medium
1571	Warehouse Manager		89.7%	Easy
1572	Matrix Diagonal Sum		77.8%	Easy
1573	Number of Ways to Split a String	Go	31.3%	Medium
1574	Shortest Subarray to be Removed to Make Array Sorted		33.5%	Medium
1575	Count All Possible Routes		57.3%	Hard
1576	Replace All ?'s to Avoid Consecutive Repeating Characters		48.7%	Easy
1577	Number of Ways Where Square of Number Is Equal to Product of Two Numbers		37.5%	Medium
1578	Minimum Deletion Cost to Avoid Repeating Letters		60.5%	Medium
1579	Remove Max Number of Edges to Keep Graph Fully Traversable	Go	46.2%	Hard
1580	Put Boxes Into the Warehouse II		62.2%	Medium
1581	Customer Who Visited but Did Not Make Any Transactions		89.6%	Easy
1582	Special Positions in a Binary Matrix		64.4%	Easy
1583	Count Unhappy Friends		54.5%	Medium
1584	Min Cost to Connect All Points		52.3%	Medium
1585	Check If String Is Transformable With Substring Sort Operations		48.3%	Hard
1586	Binary Search Tree Iterator II		66.6%	Medium
1587	Bank Account Summary II		89.8%	Easy
1588	Sum of All Odd Length Subarrays		81.6%	Easy
1589	Maximum Sum Obtained of Any Permutation		34.8%	Medium
1590	Make Sum Divisible by P		27.0%	Medium
1591	Strange Printer II		55.0%	Hard
1592	Rearrange Spaces Between Words		43.7%	Easy
1593	Split a String Into the Max Number of Unique Substrings		49.4%	Medium
1594	Maximum Non Negative Product in a Matrix		31.8%	Medium
1595	Minimum Cost to Connect Two Groups of Points		43.3%	Hard
1596	The Most Frequently Ordered Products for Each Customer		84.9%	Medium
1597	Build Binary Expression Tree From Infix Expression		60.3%	Hard
1598	Crawler Log Folder		63.9%	Easy
1599	Maximum Profit of Operating a Centennial Wheel		43.7%	Medium
1600	Throne Inheritance		60.5%	Medium
1601	Maximum Number of Achievable Transfer Requests		47.8%	Hard
1602	Find Nearest Right Node in Binary Tree		73.8%	Medium
1603	Design Parking System	Go	86.3%	Easy
1604	Alert Using Same Key-Card Three or More Times in a One Hour Period		42.7%	Medium
1605	Find Valid Matrix Given Row and Column Sums		77.3%	Medium
1606	Find Servers That Handled Most Number of Requests		37.2%	Hard
1607	Sellers With No Sales		55.4%	Easy
1608	Special Array With X Elements Greater Than or Equal X	Go	61.3%	Easy
1609	Even Odd Tree		52.6%	Medium
1610	Maximum Number of Visible Points		30.0%	Hard
1611	Minimum One Bit Operations to Make Integers Zero		57.2%	Hard
1612	Check If Two Expression Trees are Equivalent		69.9%	Medium
1613	Find the Missing IDs		74.1%	Medium
1614	Maximum Nesting Depth of the Parentheses	Go	82.8%	Easy
1615	Maximal Network Rank		52.4%	Medium
1616	Split Two Strings to Make Palindrome		36.2%	Medium
1617	Count Subtrees With Max Distance Between Cities		63.2%	Hard
1618	Maximum Font to Fit a Sentence in a Screen		56.5%	Medium
1619	Mean of Array After Removing Some Elements	Go	64.9%	Easy
1620	Coordinate With Maximum Network Quality		37.1%	Medium
1621	Number of Sets of K Non-Overlapping Line Segments		41.2%	Medium
1622	Fancy Sequence		15.0%	Hard
1623	All Valid Triplets That Can Represent a Country		88.6%	Easy
