README.md

LeetCode by Go

[LeetCode Online Judge] (https://leetcode.com/) 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 by 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!

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	44.30%	Easy
0002	Add Two Numbers	Go	31.30%	Medium
0003	Longest Substring Without Repeating Characters	Go	28.50%	Medium
0004	Median of Two Sorted Arrays		26.60%	Hard
0005	Longest Palindromic Substring		27.50%	Medium
0006	ZigZag Conversion		32.20%	Medium
0007	Reverse Integer	Go	25.40%	Easy
0008	String to Integer (atoi)		14.70%	Medium
0009	Palindrome Number		43.70%	Easy
0010	Regular Expression Matching		25.40%	Hard
0011	Container With Most Water	Go	45.10%	Medium
0012	Integer to Roman		51.30%	Medium
0013	Roman to Integer		52.60%	Easy
0014	Longest Common Prefix		33.70%	Easy
0015	3Sum	Go	24.20%	Medium
0016	3Sum Closest	Go	45.80%	Medium
0017	Letter Combinations of a Phone Number	Go	41.90%	Medium
0018	4Sum	Go	30.80%	Medium
0019	Remove Nth Node From End of List	Go	34.30%	Medium
0020	Valid Parentheses	Go	36.70%	Easy
0021	Merge Two Sorted Lists	Go	47.70%	Easy
0022	Generate Parentheses	Go	55.50%	Medium
0023	Merge k Sorted Lists	Go	34.90%	Hard
0024	Swap Nodes in Pairs	Go	45.10%	Medium
0025	Reverse Nodes in k-Group	Go	36.80%	Hard
0026	Remove Duplicates from Sorted Array	Go	41.00%	Easy
0027	Remove Element	Go	44.80%	Easy
0028	Implement strStr()	Go	32.20%	Easy
0029	Divide Two Integers	Go	16.10%	Medium
0030	Substring with Concatenation of All Words	Go(是否还有更优解)	23.70%	Hard
0031	Next Permutation		30.60%	Medium
0032	Longest Valid Parentheses		25.70%	Hard
0033	Search in Rotated Sorted Array	Go	33.00%	Medium
0034	Find First and Last Position of Element in Sorted Array	Go	33.70%	Medium
0035	Search Insert Position		40.90%	Easy
0036	Valid Sudoku	Go	43.50%	Medium
0037	Sudoku Solver	Go	37.40%	Hard
0038	Count and Say		40.80%	Easy
0039	Combination Sum	Go	49.10%	Medium
0040	Combination Sum II	Go	42.10%	Medium
0041	First Missing Positive	Go	29.10%	Hard
0042	Trapping Rain Water	Go	43.50%	Hard
0043	Multiply Strings		30.90%	Medium
0044	Wildcard Matching		23.00%	Hard
0045	Jump Game II		28.20%	Hard
0046	Permutations	Go	55.70%	Medium
0047	Permutations II	Go	40.90%	Medium
0048	Rotate Image	Go	49.00%	Medium
0049	Group Anagrams	Go	47.40%	Medium
0050	Pow(x, n)	Go	28.10%	Medium
0051	N-Queens	Go	39.80%	Hard
0052	N-Queens II	Go	52.40%	Hard
0053	Maximum Subarray	Go	43.80%	Easy
0054	Spiral Matrix	Go	30.70%	Medium
0055	Jump Game		32.10%	Medium
0056	Merge Intervals	Go	35.90%	Medium
0057	Insert Interval	Go	31.40%	Hard
0058	Length of Last Word		32.30%	Easy
0059	Spiral Matrix II	Go	47.00%	Medium
0060	Permutation Sequence	Go	33.40%	Medium
0061	Rotate List	Go	27.30%	Medium
0062	Unique Paths	Go	48.00%	Medium
0063	Unique Paths II	Go	33.50%	Medium
0064	Minimum Path Sum	Go	47.30%	Medium
0065	Valid Number		14.10%	Hard
0066	Plus One	Go	41.40%	Easy
0067	Add Binary		39.50%	Easy
0068	Text Justification		23.50%	Hard
0069	Sqrt(x)	Go	31.50%	Easy
0070	Climbing Stairs	Go	44.40%	Easy
0071	Simplify Path	Go	29.00%	Medium
0072	Edit Distance		38.20%	Hard
0073	Set Matrix Zeroes		40.10%	Medium
0074	Search a 2D Matrix		35.00%	Medium
0075	Sort Colors	Go	42.40%	Medium
0076	Minimum Window Substring	Go	31.10%	Hard
0077	Combinations	Go	48.20%	Medium
0078	Subsets	Go	53.40%	Medium
0079	Word Search	Go	31.50%	Medium
