README.md

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. 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
顺序线性表：向量
单链表	1.双链表 2.静态链表 3.对称矩阵 4.稀疏矩阵
栈	广义栈
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
树	1.二叉树 2.并查集 3.Huffman数
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 6.AA树 7.红黑树 8.排序二叉堆 9.Splay树 10.双链树 11.Trie树

算法

一. 目录

#	Title	Solution	Acceptance	Difficulty	Frequency
0001	Two Sum	Go	45.6%	Easy
0002	Add Two Numbers	Go	33.9%	Medium
0003	Longest Substring Without Repeating Characters	Go	30.4%	Medium
0004	Median of Two Sorted Arrays	Go	29.6%	Hard
0005	Longest Palindromic Substring		29.4%	Medium
0006	ZigZag Conversion		36.3%	Medium
0007	Reverse Integer	Go	25.8%	Easy
0008	String to Integer (atoi)		15.4%	Medium
0009	Palindrome Number	Go	48.4%	Easy
0010	Regular Expression Matching		26.8%	Hard
0011	Container With Most Water	Go	50.8%	Medium
0012	Integer to Roman		55.0%	Medium
0013	Roman to Integer	Go	55.7%	Easy
0014	Longest Common Prefix		35.4%	Easy
0015	3Sum	Go	26.8%	Medium
0016	3Sum Closest	Go	46.0%	Medium
0017	Letter Combinations of a Phone Number	Go	46.8%	Medium
0018	4Sum	Go	33.6%	Medium
0019	Remove Nth Node From End of List	Go	35.2%	Medium
0020	Valid Parentheses	Go	38.9%	Easy
0021	Merge Two Sorted Lists	Go	53.5%	Easy
0022	Generate Parentheses	Go	62.6%	Medium
0023	Merge k Sorted Lists	Go	40.2%	Hard
0024	Swap Nodes in Pairs	Go	50.3%	Medium
0025	Reverse Nodes in k-Group	Go	42.0%	Hard
0026	Remove Duplicates from Sorted Array	Go	45.1%	Easy
0027	Remove Element	Go	48.2%	Easy
0028	Implement strStr()	Go	34.5%	Easy
0029	Divide Two Integers	Go	16.4%	Medium
0030	Substring with Concatenation of All Words	Go(是否还有更优解)	25.4%	Hard
0031	Next Permutation		32.6%	Medium
0032	Longest Valid Parentheses		28.4%	Hard
0033	Search in Rotated Sorted Array	Go	34.5%	Medium
0034	Find First and Last Position of Element in Sorted Array	Go	36.1%	Medium
0035	Search Insert Position	Go	42.6%	Easy
0036	Valid Sudoku	Go	48.7%	Medium
0037	Sudoku Solver	Go	43.5%	Hard
0038	Count and Say		44.6%	Easy
0039	Combination Sum	Go	56.0%	Medium
0040	Combination Sum II	Go	48.1%	Medium
0041	First Missing Positive	Go	32.0%	Hard
0042	Trapping Rain Water	Go	48.8%	Hard
0043	Multiply Strings		33.9%	Medium
0044	Wildcard Matching		24.7%	Hard
0045	Jump Game II		30.5%	Hard
0046	Permutations	Go	63.5%	Medium
0047	Permutations II	Go	46.4%	Medium
0048	Rotate Image	Go	56.6%	Medium
0049	Group Anagrams	Go	56.8%	Medium
0050	Pow(x, n)	Go	30.3%	Medium
0051	N-Queens	Go	46.6%	Hard
0052	N-Queens II	Go	57.8%	Hard
0053	Maximum Subarray	Go	46.5%	Easy
0054	Spiral Matrix	Go	34.1%	Medium
0055	Jump Game	Go	34.6%	Medium
0056	Merge Intervals	Go	39.3%	Medium
0057	Insert Interval	Go	33.5%	Hard
0058	Length of Last Word		32.6%	Easy
0059	Spiral Matrix II	Go	53.8%	Medium
0060	Permutation Sequence	Go	38.4%	Hard
0061	Rotate List	Go	30.0%	Medium
0062	Unique Paths	Go	54.1%	Medium
0063	Unique Paths II	Go	34.5%	Medium
0064	Minimum Path Sum	Go	54.4%	Medium
0065	Valid Number		15.3%	Hard
0066	Plus One	Go	43.0%	Easy
0067	Add Binary	Go	45.2%	Easy
0068	Text Justification		27.7%	Hard
0069	Sqrt(x)	Go	33.9%	Easy
0070	Climbing Stairs	Go	47.8%	Easy
0071	Simplify Path	Go	32.6%	Medium
0072	Edit Distance		44.8%	Hard
0073	Set Matrix Zeroes		43.1%	Medium
0074	Search a 2D Matrix	Go	36.5%	Medium
0075	Sort Colors	Go	47.3%	Medium
0076	Minimum Window Substring	Go	34.6%	Hard
0077	Combinations	Go	54.7%	Medium
0078	Subsets	Go	61.9%	Medium
0079	Word Search	Go	35.6%	Medium
0080	Remove Duplicates from Sorted Array II	Go	43.9%	Medium
0081	Search in Rotated Sorted Array II	Go	33.0%	Medium
0082	Remove Duplicates from Sorted List II	Go	36.8%	Medium
0083	Remove Duplicates from Sorted List	Go	45.4%	Easy
0084	Largest Rectangle in Histogram	Go	35.1%	Hard
0085	Maximal Rectangle		37.7%	Hard
0086	Partition List	Go	41.4%	Medium
0087	Scramble String		33.7%	Hard
0088	Merge Sorted Array	Go	39.4%	Easy
0089	Gray Code	Go	49.1%	Medium
0090	Subsets II	Go	47.1%	Medium
0091	Decode Ways	Go	24.6%	Medium
0092	Reverse Linked List II	Go	38.8%	Medium
0093	Restore IP Addresses	Go	35.6%	Medium
0094	Binary Tree Inorder Traversal	Go	63.3%	Medium
0095	Unique Binary Search Trees II	Go	40.6%	Medium
0096	Unique Binary Search Trees	Go	52.9%	Medium
0097	Interleaving String		31.5%	Hard
0098	Validate Binary Search Tree	Go	27.8%	Medium
0099	Recover Binary Search Tree	Go	39.6%	Hard
0100	Same Tree	Go	53.4%	Easy
0101	Symmetric Tree	Go	46.8%	Easy
0102	Binary Tree Level Order Traversal	Go	54.5%	Medium
0103	Binary Tree Zigzag Level Order Traversal	Go	48.3%	Medium
0104	Maximum Depth of Binary Tree	Go	66.0%	Easy
0105	Construct Binary Tree from Preorder and Inorder Traversal	Go	48.8%	Medium
0106	Construct Binary Tree from Inorder and Postorder Traversal	Go	47.1%	Medium
0107	Binary Tree Level Order Traversal II	Go	53.5%	Easy
0108	Convert Sorted Array to Binary Search Tree	Go	57.9%	Easy
0109	Convert Sorted List to Binary Search Tree	Go	47.6%	Medium
0110	Balanced Binary Tree	Go	43.5%	Easy
0111	Minimum Depth of Binary Tree	Go	37.4%	Easy
0112	Path Sum	Go	41.1%	Easy
0113	Path Sum II	Go	46.6%	Medium
0114	Flatten Binary Tree to Linked List	Go	49.2%	Medium
0115	Distinct Subsequences		38.2%	Hard
0116	Populating Next Right Pointers in Each Node		45.2%	Medium
0117	Populating Next Right Pointers in Each Node II		39.1%	Medium
0118	Pascal's Triangle		52.4%	Easy
0119	Pascal's Triangle II		49.0%	Easy
0120	Triangle	Go	44.1%	Medium
0121	Best Time to Buy and Sell Stock	Go	50.4%	Easy
0122	Best Time to Buy and Sell Stock II	Go	56.9%	Easy
0123	Best Time to Buy and Sell Stock III		37.4%	Hard
0124	Binary Tree Maximum Path Sum	Go	34.3%	Hard
0125	Valid Palindrome	Go	36.7%	Easy
0126	Word Ladder II	Go	22.1%	Hard
0127	Word Ladder	Go	29.5%	Medium
0128	Longest Consecutive Sequence	Go	45.1%	Hard
0129	Sum Root to Leaf Numbers	Go	49.0%	Medium
0130	Surrounded Regions	Go	28.1%	Medium
0131	Palindrome Partitioning	Go	47.5%	Medium
0132	Palindrome Partitioning II		30.2%	Hard
0133	Clone Graph		34.7%	Medium
0134	Gas Station		38.5%	Medium
0135	Candy		31.6%	Hard
0136	Single Number	Go	65.5%	Easy
0137	Single Number II	Go	52.4%	Medium
0138	Copy List with Random Pointer		36.3%	Medium
0139	Word Break		40.0%	Medium
0140	Word Break II		32.6%	Hard
0141	Linked List Cycle	Go	41.1%	Easy
0142	Linked List Cycle II	Go	37.3%	Medium
0143	Reorder List	Go	37.0%	Medium
0144	Binary Tree Preorder Traversal	Go	55.6%	Medium
0145	Binary Tree Postorder Traversal	Go	54.9%	Hard
0146	LRU Cache		33.1%	Medium
0147	Insertion Sort List	Go	41.1%	Medium
0148	Sort List	Go	42.3%	Medium
0149	Max Points on a Line		16.9%	Hard
0150	Evaluate Reverse Polish Notation	Go	36.3%	Medium
0151	Reverse Words in a String	Go	21.9%	Medium
0152	Maximum Product Subarray	Go	31.7%	Medium
0153	Find Minimum in Rotated Sorted Array	Go	45.1%	Medium
0154	Find Minimum in Rotated Sorted Array II	Go	41.6%	Hard
0155	Min Stack	Go	44.4%	Easy
0156	Binary Tree Upside Down		55.0%	Medium
0157	Read N Characters Given Read4		34.2%	Easy
0158	Read N Characters Given Read4 II - Call multiple times		33.7%	Hard
0159	Longest Substring with At Most Two Distinct Characters		49.4%	Medium
0160	Intersection of Two Linked Lists	Go	40.5%	Easy
0161	One Edit Distance		32.3%	Medium
0162	Find Peak Element	Go	43.3%	Medium
0163	Missing Ranges		24.3%	Medium
0164	Maximum Gap	Go	35.4%	Hard
0165	Compare Version Numbers		27.4%	Medium
0166	Fraction to Recurring Decimal		21.6%	Medium
0167	Two Sum II - Input array is sorted	Go	54.0%	Easy
0168	Excel Sheet Column Title	Go	31.0%	Easy
0169	Majority Element	Go	58.7%	Easy
0170	Two Sum III - Data structure design		33.5%	Easy
0171	Excel Sheet Column Number	Go	54.6%	Easy
0172	Factorial Trailing Zeroes	Go	37.8%	Easy
0173	Binary Search Tree Iterator	Go	56.5%	Medium
0174	Dungeon Game	Go	32.3%	Hard
0175	Combine Two Tables		60.7%	Easy
0176	Second Highest Salary		31.6%	Easy
0177	Nth Highest Salary		31.3%	Medium
0178	Rank Scores		45.8%	Medium
0179	Largest Number	Go	28.7%	Medium
0180	Consecutive Numbers		39.7%	Medium
0181	Employees Earning More Than Their Managers		56.8%	Easy
0182	Duplicate Emails		62.0%	Easy
0183	Customers Who Never Order		53.4%	Easy
0184	Department Highest Salary		36.6%	Medium
0185	Department Top Three Salaries		34.5%	Hard
0186	Reverse Words in a String II		43.3%	Medium
0187	Repeated DNA Sequences	Go	38.9%	Medium
0188	Best Time to Buy and Sell Stock IV		28.0%	Hard
0189	Rotate Array		34.7%	Easy
0190	Reverse Bits	Go	39.7%	Easy
0191	Number of 1 Bits	Go	49.8%	Easy
0192	Word Frequency		25.8%	Medium
0193	Valid Phone Numbers		25.3%	Easy
0194	Transpose File		24.1%	Medium
0195	Tenth Line		33.0%	Easy
0196	Delete Duplicate Emails		41.0%	Easy
0197	Rising Temperature		38.4%	Easy
0198	House Robber	Go	42.0%	Easy
0199	Binary Tree Right Side View	Go	54.0%	Medium
0200	Number of Islands	Go	46.8%	Medium
0201	Bitwise AND of Numbers Range	Go	39.3%	Medium