1624	Largest Substring Between Two Equal Characters	Go	58.7%	Easy
1625	Lexicographically Smallest String After Applying Operations		64.3%	Medium
1626	Best Team With No Conflicts		38.2%	Medium
1627	Graph Connectivity With Threshold		39.3%	Hard
1628	Design an Expression Tree With Evaluate Function		80.6%	Medium
1629	Slowest Key	Go	59.1%	Easy
1630	Arithmetic Subarrays		77.5%	Medium
1631	Path With Minimum Effort	Go	50.1%	Medium
1632	Rank Transform of a Matrix		30.8%	Hard
1633	Percentage of Users Attended a Contest		71.0%	Easy
1634	Add Two Polynomials Represented as Linked Lists		55.2%	Medium
1635	Hopper Company Queries I		55.8%	Hard
1636	Sort Array by Increasing Frequency	Go	66.9%	Easy
1637	Widest Vertical Area Between Two Points Containing No Points		83.6%	Medium
1638	Count Substrings That Differ by One Character		69.6%	Medium
1639	Number of Ways to Form a Target String Given a Dictionary		39.8%	Hard
1640	Check Array Formation Through Concatenation	Go	59.9%	Easy
1641	Count Sorted Vowel Strings	Go	76.2%	Medium
1642	Furthest Building You Can Reach		50.3%	Medium
1643	Kth Smallest Instructions		44.0%	Hard
1644	Lowest Common Ancestor of a Binary Tree II		56.5%	Medium
1645	Hopper Company Queries II		37.9%	Hard
1646	Get Maximum in Generated Array	Go	53.3%	Easy
1647	Minimum Deletions to Make Character Frequencies Unique	Go	54.7%	Medium
1648	Sell Diminishing-Valued Colored Balls	Go	30.5%	Medium
1649	Create Sorted Array through Instructions	Go	36.4%	Hard
1650	Lowest Common Ancestor of a Binary Tree III		76.4%	Medium
1651	Hopper Company Queries III		65.9%	Hard
1652	Defuse the Bomb	Go	62.4%	Easy
1653	Minimum Deletions to Make String Balanced	Go	51.3%	Medium
1654	Minimum Jumps to Reach Home	Go	25.6%	Medium
1655	Distribute Repeating Integers	Go	39.9%	Hard
1656	Design an Ordered Stream	Go	82.0%	Easy
1657	Determine if Two Strings Are Close	Go	55.3%	Medium
1658	Minimum Operations to Reduce X to Zero	Go	33.4%	Medium
1659	Maximize Grid Happiness	Go	35.5%	Hard
1660	Correct a Binary Tree		77.3%	Medium
1661	Average Time of Process per Machine		79.4%	Easy
1662	Check If Two String Arrays are Equivalent	Go	82.8%	Easy
1663	Smallest String With A Given Numeric Value	Go	64.3%	Medium
1664	Ways to Make a Fair Array	Go	62.0%	Medium
1665	Minimum Initial Energy to Finish Tasks	Go	65.8%	Hard
1666	Change the Root of a Binary Tree		67.6%	Medium
1667	Fix Names in a Table		63.1%	Easy
1668	Maximum Repeating Substring	Go	38.8%	Easy
1669	Merge In Between Linked Lists	Go	76.1%	Medium
1670	Design Front Middle Back Queue	Go	54.2%	Medium
1671	Minimum Number of Removals to Make Mountain Array		45.7%	Hard
1672	Richest Customer Wealth	Go	88.2%	Easy
1673	Find the Most Competitive Subsequence	Go	45.4%	Medium
1674	Minimum Moves to Make Array Complementary	Go	35.0%	Medium
1675	Minimize Deviation in Array	Go	48.3%	Hard
1676	Lowest Common Ancestor of a Binary Tree IV		78.9%	Medium
1677	Product's Worth Over Invoices		73.5%	Easy
1678	Goal Parser Interpretation	Go	85.3%	Easy
1679	Max Number of K-Sum Pairs	Go	54.0%	Medium
1680	Concatenation of Consecutive Binary Numbers	Go	52.3%	Medium