0080	Remove Duplicates from Sorted Array II	Go	40.60%	Medium
0081	Search in Rotated Sorted Array II		32.70%	Medium
0082	Remove Duplicates from Sorted List II	Go	33.30%	Medium
0083	Remove Duplicates from Sorted List	Go	42.80%	Easy
0084	Largest Rectangle in Histogram	Go	31.40%	Hard
0085	Maximal Rectangle		33.60%	Hard
0086	Partition List	Go	37.60%	Medium
0087	Scramble String		31.70%	Hard
0088	Merge Sorted Array	Go	36.00%	Easy
0089	Gray Code	Go	46.00%	Medium
0090	Subsets II	Go	42.70%	Medium
0091	Decode Ways	Go	22.50%	Medium
0092	Reverse Linked List II	Go	35.20%	Medium
0093	Restore IP Addresses	Go	31.70%	Medium
0094	Binary Tree Inorder Traversal	Go	57.10%	Medium
0095	Unique Binary Search Trees II	Go	36.00%	Medium
0096	Unique Binary Search Trees	Go	46.60%	Medium
0097	Interleaving String		28.20%	Hard
0098	Validate Binary Search Tree	Go	25.90%	Medium
0099	Recover Binary Search Tree	Go	34.90%	Hard
0100	Same Tree	Go	50.20%	Easy
0101	Symmetric Tree	Go	43.70%	Easy
0102	Binary Tree Level Order Traversal	Go	48.90%	Medium
0103	Binary Tree Zigzag Level Order Traversal	Go	42.10%	Medium
0104	Maximum Depth of Binary Tree	Go	60.90%	Easy
0105	Construct Binary Tree from Preorder and Inorder Traversal		41.60%	Medium
0106	Construct Binary Tree from Inorder and Postorder Traversal		39.70%	Medium
0107	Binary Tree Level Order Traversal II	Go	47.20%	Easy
0108	Convert Sorted Array to Binary Search Tree	Go	51.20%	Easy
0109	Convert Sorted List to Binary Search Tree	Go	41.20%	Medium
0110	Balanced Binary Tree	Go	41.20%	Easy
0111	Minimum Depth of Binary Tree	Go	35.40%	Easy
0112	Path Sum	Go	38.00%	Easy
0113	Path Sum II	Go	41.00%	Medium
0114	Flatten Binary Tree to Linked List	Go	42.80%	Medium
0115	Distinct Subsequences		35.20%	Hard
0116	Populating Next Right Pointers in Each Node		38.20%	Medium
0117	Populating Next Right Pointers in Each Node II		34.70%	Medium
0118	Pascal's Triangle		46.50%	Easy
0119	Pascal's Triangle II		44.00%	Easy
0120	Triangle	Go	39.70%	Medium
0121	Best Time to Buy and Sell Stock	Go	47.50%	Easy
0122	Best Time to Buy and Sell Stock II	Go	52.20%	Easy
0123	Best Time to Buy and Sell Stock III		33.90%	Hard
0124	Binary Tree Maximum Path Sum	Go	30.20%	Hard
0125	Valid Palindrome	Go	31.40%	Easy
0126	Word Ladder II	Go	18.00%	Hard
0127	Word Ladder	Go	24.40%	Medium
0128	Longest Consecutive Sequence	Go	41.90%	Hard
0129	Sum Root to Leaf Numbers	Go	42.80%	Medium
0130	Surrounded Regions	Go	23.10%	Medium
0131	Palindrome Partitioning	Go	41.30%	Medium
0132	Palindrome Partitioning II		27.60%	Hard
0133	Clone Graph		27.00%	Medium
0134	Gas Station		34.10%	Medium
0135	Candy		28.60%	Hard
0136	Single Number	Go	60.50%	Easy
0137	Single Number II	Go	46.20%	Medium
0138	Copy List with Random Pointer		27.50%	Medium
0139	Word Break		35.60%	Medium
0140	Word Break II		27.50%	Hard
0141	Linked List Cycle	Go	37.20%	Easy
0142	Linked List Cycle II	Go	32.40%	Medium
0143	Reorder List	Go	31.20%	Medium
0144	Binary Tree Preorder Traversal	Go	51.70%	Medium
0145	Binary Tree Postorder Traversal	Go	48.90%	Hard
0146	LRU Cache		25.90%	Medium
0147	Insertion Sort List	Go	37.60%	Medium
0148	Sort List	Go	35.80%	Medium
0149	Max Points on a Line		15.80%	Hard
0150	Evaluate Reverse Polish Notation	Go	32.50%	Medium
0151	Reverse Words in a String		17.00%	Medium
0152	Maximum Product Subarray	Go	29.40%	Medium
0153	Find Minimum in Rotated Sorted Array		43.10%	Medium
0154	Find Minimum in Rotated Sorted Array II		39.40%	Hard