0202	Happy Number	Go	50.4%	Easy
0203	Remove Linked List Elements	Go	38.6%	Easy
0204	Count Primes	Go	31.5%	Easy
0205	Isomorphic Strings	Go	39.8%	Easy
0206	Reverse Linked List	Go	62.5%	Easy
0207	Course Schedule	Go	43.1%	Medium
0208	Implement Trie (Prefix Tree)	Go	49.3%	Medium
0209	Minimum Size Subarray Sum	Go	38.1%	Medium
0210	Course Schedule II	Go	40.7%	Medium
0211	Add and Search Word - Data structure design	Go	38.1%	Medium
0212	Word Search II	Go	34.8%	Hard
0213	House Robber II	Go	36.5%	Medium
0214	Shortest Palindrome		29.8%	Hard
0215	Kth Largest Element in an Array	Go	55.3%	Medium
0216	Combination Sum III	Go	56.5%	Medium
0217	Contains Duplicate	Go	56.0%	Easy
0218	The Skyline Problem	Go	34.5%	Hard
0219	Contains Duplicate II	Go	37.7%	Easy
0220	Contains Duplicate III	Go	20.9%	Medium
0221	Maximal Square		37.7%	Medium
0222	Count Complete Tree Nodes	Go	46.7%	Medium
0223	Rectangle Area	Go	37.8%	Medium
0224	Basic Calculator	Go	36.8%	Hard
0225	Implement Stack using Queues	Go	45.1%	Easy
0226	Invert Binary Tree	Go	64.9%	Easy
0227	Basic Calculator II		36.9%	Medium
0228	Summary Ranges		39.5%	Medium
0229	Majority Element II	Go	35.6%	Medium
0230	Kth Smallest Element in a BST	Go	60.2%	Medium
0231	Power of Two	Go	43.7%	Easy
0232	Implement Queue using Stacks	Go	49.5%	Easy
0233	Number of Digit One		31.3%	Hard
0234	Palindrome Linked List	Go	39.2%	Easy
0235	Lowest Common Ancestor of a Binary Search Tree	Go	49.9%	Easy
0236	Lowest Common Ancestor of a Binary Tree	Go	45.6%	Medium
0237	Delete Node in a Linked List	Go	63.7%	Easy
0238	Product of Array Except Self		60.1%	Medium
0239	Sliding Window Maximum	Go	43.0%	Hard
0240	Search a 2D Matrix II	Go	43.1%	Medium
0241	Different Ways to Add Parentheses		55.2%	Medium
0242	Valid Anagram	Go	56.8%	Easy
0243	Shortest Word Distance		61.0%	Easy
0244	Shortest Word Distance II		52.3%	Medium
0245	Shortest Word Distance III		55.3%	Medium
0246	Strobogrammatic Number		45.0%	Easy
0247	Strobogrammatic Number II		47.6%	Medium
0248	Strobogrammatic Number III		39.6%	Hard
0249	Group Shifted Strings		55.0%	Medium
0250	Count Univalue Subtrees		51.9%	Medium
0251	Flatten 2D Vector		45.7%	Medium
0252	Meeting Rooms		54.6%	Easy
0253	Meeting Rooms II		45.7%	Medium
0254	Factor Combinations		46.7%	Medium
0255	Verify Preorder Sequence in Binary Search Tree		45.7%	Medium
0256	Paint House		52.1%	Easy
0257	Binary Tree Paths	Go	51.4%	Easy
0258	Add Digits	Go	57.6%	Easy
0259	3Sum Smaller		47.6%	Medium
0260	Single Number III	Go	64.3%	Medium
0261	Graph Valid Tree		42.2%	Medium
0262	Trips and Users		32.6%	Hard
0263	Ugly Number	Go	41.6%	Easy
0264	Ugly Number II		42.0%	Medium
0265	Paint House II		44.6%	Hard
0266	Palindrome Permutation		61.9%	Easy
0267	Palindrome Permutation II		36.4%	Medium
0268	Missing Number	Go	51.7%	Easy
0269	Alien Dictionary		33.3%	Hard
0270	Closest Binary Search Tree Value		48.1%	Easy
0271	Encode and Decode Strings		31.5%	Medium
0272	Closest Binary Search Tree Value II		50.5%	Hard
0273	Integer to English Words		27.0%	Hard
0274	H-Index	Go	35.9%	Medium
0275	H-Index II	Go	35.9%	Medium
0276	Paint Fence		38.3%	Easy
0277	Find the Celebrity		41.8%	Medium
0278	First Bad Version		35.7%	Easy
0279	Perfect Squares		47.3%	Medium
0280	Wiggle Sort		63.8%	Medium
0281	Zigzag Iterator		58.4%	Medium
0282	Expression Add Operators		35.5%	Hard
0283	Move Zeroes	Go	57.8%	Easy
0284	Peeking Iterator		45.6%	Medium
0285	Inorder Successor in BST		40.3%	Medium
0286	Walls and Gates		54.5%	Medium
0287	Find the Duplicate Number	Go	55.5%	Medium
0288	Unique Word Abbreviation		21.9%	Medium
0289	Game of Life		54.4%	Medium
0290	Word Pattern	Go	37.0%	Easy
0291	Word Pattern II		43.4%	Hard
0292	Nim Game		54.9%	Easy
0293	Flip Game		60.6%	Easy
0294	Flip Game II		50.0%	Medium
0295	Find Median from Data Stream		44.3%	Hard
0296	Best Meeting Point		57.5%	Hard
0297	Serialize and Deserialize Binary Tree		47.4%	Hard
0298	Binary Tree Longest Consecutive Sequence		47.1%	Medium
0299	Bulls and Cows		42.4%	Easy
0300	Longest Increasing Subsequence	Go	42.6%	Medium
0301	Remove Invalid Parentheses		43.3%	Hard
0302	Smallest Rectangle Enclosing Black Pixels		51.6%	Hard
0303	Range Sum Query - Immutable	Go	44.7%	Easy
0304	Range Sum Query 2D - Immutable		38.5%	Medium
0305	Number of Islands II		40.1%	Hard
0306	Additive Number	Go	29.3%	Medium
0307	Range Sum Query - Mutable	Go	34.6%	Medium
0308	Range Sum Query 2D - Mutable		35.6%	Hard
0309	Best Time to Buy and Sell Stock with Cooldown	Go	47.4%	Medium
0310	Minimum Height Trees		32.3%	Medium
0311	Sparse Matrix Multiplication		61.8%	Medium
0312	Burst Balloons		51.7%	Hard
0313	Super Ugly Number		45.0%	Medium
0314	Binary Tree Vertical Order Traversal		45.2%	Medium
0315	Count of Smaller Numbers After Self	Go	41.5%	Hard
0316	Remove Duplicate Letters		35.8%	Hard
0317	Shortest Distance from All Buildings		41.4%	Hard
0318	Maximum Product of Word Lengths	Go	51.2%	Medium
0319	Bulb Switcher		45.4%	Medium
0320	Generalized Abbreviation		52.0%	Medium
0321	Create Maximum Number		27.0%	Hard
0322	Coin Change	Go	35.4%	Medium
0323	Number of Connected Components in an Undirected Graph		56.0%	Medium
0324	Wiggle Sort II	Go	29.9%	Medium
0325	Maximum Size Subarray Sum Equals k		46.8%	Medium
0326	Power of Three	Go	42.1%	Easy
0327	Count of Range Sum	Go	35.1%	Hard
0328	Odd Even Linked List	Go	55.7%	Medium
0329	Longest Increasing Path in a Matrix	Go	43.4%	Hard
0330	Patching Array		34.5%	Hard
0331	Verify Preorder Serialization of a Binary Tree	Go	40.4%	Medium
0332	Reconstruct Itinerary		36.7%	Medium
0333	Largest BST Subtree		35.8%	Medium
0334	Increasing Triplet Subsequence		40.0%	Medium
0335	Self Crossing		28.0%	Hard
0336	Palindrome Pairs		33.7%	Hard
0337	House Robber III	Go	50.6%	Medium
0338	Counting Bits	Go	69.5%	Medium
0339	Nested List Weight Sum		73.9%	Easy
0340	Longest Substring with At Most K Distinct Characters		44.0%	Hard
0341	Flatten Nested List Iterator		52.9%	Medium
0342	Power of Four	Go	41.7%	Easy
0343	Integer Break	Go	50.4%	Medium
0344	Reverse String	Go	68.5%	Easy
0345	Reverse Vowels of a String	Go	44.2%	Easy
0346	Moving Average from Data Stream		70.9%	Easy
0347	Top K Frequent Elements	Go	61.2%	Medium
0348	Design Tic-Tac-Toe		54.3%	Medium
0349	Intersection of Two Arrays	Go	62.5%	Easy
0350	Intersection of Two Arrays II	Go	51.3%	Easy
0351	Android Unlock Patterns		48.4%	Medium
0352	Data Stream as Disjoint Intervals		47.3%	Hard
0353	Design Snake Game		34.1%	Medium
0354	Russian Doll Envelopes	Go	35.6%	Hard
0355	Design Twitter		30.3%	Medium
0356	Line Reflection		31.8%	Medium
0357	Count Numbers with Unique Digits	Go	48.4%	Medium
0358	Rearrange String k Distance Apart		34.9%	Hard
0359	Logger Rate Limiter		70.8%	Easy
0360	Sort Transformed Array		48.8%	Medium
0361	Bomb Enemy		46.0%	Medium
0362	Design Hit Counter		63.6%	Medium
0363	Max Sum of Rectangle No Larger Than K		37.3%	Hard
0364	Nested List Weight Sum II		62.7%	Medium
0365	Water and Jug Problem		30.6%	Medium
0366	Find Leaves of Binary Tree		70.6%	Medium
0367	Valid Perfect Square	Go	41.7%	Easy
0368	Largest Divisible Subset		38.1%	Medium
0369	Plus One Linked List		58.2%	Medium
0370	Range Addition		62.8%	Medium
0371	Sum of Two Integers	Go	50.7%	Medium
0372	Super Pow	Go	36.4%	Medium
0373	Find K Pairs with Smallest Sums	Go	36.7%	Medium
0374	Guess Number Higher or Lower		43.0%	Easy
0375	Guess Number Higher or Lower II		40.3%	Medium
0376	Wiggle Subsequence		39.6%	Medium
0377	Combination Sum IV		45.3%	Medium
0378	Kth Smallest Element in a Sorted Matrix	Go	54.3%	Medium
0379	Design Phone Directory		46.8%	Medium
0380	Insert Delete GetRandom O(1)		47.5%	Medium
0381	Insert Delete GetRandom O(1) - Duplicates allowed		34.1%	Hard
0382	Linked List Random Node		52.1%	Medium
0383	Ransom Note		53.1%	Easy
0384	Shuffle an Array		52.8%	Medium
0385	Mini Parser	Go	33.8%	Medium
0386	Lexicographical Numbers	Go	51.6%	Medium
0387	First Unique Character in a String	Go	53.3%	Easy
0388	Longest Absolute File Path		41.7%	Medium
0389	Find the Difference	Go	55.3%	Easy
0390	Elimination Game		44.5%	Medium
0391	Perfect Rectangle		30.4%	Hard
0392	Is Subsequence	Go	49.2%	Easy
0393	UTF-8 Validation	Go	37.5%	Medium
0394	Decode String	Go	49.9%	Medium
0395	Longest Substring with At Least K Repeating Characters		41.4%	Medium
0396	Rotate Function		36.3%	Medium
0397	Integer Replacement	Go	32.9%	Medium
0398	Random Pick Index		55.9%	Medium
0399	Evaluate Division	Go	51.6%	Medium
0400	Nth Digit		31.7%	Medium
0401	Binary Watch	Go	47.5%	Easy
0402	Remove K Digits	Go	28.4%	Medium
0403	Frog Jump		39.7%	Hard
0404	Sum of Left Leaves	Go	50.9%	Easy
0405	Convert a Number to Hexadecimal	Go	43.9%	Easy
0406	Queue Reconstruction by Height		66.8%	Medium
0407	Trapping Rain Water II		42.4%	Hard
0408	Valid Word Abbreviation		30.6%	Easy
0409	Longest Palindrome	Go	50.3%	Easy
0410	Split Array Largest Sum	Go	44.5%	Hard
0411	Minimum Unique Word Abbreviation		36.3%	Hard