1681	Minimum Incompatibility	Go	35.7%	Hard
1682	Longest Palindromic Subsequence II		51.4%	Medium
1683	Invalid Tweets		90.8%	Easy
1684	Count the Number of Consistent Strings	Go	82.2%	Easy
1685	Sum of Absolute Differences in a Sorted Array	Go	62.8%	Medium
1686	Stone Game VI		49.6%	Medium
1687	Delivering Boxes from Storage to Ports		35.0%	Hard
1688	Count of Matches in Tournament	Go	81.5%	Easy
1689	Partitioning Into Minimum Number Of Deci-Binary Numbers	Go	87.2%	Medium
1690	Stone Game VII	Go	48.4%	Medium
1691	Maximum Height by Stacking Cuboids	Go	50.0%	Hard
1692	Count Ways to Distribute Candies		62.4%	Hard
1693	Daily Leads and Partners		90.9%	Easy
1694	Reformat Phone Number	Go	65.7%	Easy
1695	Maximum Erasure Value	Go	49.5%	Medium
1696	Jump Game VI	Go	52.9%	Medium
1697	Checking Existence of Edge Length Limited Paths		54.5%	Hard
1698	Number of Distinct Substrings in a String		60.0%	Medium
1699	Number of Calls Between Two Persons		86.6%	Medium
1700	Number of Students Unable to Eat Lunch	Go	68.1%	Easy
1701	Average Waiting Time		61.5%	Medium
1702	Maximum Binary String After Change		59.9%	Medium
1703	Minimum Adjacent Swaps for K Consecutive Ones		39.8%	Hard
1704	Determine if String Halves Are Alike	Go	77.0%	Easy
1705	Maximum Number of Eaten Apples		42.0%	Medium
1706	Where Will the Ball Fall		60.0%	Medium
1707	Maximum XOR With an Element From Array		46.8%	Hard
1708	Largest Subarray Length K		63.0%	Easy
1709	Biggest Window Between Visits		82.5%	Medium
1710	Maximum Units on a Truck	Go	70.2%	Easy
1711	Count Good Meals		26.1%	Medium
1712	Ways to Split Array Into Three Subarrays		29.4%	Medium
1713	Minimum Operations to Make a Subsequence		45.5%	Hard
1714	Sum Of Special Evenly-Spaced Elements In Array		48.3%	Hard
1715	Count Apples and Oranges		79.7%	Medium
1716	Calculate Money in Leetcode Bank	Go	66.5%	Easy
1717	Maximum Score From Removing Substrings		40.4%	Medium
1718	Construct the Lexicographically Largest Valid Sequence		46.5%	Medium
1719	Number Of Ways To Reconstruct A Tree		39.6%	Hard
1720	Decode XORed Array	Go	85.3%	Easy
1721	Swapping Nodes in a Linked List		64.4%	Medium
1722	Minimize Hamming Distance After Swap Operations		54.4%	Medium
1723	Find Minimum Time to Finish All Jobs		43.8%	Hard
1724	Checking Existence of Edge Length Limited Paths II		56.5%	Hard
1725	Number Of Rectangles That Can Form The Largest Square	Go	77.8%	Easy
1726	Tuple with Same Product		56.2%	Medium
1727	Largest Submatrix With Rearrangements		58.4%	Medium
1728	Cat and Mouse II		41.0%	Hard
1729	Find Followers Count		71.8%	Easy
1730	Shortest Path to Get Food		56.9%	Medium
1731	The Number of Employees Which Report to Each Employee		49.5%	Easy
1732	Find the Highest Altitude	Go	80.6%	Easy
1733	Minimum Number of People to Teach		37.3%	Medium
1734	Decode XORed Permutation		52.5%	Medium
1735	Count Ways to Make Array With Product		48.2%	Hard
1736	Latest Time by Replacing Hidden Digits	Go	41.1%	Easy
1737	Change Minimum Characters to Satisfy One of Three Conditions		29.6%	Medium
1738	Find Kth Largest XOR Coordinate Value		62.1%	Medium
1739	Building Boxes		49.6%	Hard