0155	Min Stack	Go	37.50%	Easy
0156	Binary Tree Upside Down		51.10%	Medium
0157	Read N Characters Given Read4		29.70%	Easy
0158	Read N Characters Given Read4 II - Call multiple times		26.60%	Hard
0159	Longest Substring with At Most Two Distinct Characters		47.20%	Hard
0160	Intersection of Two Linked Lists	Go	34.30%	Easy
0161	One Edit Distance		31.70%	Medium
0162	Find Peak Element		41.40%	Medium
0163	Missing Ranges		23.30%	Medium
0164	Maximum Gap	Go	32.70%	Hard
0165	Compare Version Numbers		23.80%	Medium
0166	Fraction to Recurring Decimal		19.60%	Medium
0167	Two Sum II - Input array is sorted	Go	50.60%	Easy
0168	Excel Sheet Column Title		29.10%	Easy
0169	Majority Element	Go	53.00%	Easy
0170	Two Sum III - Data structure design		30.60%	Easy
0171	Excel Sheet Column Number		51.70%	Easy
0172	Factorial Trailing Zeroes		37.40%	Easy
0173	Binary Search Tree Iterator	Go	49.00%	Medium
0174	Dungeon Game		27.30%	Hard
0175	Combine Two Tables		52.40%	Easy
0176	Second Highest Salary		27.50%	Easy
0177	Nth Highest Salary		26.60%	Medium
0178	Rank Scores		37.10%	Medium
0179	Largest Number	Go	26.00%	Medium
0180	Consecutive Numbers		34.00%	Medium
0181	Employees Earning More Than Their Managers		48.90%	Easy
0182	Duplicate Emails		55.20%	Easy
0183	Customers Who Never Order		45.40%	Easy
0184	Department Highest Salary		29.40%	Medium
0185	Department Top Three Salaries		26.50%	Hard
0186	Reverse Words in a String II		38.10%	Medium
0187	Repeated DNA Sequences	Go	36.30%	Medium
0188	Best Time to Buy and Sell Stock IV		26.40%	Hard
0189	Rotate Array		30.50%	Easy
0190	Reverse Bits	Go	31.70%	Easy
0191	Number of 1 Bits	Go	43.60%	Easy
0192	Word Frequency		26.80%	Medium
0193	Valid Phone Numbers		25.20%	Easy
0194	Transpose File		22.90%	Medium
0195	Tenth Line		33.90%	Easy
0196	Delete Duplicate Emails		33.40%	Easy
0197	Rising Temperature		35.10%	Easy
0198	House Robber	Go	41.10%	Easy
0199	Binary Tree Right Side View	Go	48.30%	Medium
0200	Number of Islands	Go	41.90%	Medium
0201	Bitwise AND of Numbers Range	Go	36.10%	Medium
0202	Happy Number	Go	45.60%	Easy
0203	Remove Linked List Elements	Go	35.90%	Easy
0204	Count Primes	Go	29.20%	Easy
0205	Isomorphic Strings	Go	37.60%	Easy
0206	Reverse Linked List	Go	55.30%	Easy
0207	Course Schedule	Go	38.20%	Medium
0208	Implement Trie (Prefix Tree)	Go	39.00%	Medium
0209	Minimum Size Subarray Sum	Go	35.10%	Medium
0210	Course Schedule II	Go	35.20%	Medium
0211	Add and Search Word - Data structure design	Go	30.70%	Medium
0212	Word Search II	Go	29.00%	Hard
0213	House Robber II	Go	35.40%	Medium
0214	Shortest Palindrome		27.70%	Hard
0215	Kth Largest Element in an Array	Go	48.30%	Medium
0216	Combination Sum III	Go	51.90%	Medium
0217	Contains Duplicate	Go	52.30%	Easy
0218	The Skyline Problem	Go	31.80%	Hard
0219	Contains Duplicate II	Go	35.50%	Easy
0220	Contains Duplicate III	Go	19.80%	Medium
0221	Maximal Square		33.30%	Medium
0222	Count Complete Tree Nodes	Go	34.40%	Medium
0223	Rectangle Area		36.00%	Medium
0224	Basic Calculator	Go	33.00%	Hard
0225	Implement Stack using Queues	Go	39.60%	Easy
0226	Invert Binary Tree	Go	58.50%	Easy
0227	Basic Calculator II		33.70%	Medium
0228	Summary Ranges		36.20%	Medium
0229	Majority Element II	Go	32.30%	Medium
0230	Kth Smallest Element in a BST	Go	51.90%	Medium
0231	Power of Two	Go	42.10%	Easy
0232	Implement Queue using Stacks	Go	43.70%	Easy