0412	Fizz Buzz	Go	62.3%	Easy
0413	Arithmetic Slices		57.9%	Medium
0414	Third Maximum Number	Go	30.5%	Easy
0415	Add Strings		47.5%	Easy
0416	Partition Equal Subset Sum	Go	43.7%	Medium
0417	Pacific Atlantic Water Flow		41.1%	Medium
0418	Sentence Screen Fitting		32.6%	Medium
0419	Battleships in a Board		70.0%	Medium
0420	Strong Password Checker		14.1%	Hard
0421	Maximum XOR of Two Numbers in an Array	Go	53.5%	Medium
0422	Valid Word Square		37.7%	Easy
0423	Reconstruct Original Digits from English		46.9%	Medium
0424	Longest Repeating Character Replacement	Go	47.0%	Medium
0425	Word Squares		47.6%	Hard
0426	Convert Binary Search Tree to Sorted Doubly Linked List		59.1%	Medium
0427	Construct Quad Tree		61.4%	Medium
0428	Serialize and Deserialize N-ary Tree		59.4%	Hard
0429	N-ary Tree Level Order Traversal		65.0%	Medium
0430	Flatten a Multilevel Doubly Linked List		55.1%	Medium
0431	Encode N-ary Tree to Binary Tree		70.8%	Hard
0432	All O`one Data Structure		32.4%	Hard
0433	Minimum Genetic Mutation	Go	41.8%	Medium
0434	Number of Segments in a String		37.7%	Easy
0435	Non-overlapping Intervals	Go	42.9%	Medium
0436	Find Right Interval	Go	45.4%	Medium
0437	Path Sum III	Go	46.5%	Medium
0438	Find All Anagrams in a String	Go	43.3%	Medium
0439	Ternary Expression Parser		55.9%	Medium
0440	K-th Smallest in Lexicographical Order		29.1%	Hard
0441	Arranging Coins	Go	41.8%	Easy
0442	Find All Duplicates in an Array		67.7%	Medium
0443	String Compression		41.3%	Easy
0444	Sequence Reconstruction		22.2%	Medium
0445	Add Two Numbers II	Go	54.5%	Medium
0446	Arithmetic Slices II - Subsequence		32.7%	Hard
0447	Number of Boomerangs	Go	51.8%	Easy
0448	Find All Numbers Disappeared in an Array	Go	55.9%	Easy
0449	Serialize and Deserialize BST		52.0%	Medium
0450	Delete Node in a BST		43.1%	Medium
0451	Sort Characters By Frequency	Go	63.0%	Medium
0452	Minimum Number of Arrows to Burst Balloons		49.6%	Medium
0453	Minimum Moves to Equal Array Elements	Go	50.2%	Easy
0454	4Sum II	Go	53.1%	Medium
0455	Assign Cookies	Go	49.9%	Easy
0456	132 Pattern	Go	28.9%	Medium
0457	Circular Array Loop	Go	29.4%	Medium
0458	Poor Pigs		47.4%	Hard
0459	Repeated Substring Pattern		42.2%	Easy
0460	LFU Cache		34.2%	Hard
0461	Hamming Distance	Go	72.8%	Easy
0462	Minimum Moves to Equal Array Elements II		53.8%	Medium
0463	Island Perimeter	Go	65.7%	Easy
0464	Can I Win		28.8%	Medium
0465	Optimal Account Balancing		46.8%	Hard
0466	Count The Repetitions		28.2%	Hard
0467	Unique Substrings in Wraparound String		35.6%	Medium
0468	Validate IP Address		24.0%	Medium
0469	Convex Polygon		37.0%	Medium
0470	Implement Rand10() Using Rand7()	Go	46.3%	Medium
0471	Encode String with Shortest Length		47.1%	Hard
0472	Concatenated Words		43.6%	Hard
0473	Matchsticks to Square		37.7%	Medium
0474	Ones and Zeroes	Go	42.8%	Medium
0475	Heaters	Go	33.1%	Easy
0476	Number Complement	Go	64.8%	Easy
0477	Total Hamming Distance	Go	50.5%	Medium
0478	Generate Random Point in a Circle		38.5%	Medium
0479	Largest Palindrome Product		29.0%	Hard
0480	Sliding Window Median	Go	37.2%	Hard
0481	Magical String		47.5%	Medium
0482	License Key Formatting		43.1%	Easy
0483	Smallest Good Base	Go	35.7%	Hard
0484	Find Permutation		60.5%	Medium
0485	Max Consecutive Ones	Go	54.7%	Easy
0486	Predict the Winner		47.9%	Medium
0487	Max Consecutive Ones II		48.5%	Medium
0488	Zuma Game		39.8%	Hard
0489	Robot Room Cleaner		69.7%	Hard
0490	The Maze		51.4%	Medium
0491	Increasing Subsequences	Go	46.1%	Medium
0492	Construct the Rectangle		49.6%	Easy
0493	Reverse Pairs	Go	25.2%	Hard
0494	Target Sum	Go	46.3%	Medium
0495	Teemo Attacking		53.6%	Medium
0496	Next Greater Element I	Go	63.8%	Easy
0497	Random Point in Non-overlapping Rectangles	Go	37.8%	Medium
0498	Diagonal Traverse	Go	48.2%	Medium
0499	The Maze III		41.0%	Hard
0500	Keyboard Row	Go	64.7%	Easy
0501	Find Mode in Binary Search Tree		42.3%	Easy
0502	IPO		40.4%	Hard
0503	Next Greater Element II	Go	56.5%	Medium
0504	Base 7		46.2%	Easy
0505	The Maze II		47.7%	Medium
0506	Relative Ranks		50.5%	Easy
0507	Perfect Number	Go	35.5%	Easy
0508	Most Frequent Subtree Sum	Go	57.9%	Medium
0509	Fibonacci Number	Go	67.2%	Easy
0510	Inorder Successor in BST II		58.0%	Medium
0511	Game Play Analysis I		80.8%	Easy
0512	Game Play Analysis II		55.5%	Easy
0513	Find Bottom Left Tree Value	Go	61.5%	Medium
0514	Freedom Trail		43.0%	Hard
0515	Find Largest Value in Each Tree Row	Go	61.1%	Medium
0516	Longest Palindromic Subsequence		53.2%	Medium
0517	Super Washing Machines		38.3%	Hard
0518	Coin Change 2		50.2%	Medium
0519	Random Flip Matrix		36.7%	Medium
0520	Detect Capital		54.4%	Easy
0521	Longest Uncommon Subsequence I		57.6%	Easy
0522	Longest Uncommon Subsequence II		34.0%	Medium
0523	Continuous Subarray Sum		24.6%	Medium
0524	Longest Word in Dictionary through Deleting	Go	48.4%	Medium
0525	Contiguous Array		42.8%	Medium
0526	Beautiful Arrangement	Go	57.8%	Medium
0527	Word Abbreviation		54.2%	Hard
0528	Random Pick with Weight	Go	43.9%	Medium
0529	Minesweeper	Go	59.1%	Medium
0530	Minimum Absolute Difference in BST		53.7%	Easy
0531	Lonely Pixel I		59.0%	Medium
0532	K-diff Pairs in an Array	Go	31.5%	Easy
0533	Lonely Pixel II		47.9%	Medium
0534	Game Play Analysis III		75.9%	Medium
0535	Encode and Decode TinyURL		79.9%	Medium
0536	Construct Binary Tree from String		48.3%	Medium
0537	Complex Number Multiplication	Go	67.4%	Medium
0538	Convert BST to Greater Tree		55.3%	Easy
0539	Minimum Time Difference		51.5%	Medium
0540	Single Element in a Sorted Array		57.9%	Medium
0541	Reverse String II	Go	48.4%	Easy
0542	01 Matrix	Go	39.8%	Medium
0543	Diameter of Binary Tree		48.4%	Easy
0544	Output Contest Matches		75.2%	Medium
0545	Boundary of Binary Tree		38.9%	Medium
0546	Remove Boxes		42.7%	Hard
0547	Friend Circles	Go	58.5%	Medium
0548	Split Array with Equal Sum		46.4%	Medium
0549	Binary Tree Longest Consecutive Sequence II		47.0%	Medium
0550	Game Play Analysis IV		45.2%	Medium
0551	Student Attendance Record I		46.0%	Easy
0552	Student Attendance Record II		36.7%	Hard
0553	Optimal Division		56.7%	Medium
0554	Brick Wall		50.0%	Medium
0555	Split Concatenated Strings		42.2%	Medium
0556	Next Greater Element III		31.7%	Medium
0557	Reverse Words in a String III	Go	69.8%	Easy
0558	Logical OR of Two Binary Grids Represented as Quad-Trees		44.6%	Medium
0559	Maximum Depth of N-ary Tree		68.6%	Easy
0560	Subarray Sum Equals K		43.8%	Medium
0561	Array Partition I	Go	72.0%	Easy
0562	Longest Line of Consecutive One in Matrix		45.8%	Medium
0563	Binary Tree Tilt	Go	48.7%	Easy
0564	Find the Closest Palindrome		19.7%	Hard
0565	Array Nesting		55.5%	Medium
0566	Reshape the Matrix	Go	60.5%	Easy
0567	Permutation in String	Go	44.4%	Medium
0568	Maximum Vacation Days		40.8%	Hard
0569	Median Employee Salary		57.6%	Hard
0570	Managers with at Least 5 Direct Reports		66.0%	Medium
0571	Find Median Given Frequency of Numbers		44.7%	Hard
0572	Subtree of Another Tree	Go	44.1%	Easy
0573	Squirrel Simulation		55.6%	Medium
0574	Winning Candidate		47.5%	Medium
0575	Distribute Candies	Go	61.4%	Easy
0576	Out of Boundary Paths		35.1%	Medium
0577	Employee Bonus		68.1%	Easy
0578	Get Highest Answer Rate Question		39.3%	Medium
0579	Find Cumulative Salary of an Employee		37.0%	Hard
0580	Count Student Number in Departments		48.7%	Medium
0581	Shortest Unsorted Continuous Subarray		31.1%	Easy
0582	Kill Process		60.8%	Medium
0583	Delete Operation for Two Strings		48.6%	Medium
0584	Find Customer Referee		72.2%	Easy
0585	Investments in 2016		54.7%	Medium
0586	Customer Placing the Largest Number of Orders		72.9%	Easy
0587	Erect the Fence		35.9%	Hard
0588	Design In-Memory File System		45.9%	Hard
0589	N-ary Tree Preorder Traversal		72.0%	Easy
0590	N-ary Tree Postorder Traversal		72.1%	Easy
0591	Tag Validator		34.3%	Hard
0592	Fraction Addition and Subtraction		49.0%	Medium
0593	Valid Square		43.1%	Medium
0594	Longest Harmonious Subsequence	Go	46.6%	Easy
0595	Big Countries		77.3%	Easy
0596	Classes More Than 5 Students		38.0%	Easy
0597	Friend Requests I: Overall Acceptance Rate		40.9%	Easy
0598	Range Addition II	Go	49.6%	Easy
0599	Minimum Index Sum of Two Lists	Go	50.7%	Easy
0600	Non-negative Integers without Consecutive Ones		34.1%	Hard
0601	Human Traffic of Stadium		41.6%	Hard
0602	Friend Requests II: Who Has the Most Friends		53.3%	Medium
0603	Consecutive Available Seats		63.9%	Easy
0604	Design Compressed String Iterator		37.5%	Easy
0605	Can Place Flowers		31.6%	Easy
0606	Construct String from Binary Tree		54.1%	Easy
0607	Sales Person		62.9%	Easy
0608	Tree Node		67.0%	Medium
0609	Find Duplicate File in System		59.5%	Medium
0610	Triangle Judgement		65.9%	Easy
0611	Valid Triangle Number		48.4%	Medium
0612	Shortest Distance in a Plane		59.5%	Medium
0613	Shortest Distance in a Line		77.5%	Easy
0614	Second Degree Follower		30.2%	Medium
0615	Average Salary: Departments VS Company		46.8%	Hard