1740	Find Distance in a Binary Tree		68.5%	Medium
1741	Find Total Time Spent by Each Employee		90.9%	Easy
1742	Maximum Number of Balls in a Box	Go	74.5%	Easy
1743	Restore the Array From Adjacent Pairs		63.0%	Medium
1744	Can You Eat Your Favorite Candy on Your Favorite Day?		30.4%	Medium
1745	Palindrome Partitioning IV		49.2%	Hard
1746	Maximum Subarray Sum After One Operation		62.4%	Medium
1747	Leetflex Banned Accounts		70.1%	Medium
1748	Sum of Unique Elements	Go	75.2%	Easy
1749	Maximum Absolute Sum of Any Subarray		51.7%	Medium
1750	Minimum Length of String After Deleting Similar Ends		42.5%	Medium
1751	Maximum Number of Events That Can Be Attended II		47.5%	Hard
1752	Check if Array Is Sorted and Rotated	Go	63.0%	Easy
1753	Maximum Score From Removing Stones		61.2%	Medium
1754	Largest Merge Of Two Strings		40.1%	Medium
1755	Closest Subsequence Sum		35.6%	Hard
1756	Design Most Recently Used Queue		77.7%	Medium
1757	Recyclable and Low Fat Products		96.1%	Easy
1758	Minimum Changes To Make Alternating Binary String	Go	58.7%	Easy
1759	Count Number of Homogenous Substrings		41.9%	Medium
1760	Minimum Limit of Balls in a Bag		52.4%	Medium
1761	Minimum Degree of a Connected Trio in a Graph		37.3%	Hard
1762	Buildings With an Ocean View		82.1%	Medium
1763	Longest Nice Substring		61.6%	Easy
1764	Form Array by Concatenating Subarrays of Another Array		55.4%	Medium
1765	Map of Highest Peak		54.6%	Medium
1766	Tree of Coprimes		36.7%	Hard
1767	Find the Subtasks That Did Not Execute		87.7%	Hard
1768	Merge Strings Alternately		77.2%	Easy
1769	Minimum Number of Operations to Move All Balls to Each Box		87.6%	Medium
1770	Maximum Score from Performing Multiplication Operations		29.0%	Medium
1771	Maximize Palindrome Length From Subsequences		34.0%	Hard
1772	Sort Features by Popularity		65.9%	Medium
1773	Count Items Matching a Rule		86.2%	Easy
1774	Closest Dessert Cost		59.6%	Medium
1775	Equal Sum Arrays With Minimum Number of Operations		50.6%	Medium
1776	Car Fleet II		44.1%	Hard
1777	Product's Price for Each Store		87.1%	Easy
1778	Shortest Path in a Hidden Grid		46.0%	Medium
1779	Find Nearest Point That Has the Same X or Y Coordinate		67.8%	Easy
1780	Check if Number is a Sum of Powers of Three		63.2%	Medium
1781	Sum of Beauty of All Substrings		56.6%	Medium
1782	Count Pairs Of Nodes		31.1%	Hard
1783	Grand Slam Titles		92.7%	Medium
1784	Check if Binary String Has at Most One Segment of Ones		41.9%	Easy
1785	Minimum Elements to Add to Form a Given Sum		38.7%	Medium
1786	Number of Restricted Paths From First to Last Node		35.8%	Medium
1787	Make the XOR of All Segments Equal to Zero		35.2%	Hard
1788	Maximize the Beauty of the Garden		71.2%	Hard
1789	Primary Department for Each Employee		78.6%	Easy
1790	Check if One String Swap Can Make Strings Equal		44.2%	Easy
1791	Find Center of Star Graph		86.4%	Medium
1792	Maximum Average Pass Ratio		38.6%	Medium
1793	Maximum Score of a Good Subarray		38.4%	Hard
------------	-------------------------------------------------------	-------	----------------	---------------	-------------

---

下面这些是免费的算法题，但是暂时还不能使用 Go 解答的：

暂无

---

三.分类

Array

Problems List in there

String

Problems List in there

Two Pointers

• 双指针滑动窗口的经典写法。右指针不断往右移，移动到不能往右移动为止(具体条件根据题目而定)。当右指针到最右边以后，开始挪动左指针，释放窗口左边界。第 3 题，第 76 题，第 209 题，第 424 题，第 438 题，第 567 题，第 713 题，第 763 题，第 845 题，第 881 题，第 904 题，第 978 题，第 992 题，第 1004 题，第 1040 题，第 1052 题。

	left, right := 0, -1

	for left < len(s) {
		if right+1 < len(s) && freq[s[right+1]-'a'] == 0 {
			freq[s[right+1]-'a']++
			right++
		} else {
			freq[s[left]-'a']--
			left++
		}
		result = max(result, right-left+1)
	}

• 快慢指针可以查找重复数字，时间复杂度 O(n)，第 287 题。
• 替换字母以后，相同字母能出现连续最长的长度。第 424 题。
• SUM 问题集。第 1 题，第 15 题，第 16 题，第 18 题，第 167 题，第 923 题，第 1074 题。

Problems List in there

Linked List

• 巧妙的构造虚拟头结点。可以使遍历处理逻辑更加统一。
• 灵活使用递归。构造递归条件，使用递归可以巧妙的解题。不过需要注意有些题目不能使用递归，因为递归深度太深会导致超时和栈溢出。
• 链表区间逆序。第 92 题。
• 链表寻找中间节点。第 876 题。链表寻找倒数第 n 个节点。第 19 题。只需要一次遍历就可以得到答案。
• 合并 K 个有序链表。第 21 题，第 23 题。
• 链表归类。第 86 题，第 328 题。
• 链表排序，时间复杂度要求 O(n * log n)，空间复杂度 O(1)。只有一种做法，归并排序，至顶向下归并。第 148 题。
• 判断链表是否存在环，如果有环，输出环的交叉点的下标；判断 2 个链表是否有交叉点，如果有交叉点，输出交叉点。第 141 题，第 142 题，第 160 题。

Problems List in there

Stack

• 括号匹配问题及类似问题。第 20 题，第 921 题，第 1021 题。
• 栈的基本 pop 和 push 操作。第 71 题，第 150 题，第 155 题，第 224 题，第 225 题，第 232 题，第 946 题，第 1047 题。
• 利用栈进行编码问题。第 394 题，第 682 题，第 856 题，第 880 题。
• 单调栈。利用栈维护一个单调递增或者递减的下标数组。第 84 题，第 456 题，第 496 题，第 503 题，第 739 题，第 901 题，第 907 题，第 1019 题。

Problems List in there

Tree

Problems List in there

Dynamic Programming

Problems List in there

Backtracking

• 排列问题 Permutations。第 46 题，第 47 题。第 60 题，第 526 题，第 996 题。
• 组合问题 Combination。第 39 题，第 40 题，第 77 题，第 216 题。
• 排列和组合杂交问题。第 1079 题。
• N 皇后终极解法(二进制解法)。第 51 题，第 52 题。
• 数独问题。第 37 题。
• 四个方向搜索。第 79 题，第 212 题，第 980 题。
• 子集合问题。第 78 题，第 90 题。
• Trie。第 208 题，第 211 题。
• BFS 优化。第 126 题，第 127 题。
• DFS 模板。(只是一个例子，不对应任何题)

func combinationSum2(candidates []int, target int) [][]int {
	if len(candidates) == 0 {
		return [][]int{}
	}
	c, res := []int{}, [][]int{}
	sort.Ints(candidates)
	findcombinationSum2(candidates, target, 0, c, &res)
	return res
}

func findcombinationSum2(nums []int, target, index int, c []int, res *[][]int) {
	if target == 0 {
		b := make([]int, len(c))
		copy(b, c)
		*res = append(*res, b)
		return
	}
	for i := index; i < len(nums); i++ {
		if i > index && nums[i] == nums[i-1] { // 这里是去重的关键逻辑
			continue
		}
		if target >= nums[i] {
			c = append(c, nums[i])
			findcombinationSum2(nums, target-nums[i], i+1, c, res)
			c = c[:len(c)-1]
		}
	}
}