0616	Add Bold Tag in String		43.0%	Medium
0617	Merge Two Binary Trees		74.1%	Easy
0618	Students Report By Geography		54.8%	Hard
0619	Biggest Single Number		43.1%	Easy
0620	Not Boring Movies		67.5%	Easy
0621	Task Scheduler		50.0%	Medium
0622	Design Circular Queue		43.7%	Medium
0623	Add One Row to Tree		49.7%	Medium
0624	Maximum Distance in Arrays		38.9%	Easy
0625	Minimum Factorization		32.8%	Medium
0626	Exchange Seats		62.2%	Medium
0627	Swap Salary		75.2%	Easy
0628	Maximum Product of Three Numbers	Go	47.1%	Easy
0629	K Inverse Pairs Array		31.1%	Hard
0630	Course Schedule III		33.5%	Hard
0631	Design Excel Sum Formula		31.5%	Hard
0632	Smallest Range Covering Elements from K Lists	Go	52.4%	Hard
0633	Sum of Square Numbers	Go	32.2%	Easy
0634	Find the Derangement of An Array		40.1%	Medium
0635	Design Log Storage System		58.6%	Medium
0636	Exclusive Time of Functions	Go	52.0%	Medium
0637	Average of Levels in Binary Tree	Go	63.0%	Easy
0638	Shopping Offers	Go	51.5%	Medium
0639	Decode Ways II		26.6%	Hard
0640	Solve the Equation		42.0%	Medium
0641	Design Circular Deque		52.7%	Medium
0642	Design Search Autocomplete System		44.6%	Hard
0643	Maximum Average Subarray I		41.5%	Easy
0644	Maximum Average Subarray II		32.0%	Hard
0645	Set Mismatch	Go	42.1%	Easy
0646	Maximum Length of Pair Chain		51.8%	Medium
0647	Palindromic Substrings		60.6%	Medium
0648	Replace Words	Go	56.5%	Medium
0649	Dota2 Senate		39.2%	Medium
0650	2 Keys Keyboard		49.2%	Medium
0651	4 Keys Keyboard		52.4%	Medium
0652	Find Duplicate Subtrees		50.1%	Medium
0653	Two Sum IV - Input is a BST	Go	55.5%	Easy
0654	Maximum Binary Tree		79.9%	Medium
0655	Print Binary Tree		55.0%	Medium
0656	Coin Path		29.0%	Hard
0657	Robot Return to Origin		73.5%	Easy
0658	Find K Closest Elements	Go	40.9%	Medium
0659	Split Array into Consecutive Subsequences		43.7%	Medium
0660	Remove 9		53.3%	Hard
0661	Image Smoother	Go	51.5%	Easy
0662	Maximum Width of Binary Tree	Go	41.1%	Medium
0663	Equal Tree Partition		39.5%	Medium
0664	Strange Printer		40.2%	Hard
0665	Non-decreasing Array		19.5%	Easy
0666	Path Sum IV		54.7%	Medium
0667	Beautiful Arrangement II		54.2%	Medium
0668	Kth Smallest Number in Multiplication Table	Go	45.6%	Hard
0669	Trim a Binary Search Tree		63.0%	Easy
0670	Maximum Swap		43.6%	Medium
0671	Second Minimum Node In a Binary Tree		42.7%	Easy
0672	Bulb Switcher II		50.9%	Medium
0673	Number of Longest Increasing Subsequence		35.7%	Medium
0674	Longest Continuous Increasing Subsequence		45.9%	Easy
0675	Cut Off Trees for Golf Event		34.6%	Hard
0676	Implement Magic Dictionary	Go	54.5%	Medium
0677	Map Sum Pairs		53.5%	Medium
0678	Valid Parenthesis String		31.0%	Medium
0679	24 Game		46.4%	Hard
0680	Valid Palindrome II		36.6%	Easy
0681	Next Closest Time		45.0%	Medium
0682	Baseball Game	Go	63.7%	Easy
0683	K Empty Slots		35.7%	Hard
0684	Redundant Connection	Go	57.3%	Medium
0685	Redundant Connection II	Go	32.4%	Hard
0686	Repeated String Match		32.3%	Easy
0687	Longest Univalue Path		36.2%	Easy
0688	Knight Probability in Chessboard		48.9%	Medium
0689	Maximum Sum of 3 Non-Overlapping Subarrays		46.3%	Hard
0690	Employee Importance		57.3%	Easy
0691	Stickers to Spell Word		43.0%	Hard
0692	Top K Frequent Words		51.8%	Medium
0693	Binary Number with Alternating Bits	Go	59.4%	Easy
0694	Number of Distinct Islands		56.0%	Medium
0695	Max Area of Island	Go	62.7%	Medium
0696	Count Binary Substrings		56.0%	Easy
0697	Degree of an Array	Go	53.8%	Easy
0698	Partition to K Equal Sum Subsets		44.9%	Medium
0699	Falling Squares	Go	41.8%	Hard
0700	Search in a Binary Search Tree		73.1%	Easy
0701	Insert into a Binary Search Tree		77.8%	Medium
0702	Search in a Sorted Array of Unknown Size		66.7%	Medium
0703	Kth Largest Element in a Stream		49.7%	Easy
0704	Binary Search	Go	52.1%	Easy
0705	Design HashSet	Go	64.3%	Easy
0706	Design HashMap	Go	61.3%	Easy
0707	Design Linked List	Go	24.5%	Medium
0708	Insert into a Sorted Circular Linked List		31.6%	Medium
0709	To Lower Case		79.3%	Easy
0710	Random Pick with Blacklist	Go	32.4%	Hard
0711	Number of Distinct Islands II		47.3%	Hard
0712	Minimum ASCII Delete Sum for Two Strings		58.5%	Medium
0713	Subarray Product Less Than K	Go	39.1%	Medium
0714	Best Time to Buy and Sell Stock with Transaction Fee	Go	54.7%	Medium
0715	Range Module	Go	38.5%	Hard
0716	Max Stack		42.6%	Easy
0717	1-bit and 2-bit Characters	Go	48.8%	Easy
0718	Maximum Length of Repeated Subarray	Go	49.3%	Medium
0719	Find K-th Smallest Pair Distance	Go	31.5%	Hard
0720	Longest Word in Dictionary	Go	48.2%	Easy
0721	Accounts Merge	Go	48.7%	Medium
0722	Remove Comments		34.6%	Medium
0723	Candy Crush		69.3%	Medium
0724	Find Pivot Index		44.0%	Easy
0725	Split Linked List in Parts	Go	52.1%	Medium
0726	Number of Atoms	Go	48.9%	Hard
0727	Minimum Window Subsequence		41.8%	Hard
0728	Self Dividing Numbers		74.3%	Easy
0729	My Calendar I	Go	51.8%	Medium
0730	Count Different Palindromic Subsequences		41.7%	Hard
0731	My Calendar II		49.1%	Medium
0732	My Calendar III	Go	59.9%	Hard
0733	Flood Fill	Go	55.3%	Easy
0734	Sentence Similarity		42.1%	Easy
0735	Asteroid Collision	Go	41.1%	Medium
0736	Parse Lisp Expression		47.5%	Hard
0737	Sentence Similarity II		45.8%	Medium
0738	Monotone Increasing Digits		44.3%	Medium
0739	Daily Temperatures	Go	63.3%	Medium
0740	Delete and Earn		48.6%	Medium
0741	Cherry Pickup		33.9%	Hard
0742	Closest Leaf in a Binary Tree		43.5%	Medium
0743	Network Delay Time		44.9%	Medium
0744	Find Smallest Letter Greater Than Target	Go	45.4%	Easy
0745	Prefix and Suffix Search	Go	34.1%	Hard
0746	Min Cost Climbing Stairs	Go	50.3%	Easy
0747	Largest Number At Least Twice of Others		42.0%	Easy
0748	Shortest Completing Word	Go	56.7%	Easy
0749	Contain Virus		44.5%	Hard
0750	Number Of Corner Rectangles		66.4%	Medium
0751	IP to CIDR		61.8%	Medium
0752	Open the Lock		51.8%	Medium
0753	Cracking the Safe	Go	50.5%	Hard
0754	Reach a Number		34.7%	Medium
0755	Pour Water		43.3%	Medium
0756	Pyramid Transition Matrix	Go	54.6%	Medium
0757	Set Intersection Size At Least Two		40.1%	Hard
0758	Bold Words in String		45.9%	Easy
0759	Employee Free Time		66.2%	Hard
0760	Find Anagram Mappings		81.1%	Easy
0761	Special Binary String		54.7%	Hard
0762	Prime Number of Set Bits in Binary Representation	Go	63.2%	Easy
0763	Partition Labels	Go	76.0%	Medium
0764	Largest Plus Sign		46.0%	Medium
0765	Couples Holding Hands	Go	54.3%	Hard
0766	Toeplitz Matrix	Go	65.0%	Easy
0767	Reorganize String	Go	48.7%	Medium
0768	Max Chunks To Make Sorted II		48.7%	Hard
0769	Max Chunks To Make Sorted		54.7%	Medium
0770	Basic Calculator IV		47.9%	Hard
0771	Jewels and Stones	Go	86.3%	Easy
0772	Basic Calculator III		41.2%	Hard
0773	Sliding Puzzle		59.3%	Hard
0774	Minimize Max Distance to Gas Station		46.9%	Hard
0775	Global and Local Inversions		42.1%	Medium
0776	Split BST		55.8%	Medium
0777	Swap Adjacent in LR String		34.8%	Medium
0778	Swim in Rising Water	Go	53.0%	Hard
0779	K-th Symbol in Grammar		37.2%	Medium
0780	Reaching Points		29.3%	Hard
0781	Rabbits in Forest	Go	54.5%	Medium
0782	Transform to Chessboard		42.8%	Hard
0783	Minimum Distance Between BST Nodes		52.6%	Easy
0784	Letter Case Permutation	Go	64.6%	Medium
0785	Is Graph Bipartite?		47.5%	Medium
0786	K-th Smallest Prime Fraction	Go	41.0%	Hard
0787	Cheapest Flights Within K Stops		39.3%	Medium
0788	Rotated Digits		57.1%	Easy
0789	Escape The Ghosts		57.4%	Medium
0790	Domino and Tromino Tiling		39.2%	Medium
0791	Custom Sort String		65.7%	Medium
0792	Number of Matching Subsequences		47.4%	Medium
0793	Preimage Size of Factorial Zeroes Function	Go	40.2%	Hard
0794	Valid Tic-Tac-Toe State		32.6%	Medium
0795	Number of Subarrays with Bounded Maximum		46.3%	Medium
0796	Rotate String		49.6%	Easy
0797	All Paths From Source to Target		77.9%	Medium
0798	Smallest Rotation with Highest Score		44.1%	Hard
0799	Champagne Tower		35.7%	Medium
0800	Similar RGB Color		61.4%	Easy
0801	Minimum Swaps To Make Sequences Increasing		38.9%	Medium
0802	Find Eventual Safe States	Go	48.9%	Medium
0803	Bricks Falling When Hit	Go	30.8%	Hard
0804	Unique Morse Code Words		77.0%	Easy
0805	Split Array With Same Average		26.3%	Hard
0806	Number of Lines To Write String		64.9%	Easy
0807	Max Increase to Keep City Skyline		83.7%	Medium
0808	Soup Servings		39.9%	Medium
0809	Expressive Words		47.0%	Medium
0810	Chalkboard XOR Game		48.2%	Hard
0811	Subdomain Visit Count	Go	69.8%	Easy
0812	Largest Triangle Area	Go	58.3%	Easy
0813	Largest Sum of Averages		49.9%	Medium
0814	Binary Tree Pruning		74.5%	Medium
0815	Bus Routes	Go	42.6%	Hard
0816	Ambiguous Coordinates		47.2%	Medium
0817	Linked List Components	Go	57.3%	Medium
0818	Race Car		39.0%	Hard
0819	Most Common Word	Go	44.8%	Easy
0820	Short Encoding of Words		50.7%	Medium
0821	Shortest Distance to a Character		66.9%	Easy
0822	Card Flipping Game		42.9%	Medium
0823	Binary Trees With Factors		35.8%	Medium
0824	Goat Latin		63.3%	Easy
0825	Friends Of Appropriate Ages		42.6%	Medium
0826	Most Profit Assigning Work	Go	38.5%	Medium
0827	Making A Large Island		45.6%	Hard
0828	Count Unique Characters of All Substrings of a Given String	Go	45.1%	Hard
0829	Consecutive Numbers Sum		37.4%	Hard
0830	Positions of Large Groups		49.6%	Easy
0831	Masking Personal Information		44.1%	Medium
0832	Flipping an Image	Go	76.2%	Easy
0833	Find And Replace in String		50.4%	Medium
0834	Sum of Distances in Tree	Go	43.7%	Hard
0835	Image Overlap		58.5%	Medium
0836	Rectangle Overlap	Go	48.6%	Easy
0837	New 21 Game		34.6%	Medium
0838	Push Dominoes	Go	48.4%	Medium
0839	Similar String Groups	Go	38.6%	Hard
0840	Magic Squares In Grid		37.3%	Easy
0841	Keys and Rooms	Go	64.3%	Medium
0842	Split Array into Fibonacci Sequence	Go	36.3%	Medium
0843	Guess the Word		46.1%	Hard
0844	Backspace String Compare	Go	46.4%	Easy
0845	Longest Mountain in Array	Go	37.2%	Medium
0846	Hand of Straights		54.2%	Medium
0847	Shortest Path Visiting All Nodes		52.0%	Hard
0848	Shifting Letters		44.6%	Medium
0849	Maximize Distance to Closest Person		42.6%	Easy
0850	Rectangle Area II	Go	47.5%	Hard
0851	Loud and Rich	Go	51.6%	Medium
0852	Peak Index in a Mountain Array	Go	71.6%	Easy
0853	Car Fleet	Go	42.4%	Medium
0854	K-Similar Strings		38.2%	Hard
0855	Exam Room		43.1%	Medium
0856	Score of Parentheses	Go	60.5%	Medium
0857	Minimum Cost to Hire K Workers		49.6%	Hard
0858	Mirror Reflection		53.7%	Medium
0859	Buddy Strings		27.4%	Easy
0860	Lemonade Change		51.6%	Easy
0861	Score After Flipping Matrix		72.8%	Medium
0862	Shortest Subarray with Sum at Least K	Go	24.6%	Hard
0863	All Nodes Distance K in Binary Tree	Go	55.3%	Medium
0864	Shortest Path to Get All Keys	Go	40.1%	Hard
0865	Smallest Subtree with all the Deepest Nodes		60.8%	Medium
0866	Prime Palindrome		24.9%	Medium
0867	Transpose Matrix	Go	62.8%	Easy
0868	Binary Gap		60.6%	Easy
0869	Reordered Power of 2		53.3%	Medium
0870	Advantage Shuffle		45.6%	Medium
0871	Minimum Number of Refueling Stops		31.4%	Hard
0872	Leaf-Similar Trees	Go	64.5%	Easy
0873	Length of Longest Fibonacci Subsequence		48.0%	Medium
0874	Walking Robot Simulation		35.3%	Easy
0875	Koko Eating Bananas	Go	52.1%	Medium
0876	Middle of the Linked List	Go	68.4%	Easy
0877	Stone Game		64.8%	Medium
0878	Nth Magical Number	Go	28.4%	Hard
0879	Profitable Schemes		39.7%	Hard
0880	Decoded String at Index	Go	24.3%	Medium
0881	Boats to Save People	Go	46.8%	Medium
0882	Reachable Nodes In Subdivided Graph		41.3%	Hard
0883	Projection Area of 3D Shapes		67.7%	Easy
0884	Uncommon Words from Two Sentences	Go	63.3%	Easy
0885	Spiral Matrix III	Go	69.3%	Medium
0886	Possible Bipartition		44.1%	Medium
0887	Super Egg Drop	Go	27.0%	Hard
0888	Fair Candy Swap	Go	58.3%	Easy
0889	Construct Binary Tree from Preorder and Postorder Traversal		66.1%	Medium
0890	Find and Replace Pattern		73.4%	Medium
0891	Sum of Subsequence Widths	Go	31.9%	Hard
0892	Surface Area of 3D Shapes	Go	58.9%	Easy
0893	Groups of Special-Equivalent Strings		66.5%	Easy
0894	All Possible Full Binary Trees		75.2%	Medium
0895	Maximum Frequency Stack	Go	60.6%	Hard
0896	Monotonic Array	Go	57.9%	Easy
0897	Increasing Order Search Tree	Go	70.7%	Easy
0898	Bitwise ORs of Subarrays	Go	34.8%	Medium
0899	Orderly Queue		52.2%	Hard
0900	RLE Iterator		53.5%	Medium
0901	Online Stock Span	Go	60.1%	Medium
0902	Numbers At Most N Given Digit Set		31.5%	Hard
0903	Valid Permutations for DI Sequence		49.6%	Hard
0904	Fruit Into Baskets	Go	42.5%	Medium
0905	Sort Array By Parity		74.0%	Easy
0906	Super Palindromes		32.7%	Hard
0907	Sum of Subarray Minimums	Go	32.3%	Medium
0908	Smallest Range I		65.8%	Easy
0909	Snakes and Ladders		38.4%	Medium
0910	Smallest Range II		26.6%	Medium
0911	Online Election	Go	50.4%	Medium
0912	Sort an Array		63.8%	Medium
0913	Cat and Mouse		31.3%	Hard
0914	X of a Kind in a Deck of Cards	Go	34.9%	Easy
0915	Partition Array into Disjoint Intervals		45.3%	Medium
0916	Word Subsets		47.8%	Medium
0917	Reverse Only Letters		57.9%	Easy
0918	Maximum Sum Circular Subarray	Go	33.6%	Medium
0919	Complete Binary Tree Inserter		57.3%	Medium
0920	Number of Music Playlists	Go	46.5%	Hard
0921	Minimum Add to Make Parentheses Valid	Go	73.6%	Medium
0922	Sort Array By Parity II	Go	69.2%	Easy
0923	3Sum With Multiplicity	Go	35.7%	Medium
0924	Minimize Malware Spread	Go	42.0%	Hard
0925	Long Pressed Name	Go	40.6%	Easy
0926	Flip String to Monotone Increasing		52.3%	Medium
0927	Three Equal Parts	Go	33.6%	Hard
0928	Minimize Malware Spread II	Go	40.5%	Hard
0929	Unique Email Addresses		67.4%	Easy
0930	Binary Subarrays With Sum	Go	43.0%	Medium
0931	Minimum Falling Path Sum		62.4%	Medium
0932	Beautiful Array		58.3%	Medium
0933	Number of Recent Calls	Go	71.9%	Easy
0934	Shortest Bridge		48.1%	Medium
0935	Knight Dialer		45.1%	Medium
0936	Stamping The Sequence		42.8%	Hard
0937	Reorder Data in Log Files		54.4%	Easy
0938	Range Sum of BST		81.3%	Easy
0939	Minimum Area Rectangle		51.8%	Medium
0940	Distinct Subsequences II		41.4%	Hard
0941	Valid Mountain Array		33.3%	Easy
0942	DI String Match	Go	72.6%	Easy
0943	Find the Shortest Superstring		42.8%	Hard
0944	Delete Columns to Make Sorted		70.3%	Easy
0945	Minimum Increment to Make Array Unique		46.3%	Medium
0946	Validate Stack Sequences	Go	61.8%	Medium
0947	Most Stones Removed with Same Row or Column	Go	55.3%	Medium
0948	Bag of Tokens		40.8%	Medium
0949	Largest Time for Given Digits	Go	35.9%	Easy
0950	Reveal Cards In Increasing Order		74.6%	Medium
0951	Flip Equivalent Binary Trees		65.7%	Medium
0952	Largest Component Size by Common Factor	Go	30.3%	Hard
0953	Verifying an Alien Dictionary	Go	54.1%	Easy
0954	Array of Doubled Pairs		35.6%	Medium
0955	Delete Columns to Make Sorted II		33.2%	Medium
0956	Tallest Billboard		39.7%	Hard
0957	Prison Cells After N Days		40.7%	Medium
0958	Check Completeness of a Binary Tree		52.0%	Medium
0959	Regions Cut By Slashes	Go	66.1%	Medium
0960	Delete Columns to Make Sorted III		53.6%	Hard
0961	N-Repeated Element in Size 2N Array	Go	73.7%	Easy
0962	Maximum Width Ramp		45.3%	Medium
0963	Minimum Area Rectangle II		50.8%	Medium
0964	Least Operators to Express Number		43.7%	Hard
0965	Univalued Binary Tree		67.7%	Easy
0966	Vowel Spellchecker		47.2%	Medium
0967	Numbers With Same Consecutive Differences		39.4%	Medium
0968	Binary Tree Cameras	Go	37.5%	Hard
0969	Pancake Sorting	Go	67.5%	Medium
0970	Powerful Integers	Go	39.8%	Easy
0971	Flip Binary Tree To Match Preorder Traversal		45.6%	Medium
0972	Equal Rational Numbers		41.6%	Hard
0973	K Closest Points to Origin	Go	63.8%	Medium
0974	Subarray Sums Divisible by K		48.9%	Medium
0975	Odd Even Jump		42.3%	Hard
0976	Largest Perimeter Triangle	Go	57.6%	Easy
0977	Squares of a Sorted Array	Go	72.2%	Easy
0978	Longest Turbulent Subarray	Go	46.6%	Medium
0979	Distribute Coins in Binary Tree	Go	68.8%	Medium
0980	Unique Paths III	Go	73.3%	Hard
0981	Time Based Key-Value Store	Go	53.1%	Medium
0982	Triples with Bitwise AND Equal To Zero		55.5%	Hard
0983	Minimum Cost For Tickets		60.5%	Medium
0984	String Without AAA or BBB	Go	37.7%	Medium
0985	Sum of Even Numbers After Queries	Go	61.3%	Easy
0986	Interval List Intersections	Go	67.3%	Medium
0987	Vertical Order Traversal of a Binary Tree		36.6%	Medium
0988	Smallest String Starting From Leaf		46.0%	Medium
0989	Add to Array-Form of Integer		44.2%	Easy
0990	Satisfiability of Equality Equations	Go	44.9%	Medium
0991	Broken Calculator		45.5%	Medium
0992	Subarrays with K Different Integers	Go	48.6%	Hard
0993	Cousins in Binary Tree	Go	52.0%	Easy
0994	Rotting Oranges		47.8%	Medium
0995	Minimum Number of K Consecutive Bit Flips	Go	46.8%	Hard
0996	Number of Squareful Arrays	Go	47.9%	Hard
0997	Find the Town Judge		50.1%	Easy
0998	Maximum Binary Tree II		62.9%	Medium
0999	Available Captures for Rook	Go	66.7%	Easy
1000	Minimum Cost to Merge Stones		39.6%	Hard
1001	Grid Illumination		35.9%	Hard
1002	Find Common Characters	Go	67.7%	Easy
1003	Check If Word Is Valid After Substitutions	Go	55.3%	Medium
1004	Max Consecutive Ones III	Go	59.1%	Medium
1005	Maximize Sum Of Array After K Negations	Go	51.3%	Easy
1006	Clumsy Factorial		53.3%	Medium
1007	Minimum Domino Rotations For Equal Row		50.0%	Medium
1008	Construct Binary Search Tree from Preorder Traversal		78.4%	Medium
1009	Complement of Base 10 Integer		59.6%	Easy
1010	Pairs of Songs With Total Durations Divisible by 60		47.4%	Easy
1011	Capacity To Ship Packages Within D Days	Go	58.1%	Medium
1012	Numbers With Repeated Digits		37.5%	Hard
1013	Partition Array Into Three Parts With Equal Sum		51.8%	Easy
1014	Best Sightseeing Pair		52.5%	Medium
1015	Smallest Integer Divisible by K		32.1%	Medium
1016	Binary String With Substrings Representing 1 To N		58.9%	Medium
1017	Convert to Base -2	Go	59.0%	Medium
1018	Binary Prefix Divisible By 5		47.7%	Easy
1019	Next Greater Node In Linked List	Go	57.4%	Medium