• BFS 模板。(只是一个例子，不对应任何题)

func updateMatrix_BFS(matrix [][]int) [][]int {
	res := make([][]int, len(matrix))
	if len(matrix) == 0 || len(matrix[0]) == 0 {
		return res
	}
	queue := make([][]int, 0)
	for i, _ := range matrix {
		res[i] = make([]int, len(matrix[0]))
		for j, _ := range res[i] {
			if matrix[i][j] == 0 {
				res[i][j] = -1
				queue = append(queue, []int{i, j})
			}
		}
	}
	level := 1
	for len(queue) > 0 {
		size := len(queue)
		for size > 0 {
			size -= 1
			node := queue[0]
			queue = queue[1:]
			i, j := node[0], node[1]
			for _, direction := range [][]int{{-1, 0}, {1, 0}, {0, 1}, {0, -1}} {
				x := i + direction[0]
				y := j + direction[1]
				if x < 0 || x >= len(matrix) || y < 0 || y >= len(matrix[0]) || res[x][y] < 0 || res[x][y] > 0 {
					continue
				}
				res[x][y] = level
				queue = append(queue, []int{x, y})
			}
		}
		level++
	}
	for i, row := range res {
		for j, cell := range row {
			if cell == -1 {
				res[i][j] = 0
			}
		}
	}
	return res
}

Problems List in there

Depth First Search

Problems List in there

Breadth First Search

Problems List in there

Binary Search

• 二分搜索的经典写法。需要注意的三点：
  1. 循环退出条件，注意是 low <= high，而不是 low < high。
  2. mid 的取值，mid := low + (high-low)>>1
  3. low 和 high 的更新。low = mid + 1，high = mid - 1。

func binarySearchMatrix(nums []int, target int) int {
	low, high := 0, len(nums)-1
	for low <= high {
		mid := low + (high-low)>>1
		if nums[mid] == target {
			return mid
		} else if nums[mid] > target {
			high = mid - 1
		} else {
			low = mid + 1
		}
	}
	return -1
}

• 二分搜索的变种写法。有 4 个基本变种:
  1. 查找第一个与 target 相等的元素，时间复杂度 O(logn)
  2. 查找最后一个与 target 相等的元素，时间复杂度 O(logn)
  3. 查找第一个大于等于 target 的元素，时间复杂度 O(logn)
  4. 查找最后一个小于等于 target 的元素，时间复杂度 O(logn)

// 二分查找第一个与 target 相等的元素，时间复杂度 O(logn)
func searchFirstEqualElement(nums []int, target int) int {
	low, high := 0, len(nums)-1
	for low <= high {
		mid := low + ((high - low) >> 1)
		if nums[mid] > target {
			high = mid - 1
		} else if nums[mid] < target {
			low = mid + 1
		} else {
			if (mid == 0) || (nums[mid-1] != target) { // 找到第一个与 target 相等的元素
				return mid
			}
			high = mid - 1
		}
	}
	return -1
}

// 二分查找最后一个与 target 相等的元素，时间复杂度 O(logn)
func searchLastEqualElement(nums []int, target int) int {
	low, high := 0, len(nums)-1
	for low <= high {
		mid := low + ((high - low) >> 1)
		if nums[mid] > target {
			high = mid - 1
		} else if nums[mid] < target {
			low = mid + 1
		} else {
			if (mid == len(nums)-1) || (nums[mid+1] != target) { // 找到最后一个与 target 相等的元素
				return mid
			}
			low = mid + 1
		}
	}
	return -1
}

// 二分查找第一个大于等于 target 的元素，时间复杂度 O(logn)
func searchFirstGreaterElement(nums []int, target int) int {
	low, high := 0, len(nums)-1
	for low <= high {
		mid := low + ((high - low) >> 1)
		if nums[mid] >= target {
			if (mid == 0) || (nums[mid-1] < target) { // 找到第一个大于等于 target 的元素
				return mid
			}
			high = mid - 1
		} else {
			low = mid + 1
		}
	}
	return -1
}