1020	Number of Enclaves	Go	57.7%	Medium
1021	Remove Outermost Parentheses	Go	77.9%	Easy
1022	Sum of Root To Leaf Binary Numbers		67.2%	Easy
1023	Camelcase Matching		57.0%	Medium
1024	Video Stitching		49.2%	Medium
1025	Divisor Game	Go	66.3%	Easy
1026	Maximum Difference Between Node and Ancestor	Go	65.9%	Medium
1027	Longest Arithmetic Sequence		53.5%	Medium
1028	Recover a Tree From Preorder Traversal	Go	69.9%	Hard
1029	Two City Scheduling		56.1%	Easy
1030	Matrix Cells in Distance Order	Go	65.7%	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays		57.8%	Medium
1032	Stream of Characters		48.3%	Hard
1033	Moving Stones Until Consecutive		41.7%	Easy
1034	Coloring A Border		44.7%	Medium
1035	Uncrossed Lines		56.1%	Medium
1036	Escape a Large Maze		35.4%	Hard
1037	Valid Boomerang	Go	37.9%	Easy
1038	Binary Search Tree to Greater Sum Tree		80.8%	Medium
1039	Minimum Score Triangulation of Polygon		49.1%	Medium
1040	Moving Stones Until Consecutive II	Go	52.9%	Medium
1041	Robot Bounded In Circle		49.5%	Medium
1042	Flower Planting With No Adjacent		48.5%	Easy
1043	Partition Array for Maximum Sum		65.1%	Medium
1044	Longest Duplicate Substring		32.0%	Hard
1045	Customers Who Bought All Products		67.8%	Medium
1046	Last Stone Weight		62.2%	Easy
1047	Remove All Adjacent Duplicates In String	Go	68.5%	Easy
1048	Longest String Chain		54.7%	Medium
1049	Last Stone Weight II	Go	44.1%	Medium
1050	Actors and Directors Who Cooperated At Least Three Times		71.7%	Easy
1051	Height Checker	Go	71.1%	Easy
1052	Grumpy Bookstore Owner	Go	55.4%	Medium
1053	Previous Permutation With One Swap		48.5%	Medium
1054	Distant Barcodes	Go	43.2%	Medium
1055	Shortest Way to Form String		56.9%	Medium
1056	Confusing Number		48.7%	Easy
1057	Campus Bikes		57.7%	Medium
1058	Minimize Rounding Error to Meet Target		41.7%	Medium
1059	All Paths from Source Lead to Destination		44.7%	Medium
1060	Missing Element in Sorted Array		54.5%	Medium
1061	Lexicographically Smallest Equivalent String		65.2%	Medium
1062	Longest Repeating Substring		57.2%	Medium
1063	Number of Valid Subarrays		71.1%	Hard
1064	Fixed Point		66.5%	Easy
1065	Index Pairs of a String		60.6%	Easy
1066	Campus Bikes II		54.2%	Medium
1067	Digit Count in Range		40.0%	Hard
1068	Product Sales Analysis I		83.1%	Easy
1069	Product Sales Analysis II		82.9%	Easy
1070	Product Sales Analysis III		48.9%	Medium
1071	Greatest Common Divisor of Strings		53.0%	Easy
1072	Flip Columns For Maximum Number of Equal Rows		60.8%	Medium
1073	Adding Two Negabinary Numbers	Go	34.0%	Medium
1074	Number of Submatrices That Sum to Target	Go	59.3%	Hard
1075	Project Employees I		64.9%	Easy
1076	Project Employees II		53.7%	Easy
1077	Project Employees III		75.4%	Medium
1078	Occurrences After Bigram	Go	64.7%	Easy
1079	Letter Tile Possibilities	Go	75.4%	Medium
1080	Insufficient Nodes in Root to Leaf Paths		49.3%	Medium
1081	Smallest Subsequence of Distinct Characters		50.4%	Medium
1082	Sales Analysis I		71.7%	Easy
1083	Sales Analysis II		50.6%	Easy
1084	Sales Analysis III		54.2%	Easy
1085	Sum of Digits in the Minimum Number		74.6%	Easy
1086	High Five		79.6%	Easy
1087	Brace Expansion		62.7%	Medium
1088	Confusing Number II		43.9%	Hard
1089	Duplicate Zeros	Go	53.0%	Easy
1090	Largest Values From Labels		58.9%	Medium
1091	Shortest Path in Binary Matrix		38.2%	Medium
1092	Shortest Common Supersequence		51.6%	Hard
1093	Statistics from a Large Sample	Go	48.2%	Medium
1094	Car Pooling		56.7%	Medium
1095	Find in Mountain Array		35.7%	Hard
1096	Brace Expansion II		62.1%	Hard
1097	Game Play Analysis V		54.4%	Hard
1098	Unpopular Books		44.4%	Medium
1099	Two Sum Less Than K		60.6%	Easy
1100	Find K-Length Substrings With No Repeated Characters		72.7%	Medium
1101	The Earliest Moment When Everyone Become Friends		66.2%	Medium
1102	Path With Maximum Minimum Value		49.2%	Medium
1103	Distribute Candies to People		60.5%	Easy
1104	Path In Zigzag Labelled Binary Tree		72.0%	Medium
1105	Filling Bookcase Shelves	Go	58.1%	Medium
1106	Parsing A Boolean Expression		58.5%	Hard
1107	New Users Daily Count		45.1%	Medium
1108	Defanging an IP Address	Go	87.5%	Easy
1109	Corporate Flight Bookings		52.8%	Medium
1110	Delete Nodes And Return Forest	Go	67.0%	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	Go	70.4%	Medium
1112	Highest Grade For Each Student		69.4%	Medium
1113	Reported Posts		64.1%	Easy
1114	Print in Order		65.7%	Easy
1115	Print FooBar Alternately		58.5%	Medium
1116	Print Zero Even Odd		56.0%	Medium
1117	Building H2O		52.6%	Medium
1118	Number of Days in a Month		57.4%	Easy
1119	Remove Vowels from a String		89.9%	Easy
1120	Maximum Average Subtree		62.0%	Medium
1121	Divide Array Into Increasing Sequences		56.8%	Hard
1122	Relative Sort Array	Go	67.7%	Easy
1123	Lowest Common Ancestor of Deepest Leaves	Go	66.8%	Medium
1124	Longest Well-Performing Interval		32.7%	Medium
1125	Smallest Sufficient Team		46.5%	Hard
1126	Active Businesses		68.5%	Medium
1127	User Purchase Platform		48.9%	Hard
1128	Number of Equivalent Domino Pairs	Go	47.3%	Easy
1129	Shortest Path with Alternating Colors		38.9%	Medium
1130	Minimum Cost Tree From Leaf Values		66.1%	Medium
1131	Maximum of Absolute Value Expression		53.1%	Medium
1132	Reported Posts II		34.4%	Medium
1133	Largest Unique Number		66.9%	Easy
1134	Armstrong Number		78.3%	Easy
1135	Connecting Cities With Minimum Cost		57.5%	Medium
1136	Parallel Courses		61.1%	Hard
1137	N-th Tribonacci Number	Go	55.9%	Easy
1138	Alphabet Board Path		48.4%	Medium
1139	Largest 1-Bordered Square		47.5%	Medium
1140	Stone Game II		63.3%	Medium
1141	User Activity for the Past 30 Days I		54.1%	Easy
1142	User Activity for the Past 30 Days II		34.5%	Easy
1143	Longest Common Subsequence		58.4%	Medium
1144	Decrease Elements To Make Array Zigzag		45.4%	Medium
1145	Binary Tree Coloring Game	Go	51.3%	Medium
1146	Snapshot Array		37.1%	Medium
1147	Longest Chunked Palindrome Decomposition		58.6%	Hard
1148	Article Views I		75.8%	Easy
1149	Article Views II		48.1%	Medium
1150	Check If a Number Is Majority Element in a Sorted Array		59.2%	Easy
1151	Minimum Swaps to Group All 1's Together		59.3%	Medium
1152	Analyze User Website Visit Pattern		43.5%	Medium
1153	String Transforms Into Another String		35.8%	Hard
1154	Day of the Year	Go	49.3%	Easy
1155	Number of Dice Rolls With Target Sum		49.1%	Medium
1156	Swap For Longest Repeated Character Substring		48.9%	Medium
1157	Online Majority Element In Subarray	Go	38.9%	Hard
1158	Market Analysis I		61.7%	Medium
1159	Market Analysis II		52.9%	Hard
1160	Find Words That Can Be Formed by Characters	Go	67.4%	Easy
1161	Maximum Level Sum of a Binary Tree		72.2%	Medium
1162	As Far from Land as Possible		43.4%	Medium
1163	Last Substring in Lexicographical Order		33.8%	Hard
1164	Product Price at a Given Date		65.8%	Medium
1165	Single-Row Keyboard		84.8%	Easy
1166	Design File System		56.8%	Medium
1167	Minimum Cost to Connect Sticks		62.7%	Medium
1168	Optimize Water Distribution in a Village		60.9%	Hard
1169	Invalid Transactions		31.2%	Medium
1170	Compare Strings by Frequency of the Smallest Character	Go	58.6%	Easy
1171	Remove Zero Sum Consecutive Nodes from Linked List	Go	41.4%	Medium
1172	Dinner Plate Stacks		38.2%	Hard
1173	Immediate Food Delivery I		80.4%	Easy
1174	Immediate Food Delivery II		58.4%	Medium
1175	Prime Arrangements	Go	51.0%	Easy
1176	Diet Plan Performance		53.9%	Easy
1177	Can Make Palindrome from Substring		34.6%	Medium
1178	Number of Valid Words for Each Puzzle		37.9%	Hard
1179	Reformat Department Table		80.5%	Easy
1180	Count Substrings with Only One Distinct Letter		77.0%	Easy
1181	Before and After Puzzle		44.4%	Medium
1182	Shortest Distance to Target Color		52.8%	Medium
1183	Maximum Number of Ones		54.4%	Hard
1184	Distance Between Bus Stops	Go	54.4%	Easy
1185	Day of the Week	Go	64.0%	Easy
1186	Maximum Subarray Sum with One Deletion		37.4%	Medium
1187	Make Array Strictly Increasing		41.8%	Hard
1188	Design Bounded Blocking Queue		70.5%	Medium
1189	Maximum Number of Balloons	Go	61.2%	Easy
1190	Reverse Substrings Between Each Pair of Parentheses		61.5%	Medium
1191	K-Concatenation Maximum Sum		25.9%	Medium
1192	Critical Connections in a Network		48.6%	Hard
1193	Monthly Transactions I		68.2%	Medium
1194	Tournament Winners		52.8%	Hard
1195	Fizz Buzz Multithreaded		68.3%	Medium
1196	How Many Apples Can You Put into the Basket		68.1%	Easy
1197	Minimum Knight Moves		36.1%	Medium
1198	Find Smallest Common Element in All Rows		74.9%	Medium
1199	Minimum Time to Build Blocks		37.3%	Hard
1200	Minimum Absolute Difference	Go	66.6%	Easy
1201	Ugly Number III	Go	25.9%	Medium
1202	Smallest String With Swaps	Go	46.5%	Medium
1203	Sort Items by Groups Respecting Dependencies		47.6%	Hard
1204	Last Person to Fit in the Elevator		69.7%	Medium
1205	Monthly Transactions II		45.1%	Medium
1206	Design Skiplist		57.4%	Hard
1207	Unique Number of Occurrences	Go	71.6%	Easy
1208	Get Equal Substrings Within Budget	Go	41.9%	Medium
1209	Remove All Adjacent Duplicates in String II		56.8%	Medium
1210	Minimum Moves to Reach Target with Rotations		45.2%	Hard
1211	Queries Quality and Percentage		68.3%	Easy
1212	Team Scores in Football Tournament		55.7%	Medium
1213	Intersection of Three Sorted Arrays		78.9%	Easy
1214	Two Sum BSTs		67.6%	Medium
1215	Stepping Numbers		41.6%	Medium
1216	Valid Palindrome III		47.7%	Hard
1217	Play with Chips	Go	64.3%	Easy
1218	Longest Arithmetic Subsequence of Given Difference		44.5%	Medium
1219	Path with Maximum Gold		65.1%	Medium
1220	Count Vowels Permutation		53.9%	Hard
1221	Split a String in Balanced Strings	Go	83.2%	Easy
1222	Queens That Can Attack the King		68.7%	Medium
1223	Dice Roll Simulation		45.6%	Medium
1224	Maximum Equal Frequency		33.5%	Hard
1225	Report Contiguous Dates		61.2%	Hard
1226	The Dining Philosophers		55.7%	Medium
1227	Airplane Seat Assignment Probability		61.0%	Medium
1228	Missing Number In Arithmetic Progression		52.6%	Easy
1229	Meeting Scheduler		52.6%	Medium
1230	Toss Strange Coins		48.7%	Medium
1231	Divide Chocolate		52.3%	Hard
1232	Check If It Is a Straight Line	Go	45.3%	Easy
1233	Remove Sub-Folders from the Filesystem		59.5%	Medium
1234	Replace the Substring for Balanced String	Go	33.3%	Medium
1235	Maximum Profit in Job Scheduling	Go	44.1%	Hard
1236	Web Crawler		64.3%	Medium
1237	Find Positive Integer Solution for a Given Equation		69.6%	Easy
1238	Circular Permutation in Binary Representation		64.9%	Medium
1239	Maximum Length of a Concatenated String with Unique Characters		47.8%	Medium
1240	Tiling a Rectangle with the Fewest Squares		50.1%	Hard
1241	Number of Comments per Post		67.0%	Easy
1242	Web Crawler Multithreaded		45.9%	Medium
1243	Array Transformation		51.0%	Easy
1244	Design A Leaderboard		60.7%	Medium
1245	Tree Diameter		60.0%	Medium
1246	Palindrome Removal		46.0%	Hard
1247	Minimum Swaps to Make Strings Equal		60.0%	Medium
1248	Count Number of Nice Subarrays		56.4%	Medium
1249	Minimum Remove to Make Valid Parentheses		62.5%	Medium
1250	Check If It Is a Good Array		55.7%	Hard
1251	Average Selling Price		81.4%	Easy
1252	Cells with Odd Values in a Matrix	Go	78.1%	Easy
1253	Reconstruct a 2-Row Binary Matrix		40.4%	Medium
1254	Number of Closed Islands	Go	60.3%	Medium
1255	Maximum Score Words Formed by Letters		69.3%	Hard
1256	Encode Number		66.0%	Medium
1257	Smallest Common Region		58.8%	Medium
1258	Synonymous Sentences		64.4%	Medium
1259	Handshakes That Don't Cross		53.5%	Hard
1260	Shift 2D Grid	Go	61.3%	Easy
1261	Find Elements in a Contaminated Binary Tree		74.3%	Medium
1262	Greatest Sum Divisible by Three		47.6%	Medium
1263	Minimum Moves to Move a Box to Their Target Location		41.4%	Hard
1264	Page Recommendations		67.5%	Medium
1265	Print Immutable Linked List in Reverse		94.6%	Medium
1266	Minimum Time Visiting All Points	Go	79.6%	Easy
1267	Count Servers that Communicate		57.9%	Medium
1268	Search Suggestions System		63.3%	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		87.0%	Medium
1271	Hexspeak		54.2%	Easy
1272	Remove Interval		58.6%	Medium
1273	Delete Tree Nodes		63.5%	Medium
1274	Number of Ships in a Rectangle		66.5%	Hard
1275	Find Winner on a Tic Tac Toe Game	Go	52.9%	Easy
1276	Number of Burgers with No Waste of Ingredients		49.6%	Medium
1277	Count Square Submatrices with All Ones		73.2%	Medium
1278	Palindrome Partitioning III		59.9%	Hard
1279	Traffic Light Controlled Intersection		74.3%	Easy
1280	Students and Examinations		72.1%	Easy
1281	Subtract the Product and Sum of Digits of an Integer	Go	85.2%	Easy
1282	Group the People Given the Group Size They Belong To		83.9%	Medium
1283	Find the Smallest Divisor Given a Threshold	Go	47.6%	Medium
1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix		69.5%	Hard
1285	Find the Start and End Number of Continuous Ranges		83.7%	Medium
1286	Iterator for Combination		68.1%	Medium
1287	Element Appearing More Than 25% In Sorted Array	Go	60.2%	Easy
1288	Remove Covered Intervals		58.0%	Medium
1289	Minimum Falling Path Sum II		61.0%	Hard
1290	Convert Binary Number in a Linked List to Integer	Go	80.2%	Easy
1291	Sequential Digits		53.4%	Medium
1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold		48.5%	Medium
1293	Shortest Path in a Grid with Obstacles Elimination		42.7%	Hard
1294	Weather Type in Each Country		63.1%	Easy
1295	Find Numbers with Even Number of Digits	Go	81.6%	Easy
1296	Divide Array in Sets of K Consecutive Numbers		53.7%	Medium
1297	Maximum Number of Occurrences of a Substring		47.3%	Medium
1298	Maximum Candies You Can Get from Boxes		58.9%	Hard
1299	Replace Elements with Greatest Element on Right Side	Go	75.4%	Easy
1300	Sum of Mutated Array Closest to Target	Go	44.2%	Medium
1301	Number of Paths with Max Score		37.2%	Hard
1302	Deepest Leaves Sum	Go	83.6%	Medium
1303	Find the Team Size		87.8%	Easy
1304	Find N Unique Integers Sum up to Zero	Go	76.3%	Easy
1305	All Elements in Two Binary Search Trees	Go	76.1%	Medium
1306	Jump Game III	Go	60.5%	Medium
1307	Verbal Arithmetic Puzzle		37.6%	Hard
1308	Running Total for Different Genders		84.0%	Medium
1309	Decrypt String from Alphabet to Integer Mapping		76.7%	Easy
1310	XOR Queries of a Subarray		68.6%	Medium
1311	Get Watched Videos by Your Friends		43.1%	Medium
1312	Minimum Insertion Steps to Make a String Palindrome		58.1%	Hard
1313	Decompress Run-Length Encoded List	Go	85.1%	Easy
1314	Matrix Block Sum		73.7%	Medium
1315	Sum of Nodes with Even-Valued Grandparent		83.5%	Medium
1316	Distinct Echo Substrings		46.4%	Hard
1317	Convert Integer to the Sum of Two No-Zero Integers	Go	56.7%	Easy
1318	Minimum Flips to Make a OR b Equal to c		62.8%	Medium
1319	Number of Operations to Make Network Connected		53.1%	Medium
1320	Minimum Distance to Type a Word Using Two Fingers		62.3%	Hard
1321	Restaurant Growth		67.7%	Medium
1322	Ads Performance		57.8%	Easy
1323	Maximum 69 Number		77.9%	Easy
1324	Print Words Vertically		58.0%	Medium
1325	Delete Leaves With a Given Value		72.9%	Medium
1326	Minimum Number of Taps to Open to Water a Garden		43.5%	Hard
1327	List the Products Ordered in a Period		76.3%	Easy
1328	Break a Palindrome		43.3%	Medium
1329	Sort the Matrix Diagonally		78.4%	Medium
1330	Reverse Subarray To Maximize Array Value		35.1%	Hard
1331	Rank Transform of an Array		58.1%	Easy
1332	Remove Palindromic Subsequences		60.0%	Easy
1333	Filter Restaurants by Vegan-Friendly, Price and Distance		54.6%	Medium
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance		44.5%	Medium
1335	Minimum Difficulty of a Job Schedule		57.5%	Hard
1336	Number of Transactions per Visit		43.5%	Hard
1337	The K Weakest Rows in a Matrix		68.7%	Easy
1338	Reduce Array Size to The Half		66.6%	Medium
1339	Maximum Product of Splitted Binary Tree		37.2%	Medium
1340	Jump Game V		57.5%	Hard
1341	Movie Rating		56.6%	Medium
1342	Number of Steps to Reduce a Number to Zero		86.3%	Easy
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold		64.2%	Medium
1344	Angle Between Hands of a Clock		61.4%	Medium
1345	Jump Game IV		38.1%	Hard
1346	Check If N and Its Double Exist		38.0%	Easy
1347	Minimum Number of Steps to Make Two Strings Anagram		74.6%	Medium
1348	Tweet Counts Per Frequency		29.0%	Medium
1349	Maximum Students Taking Exam		41.9%	Hard
1350	Students With Invalid Departments		89.4%	Easy
1351	Count Negative Numbers in a Sorted Matrix		76.6%	Easy
1352	Product of the Last K Numbers		43.6%	Medium
1353	Maximum Number of Events That Can Be Attended		30.5%	Medium
1354	Construct Target Array With Multiple Sums		31.9%	Hard
1355	Activity Participants		69.2%	Medium
1356	Sort Integers by The Number of 1 Bits		68.6%	Easy
1357	Apply Discount Every n Orders		66.0%	Medium
1358	Number of Substrings Containing All Three Characters		58.0%	Medium
1359	Count All Valid Pickup and Delivery Options		57.9%	Hard
1360	Number of Days Between Two Dates		48.8%	Easy
1361	Validate Binary Tree Nodes		48.6%	Medium
1362	Closest Divisors		56.7%	Medium
1363	Largest Multiple of Three		33.5%	Hard
1364	Number of Trusted Contacts of a Customer		75.3%	Medium
1365	How Many Numbers Are Smaller Than the Current Number		85.6%	Easy
1366	Rank Teams by Votes		52.4%	Medium
1367	Linked List in Binary Tree		39.7%	Medium
1368	Minimum Cost to Make at Least One Valid Path in a Grid		54.4%	Hard
1369	Get the Second Most Recent Activity		64.7%	Hard
1370	Increasing Decreasing String		75.6%	Easy
1371	Find the Longest Substring Containing Vowels in Even Counts		57.3%	Medium
1372	Longest ZigZag Path in a Binary Tree		54.0%	Medium
1373	Maximum Sum BST in Binary Tree		40.2%	Hard
1374	Generate a String With Characters That Have Odd Counts		75.4%	Easy
1375	Bulb Switcher III		62.5%	Medium
1376	Time Needed to Inform All Employees		55.5%	Medium
1377	Frog Position After T Seconds		33.6%	Hard