// 二分查找最后一个小于等于 target 的元素，时间复杂度 O(logn)
func searchLastLessElement(nums []int, target int) int {
	low, high := 0, len(nums)-1
	for low <= high {
		mid := low + ((high - low) >> 1)
		if nums[mid] <= target {
			if (mid == len(nums)-1) || (nums[mid+1] > target) { // 找到最后一个小于等于 target 的元素
				return mid
			}
			low = mid + 1
		} else {
			high = mid - 1
		}
	}
	return -1
}

• 在基本有序的数组中用二分搜索。经典解法可以解，变种写法也可以写，常见的题型，在山峰数组中找山峰，在旋转有序数组中找分界点。第 33 题，第 81 题，第 153 题，第 154 题，第 162 题，第 852 题

func peakIndexInMountainArray(A []int) int {
	low, high := 0, len(A)-1
	for low < high {
		mid := low + (high-low)>>1
		// 如果 mid 较大，则左侧存在峰值，high = m，如果 mid + 1 较大，则右侧存在峰值，low = mid + 1
		if A[mid] > A[mid+1] {
			high = mid
		} else {
			low = mid + 1
		}
	}
	return low
}

• max-min 最大值最小化问题。求在最小满足条件的情况下的最大值。第 410 题，第 875 题，第 1011 题，第 1283 题。

Problems List in there

Math

Problems List in there

Hash Table

Problems List in there

Sort

• 深刻的理解多路快排。第 75 题。
• 链表的排序，插入排序(第 147 题)和归并排序(第 148 题)
• 桶排序和基数排序。第 164 题。
• "摆动排序"。第 324 题。
• 两两不相邻的排序。第 767 题，第 1054 题。
• "饼子排序"。第 969 题。

Problems List in there

Bit Manipulation

• 异或的特性。第 136 题，第 268 题，第 389 题，第 421 题，

x ^ 0 = x
x ^ 11111……1111 = ~x
x ^ (~x) = 11111……1111
x ^ x = 0
a ^ b = c  => a ^ c = b  => b ^ c = a (交换律)
a ^ b ^ c = a ^ (b ^ c) = (a ^ b）^ c (结合律)

• 构造特殊 Mask，将特殊位置放 0 或 1。

将 x 最右边的 n 位清零， x & ( ~0 << n )
获取 x 的第 n 位值(0 或者 1)，(x >> n) & 1
获取 x 的第 n 位的幂值，x & (1 << (n - 1))
仅将第 n 位置为 1，x | (1 << n)
仅将第 n 位置为 0，x & (~(1 << n))
将 x 最高位至第 n 位(含)清零，x & ((1 << n) - 1)
将第 n 位至第 0 位(含)清零，x & (~((1 << (n + 1)) - 1)）

• 有特殊意义的 & 位操作运算。第 260 题，第 201 题，第 318 题，第 371 题，第 397 题，第 461 题，第 693 题，

X & 1 == 1 判断是否是奇数(偶数)
X & = (X - 1) 将最低位(LSB)的 1 清零
X & -X 得到最低位(LSB)的 1
X & ~X = 0

Problems List in there

Union Find

• 灵活使用并查集的思想，熟练掌握并查集的模板，模板中有两种并查集的实现方式，一种是路径压缩 + 秩优化的版本，另外一种是计算每个集合中元素的个数 + 最大集合元素个数的版本，这两种版本都有各自使用的地方。能使用第一类并查集模板的题目有：第 128 题，第 130 题，第 547 题，第 684 题，第 721 题，第 765 题，第 778 题，第 839 题，第 924 题，第 928 题，第 947 题，第 952 题，第 959 题，第 990 题。能使用第二类并查集模板的题目有：第 803 题，第 952 题。第 803 题秩优化和统计集合个数这些地方会卡时间，如果不优化，会 TLE。
• 并查集是一种思想，有些题需要灵活使用这种思想，而不是死套模板，如第 399 题，这一题是 stringUnionFind，利用并查集思想实现的。这里每个节点是基于字符串和 map 的，而不是单纯的用 int 节点编号实现的。
• 有些题死套模板反而做不出来，比如第 685 题，这一题不能路径压缩和秩优化，因为题目中涉及到有向图，需要知道节点的前驱节点，如果路径压缩了，这一题就没法做了。这一题不需要路径压缩和秩优化。
• 灵活的抽象题目给的信息，将给定的信息合理的编号，使用并查集解题，并用 map 降低时间复杂度，如第 721 题，第 959 题。
• 关于地图，砖块，网格的题目，可以新建一个特殊节点，将四周边缘的砖块或者网格都 union() 到这个特殊节点上。第 130 题，第 803 题。
• 能用并查集的题目，一般也可以用 DFS 和 BFS 解答，只不过时间复杂度会高一点。