1378	Replace Employee ID With The Unique Identifier		87.4%	Easy
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree		83.8%	Medium
1380	Lucky Numbers in a Matrix	Go	71.4%	Easy
1381	Design a Stack With Increment Operation		74.7%	Medium
1382	Balance a Binary Search Tree		74.8%	Medium
1383	Maximum Performance of a Team		31.8%	Hard
1384	Total Sales Amount by Year		62.8%	Hard
1385	Find the Distance Value Between Two Arrays	Go	67.1%	Easy
1386	Cinema Seat Allocation		34.8%	Medium
1387	Sort Integers by The Power Value		70.1%	Medium
1388	Pizza With 3n Slices		44.7%	Hard
1389	Create Target Array in the Given Order	Go	84.1%	Easy
1390	Four Divisors		38.1%	Medium
1391	Check if There is a Valid Path in a Grid		44.5%	Medium
1392	Longest Happy Prefix		40.0%	Hard
1393	Capital Gain/Loss		89.2%	Medium
1394	Find Lucky Integer in an Array		64.5%	Easy
1395	Count Number of Teams		81.9%	Medium
1396	Design Underground System		64.7%	Medium
1397	Find All Good Strings		37.2%	Hard
1398	Customers Who Bought Products A and B but Not C		80.6%	Medium
1399	Count Largest Group		65.0%	Easy
1400	Construct K Palindrome Strings		60.4%	Medium
1401	Circle and Rectangle Overlapping		41.8%	Medium
1402	Reducing Dishes		72.8%	Hard
1403	Minimum Subsequence in Non-Increasing Order		70.8%	Easy
1404	Number of Steps to Reduce a Number in Binary Representation to One		50.3%	Medium
1405	Longest Happy String		49.0%	Medium
1406	Stone Game III		56.0%	Hard
1407	Top Travellers		82.1%	Easy
1408	String Matching in an Array		61.4%	Easy
1409	Queries on a Permutation With Key		81.6%	Medium
1410	HTML Entity Parser		53.9%	Medium
1411	Number of Ways to Paint N × 3 Grid		61.2%	Hard
1412	Find the Quiet Students in All Exams		66.6%	Hard
1413	Minimum Value to Get Positive Step by Step Sum		65.2%	Easy
1414	Find the Minimum Number of Fibonacci Numbers Whose Sum Is K		62.4%	Medium
1415	The k-th Lexicographical String of All Happy Strings of Length n		70.4%	Medium
1416	Restore The Array		36.7%	Hard
1417	Reformat The String		55.0%	Easy
1418	Display Table of Food Orders in a Restaurant		65.6%	Medium
1419	Minimum Number of Frogs Croaking		46.3%	Medium
1420	Build Array Where You Can Find The Maximum Exactly K Comparisons		65.2%	Hard
1421	NPV Queries		80.5%	Medium
1422	Maximum Score After Splitting a String		54.7%	Easy
1423	Maximum Points You Can Obtain from Cards		42.5%	Medium
1424	Diagonal Traverse II		42.3%	Medium
1425	Constrained Subsequence Sum		44.1%	Hard
1426	Counting Elements		58.7%	Easy
1427	Perform String Shifts		53.0%	Easy
1428	Leftmost Column with at Least a One		46.8%	Medium
1429	First Unique Number		47.0%	Medium
1430	Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree		44.8%	Medium
1431	Kids With the Greatest Number of Candies		88.9%	Easy
1432	Max Difference You Can Get From Changing an Integer		42.8%	Medium
1433	Check If a String Can Break Another String		65.7%	Medium
1434	Number of Ways to Wear Different Hats to Each Other		38.0%	Hard
1435	Create a Session Bar Chart		76.7%	Easy
1436	Destination City		77.3%	Easy
1437	Check If All 1's Are at Least Length K Places Away		63.3%	Medium
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit		41.9%	Medium
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows		59.4%	Hard
1440	Evaluate Boolean Expression		70.1%	Medium
1441	Build an Array With Stack Operations		68.8%	Easy
1442	Count Triplets That Can Form Two Arrays of Equal XOR		69.4%	Medium
1443	Minimum Time to Collect All Apples in a Tree		55.5%	Medium
1444	Number of Ways of Cutting a Pizza		52.7%	Hard
1445	Apples & Oranges		87.2%	Medium
1446	Consecutive Characters		60.4%	Easy
1447	Simplified Fractions		61.0%	Medium
1448	Count Good Nodes in Binary Tree		70.6%	Medium
1449	Form Largest Integer With Digits That Add up to Target		41.8%	Hard
1450	Number of Students Doing Homework at a Given Time		78.1%	Easy
1451	Rearrange Words in a Sentence		54.8%	Medium
1452	People Whose List of Favorite Companies Is Not a Subset of Another List		53.3%	Medium
1453	Maximum Number of Darts Inside of a Circular Dartboard		33.7%	Hard
1454	Active Users		37.5%	Medium
1455	Check If a Word Occurs As a Prefix of Any Word in a Sentence	Go	64.7%	Easy
1456	Maximum Number of Vowels in a Substring of Given Length		52.4%	Medium
1457	Pseudo-Palindromic Paths in a Binary Tree		67.2%	Medium
1458	Max Dot Product of Two Subsequences		41.7%	Hard
1459	Rectangles Area		61.5%	Medium
1460	Make Two Arrays Equal by Reversing Sub-arrays		74.0%	Easy
1461	Check If a String Contains All Binary Codes of Size K		44.6%	Medium
1462	Course Schedule IV		41.7%	Medium
1463	Cherry Pickup II		65.5%	Hard
1464	Maximum Product of Two Elements in an Array	Go	78.1%	Easy
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts		30.8%	Medium
1466	Reorder Routes to Make All Paths Lead to the City Zero		63.6%	Medium
1467	Probability of a Two Boxes Having The Same Number of Distinct Balls		61.1%	Hard
1468	Calculate Salaries		78.0%	Medium
1469	Find All The Lonely Nodes		81.5%	Easy
1470	Shuffle the Array	Go	89.0%	Easy
1471	The k Strongest Values in an Array		57.0%	Medium
1472	Design Browser History		64.5%	Medium
1473	Paint House III		48.1%	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		75.7%	Easy
1476	Subrectangle Queries		90.5%	Medium
1477	Find Two Non-overlapping Sub-arrays Each With Target Sum		29.8%	Medium
1478	Allocate Mailboxes		55.0%	Hard
1479	Sales by Day of the Week		83.4%	Hard
1480	Running Sum of 1d Array		90.6%	Easy
1481	Least Number of Unique Integers after K Removals		53.7%	Medium
1482	Minimum Number of Days to Make m Bouquets		45.7%	Medium
1483	Kth Ancestor of a Tree Node		27.6%	Hard
1484	Group Sold Products By The Date		86.0%	Easy
1485	Clone Binary Tree With Random Pointer		81.4%	Medium
1486	XOR Operation in an Array		85.1%	Easy
1487	Making File Names Unique		29.2%	Medium
1488	Avoid Flood in The City		25.3%	Medium
1489	Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree		50.5%	Hard
1490	Clone N-ary Tree		84.7%	Medium
1491	Average Salary Excluding the Minimum and Maximum Salary		70.2%	Easy
1492	The kth Factor of n		68.0%	Medium
1493	Longest Subarray of 1's After Deleting One Element		58.4%	Medium
1494	Parallel Courses II		32.2%	Hard
1495	Friendly Movies Streamed Last Month		52.9%	Easy
1496	Path Crossing		55.9%	Easy
1497	Check If Array Pairs Are Divisible by k		41.2%	Medium
1498	Number of Subsequences That Satisfy the Given Sum Condition		36.7%	Medium
1499	Max Value of Equation		44.6%	Hard
1500	Design a File Sharing System		46.4%	Medium
1501	Countries You Can Safely Invest In		63.8%	Medium
1502	Can Make Arithmetic Progression From Sequence		73.4%	Easy
1503	Last Moment Before All Ants Fall Out of a Plank		51.5%	Medium
1504	Count Submatrices With All Ones		61.6%	Medium
1505	Minimum Possible Integer After at Most K Adjacent Swaps On Digits		36.1%	Hard
1506	Find Root of N-Ary Tree		79.8%	Medium
1507	Reformat Date		60.5%	Easy
1508	Range Sum of Sorted Subarray Sums		68.6%	Medium
1509	Minimum Difference Between Largest and Smallest Value in Three Moves		50.9%	Medium
1510	Stone Game IV		50.2%	Hard
1511	Customer Order Frequency		77.0%	Easy
1512	Number of Good Pairs		88.7%	Easy
1513	Number of Substrings With Only 1s		40.4%	Medium
1514	Path with Maximum Probability		36.5%	Medium
1515	Best Position for a Service Centre		35.8%	Hard
1516	Move Sub-Tree of N-Ary Tree		60.2%	Hard
1517	Find Users With Valid E-Mails		71.2%	Easy
1518	Water Bottles		63.1%	Easy
1519	Number of Nodes in the Sub-Tree With the Same Label		35.1%	Medium
1520	Maximum Number of Non-Overlapping Substrings		32.7%	Hard
1521	Find a Value of a Mysterious Function Closest to Target		43.3%	Hard
1522	Diameter of N-Ary Tree		70.0%	Medium
1523	Count Odd Numbers in an Interval Range		55.7%	Easy
1524	Number of Sub-arrays With Odd Sum		36.3%	Medium
1525	Number of Good Ways to Split a String		70.0%	Medium
1526	Minimum Number of Increments on Subarrays to Form a Target Array		57.5%	Hard
1527	Patients With a Condition		88.4%	Easy
1528	Shuffle String		86.1%	Easy
1529	Bulb Switcher IV		70.4%	Medium
1530	Number of Good Leaf Nodes Pairs		53.4%	Medium
1531	String Compression II		28.6%	Hard
1532	The Most Recent Three Orders		75.1%	Medium
1533	Find the Index of the Large Integer		57.7%	Medium
1534	Count Good Triplets		79.4%	Easy
1535	Find the Winner of an Array Game		45.5%	Medium
1536	Minimum Swaps to Arrange a Binary Grid		41.5%	Medium
1537	Get the Maximum Score		35.7%	Hard
1538	Guess the Majority in a Hidden Array		56.9%	Medium
------------	-------------------------------------------------------	-------	----------------	---------------	-------------

---

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

---

二.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

• 线段数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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