Problems List in there

Sliding Window

• 双指针滑动窗口的经典写法。右指针不断往右移，移动到不能往右移动为止(具体条件根据题目而定)。当右指针到最右边以后，开始挪动左指针，释放窗口左边界。第 3 题，第 76 题，第 209 题，第 424 题，第 438 题，第 567 题，第 713 题，第 763 题，第 845 题，第 881 题，第 904 题，第 978 题，第 992 题，第 1004 题，第 1040 题，第 1052 题。

	left, right := 0, -1

	for left < len(s) {
		if right+1 < len(s) && freq[s[right+1]-'a'] == 0 {
			freq[s[right+1]-'a']++
			right++
		} else {
			freq[s[left]-'a']--
			left++
		}
		result = max(result, right-left+1)
	}

• 滑动窗口经典题。第 239 题，第 480 题。

Problems List in there

Segment Tree

• 线段树的经典数组实现写法。将合并两个节点 pushUp 逻辑抽象出来了，可以实现任意操作(常见的操作有：加法，取 max，min 等等)。第 218 题，第 303 题，第 307 题，第 699 题。
• 计数线段树的经典写法。第 315 题，第 327 题，第 493 题。
• 线段树的树的实现写法。第 715 题，第 732 题。
• 区间懒惰更新。第 218 题，第 699 题。
• 离散化。离散化需要注意一个特殊情况：假如三个区间为 [1,10] [1,4] [6,10]，离散化后 x[1]=1,x[2]=4,x[3]=6,x[4]=10。第一个区间为 [1,4]，第二个区间为 [1,2]，第三个区间为 [3,4]，这样一来，区间一 = 区间二 + 区间三，这和离散前的模型不符，离散前，很明显，区间一 > 区间二 + 区间三。正确的做法是：在相差大于 1 的数间加一个数，例如在上面 1 4 6 10 中间加 5，即可 x[1]=1,x[2]=4,x[3]=5,x[4]=6,x[5]=10。这样处理之后，区间一是 1-5 ，区间二是 1-2 ，区间三是 4-5 。
• 灵活构建线段树。线段树节点可以存储多条信息，合并两个节点的 pushUp 操作也可以是多样的。第 850 题，第 1157 题。

线段树题型从简单到困难:

1. 单点更新:
   HDU 1166 敌兵布阵 update:单点增减 query:区间求和
   HDU 1754 I Hate It update:单点替换 query:区间最值
   HDU 1394 Minimum Inversion Number update:单点增减 query:区间求和
   HDU 2795 Billboard query:区间求最大值的位子(直接把update的操作在query里做了)
2. 区间更新:
   HDU 1698 Just a Hook update:成段替换 (由于只query一次总区间,所以可以直接输出 1 结点的信息)
   POJ 3468 A Simple Problem with Integers update:成段增减 query:区间求和
   POJ 2528 Mayor’s posters 离散化 + update:成段替换 query:简单hash
   POJ 3225 Help with Intervals update:成段替换,区间异或 query:简单hash
3. 区间合并(这类题目会询问区间中满足条件的连续最长区间,所以PushUp的时候需要对左右儿子的区间进行合并):
   POJ 3667 Hotel update:区间替换 query:询问满足条件的最左端点
4. 扫描线(这类题目需要将一些操作排序,然后从左到右用一根扫描线扫过去最典型的就是矩形面积并,周长并等题):
   HDU 1542 Atlantis update:区间增减 query:直接取根节点的值
   HDU 1828 Picture update:区间增减 query:直接取根节点的值

Problems List in there

Binary Indexed Tree

Problems List in there

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