0233	Number of Digit One		30.30%	Hard
0234	Palindrome Linked List	Go	36.30%	Easy
0235	Lowest Common Ancestor of a Binary Search Tree	Go	45.10%	Easy
0236	Lowest Common Ancestor of a Binary Tree	Go	37.90%	Medium
0237	Delete Node in a Linked List	Go	54.00%	Easy
0238	Product of Array Except Self		55.40%	Medium
0239	Sliding Window Maximum	Go	38.40%	Hard
0240	Search a 2D Matrix II		41.00%	Medium
0241	Different Ways to Add Parentheses		50.30%	Medium
0242	Valid Anagram	Go	52.50%	Easy
0243	Shortest Word Distance		57.60%	Easy
0244	Shortest Word Distance II		47.60%	Medium
0245	Shortest Word Distance III		53.60%	Medium
0246	Strobogrammatic Number		42.40%	Easy
0247	Strobogrammatic Number II		44.60%	Medium
0248	Strobogrammatic Number III		36.70%	Hard
0249	Group Shifted Strings		49.10%	Medium
0250	Count Univalue Subtrees		49.10%	Medium
0251	Flatten 2D Vector		43.90%	Medium
0252	Meeting Rooms		52.30%	Easy
0253	Meeting Rooms II		43.10%	Medium
0254	Factor Combinations		44.50%	Medium
0255	Verify Preorder Sequence in Binary Search Tree		43.70%	Medium
0256	Paint House		49.10%	Easy
0257	Binary Tree Paths	Go	46.30%	Easy
0258	Add Digits		54.30%	Easy
0259	3Sum Smaller		45.10%	Medium
0260	Single Number III	Go	57.30%	Medium
0261	Graph Valid Tree		40.00%	Medium
0262	Trips and Users		25.40%	Hard
0263	Ugly Number	Go	40.70%	Easy
0264	Ugly Number II		36.60%	Medium
0265	Paint House II		41.70%	Hard
0266	Palindrome Permutation		60.20%	Easy
0267	Palindrome Permutation II		33.90%	Medium
0268	Missing Number	Go	48.60%	Easy
0269	Alien Dictionary		31.30%	Hard
0270	Closest Binary Search Tree Value		44.00%	Easy
0271	Encode and Decode Strings		27.00%	Medium
0272	Closest Binary Search Tree Value II		45.40%	Hard
0273	Integer to English Words		24.50%	Hard
0274	H-Index	Go	34.70%	Medium
0275	H-Index II		35.50%	Medium
0276	Paint Fence		36.60%	Easy
0277	Find the Celebrity		37.10%	Medium
0278	First Bad Version		30.30%	Easy
0279	Perfect Squares		42.30%	Medium
0280	Wiggle Sort		61.20%	Medium
0281	Zigzag Iterator		56.10%	Medium
0282	Expression Add Operators		32.90%	Hard
0283	Move Zeroes	Go	54.50%	Easy
0284	Peeking Iterator		40.90%	Medium
0285	Inorder Successor in BST		35.10%	Medium
0286	Walls and Gates		49.80%	Medium
0287	Find the Duplicate Number	Go	50.00%	Medium
0288	Unique Word Abbreviation		20.10%	Medium
0289	Game of Life		45.90%	Medium
0290	Word Pattern	Go	35.20%	Easy
0291	Word Pattern II		41.10%	Hard
0292	Nim Game		55.70%	Easy
0293	Flip Game		59.00%	Easy
0294	Flip Game II		48.40%	Medium
0295	Find Median from Data Stream		37.10%	Hard
0296	Best Meeting Point		55.00%	Hard
0297	Serialize and Deserialize Binary Tree		41.30%	Hard
0298	Binary Tree Longest Consecutive Sequence		44.20%	Medium
0299	Bulls and Cows		39.70%	Medium
0300	Longest Increasing Subsequence	Go	41.00%	Medium
0301	Remove Invalid Parentheses		39.50%	Hard
0302	Smallest Rectangle Enclosing Black Pixels		49.40%	Hard
0303	Range Sum Query - Immutable	Go	38.40%	Easy
0304	Range Sum Query 2D - Immutable		32.70%	Medium
0305	Number of Islands II		41.70%	Hard
0306	Additive Number	Go	28.40%	Medium
0307	Range Sum Query - Mutable	Go	29.00%	Medium
0308	Range Sum Query 2D - Mutable		32.20%	Hard
0309	Best Time to Buy and Sell Stock with Cooldown	Go	44.20%	Medium
0310	Minimum Height Trees		30.30%	Medium
0311	Sparse Matrix Multiplication		56.70%	Medium
0312	Burst Balloons		47.50%	Hard
0313	Super Ugly Number		41.70%	Medium
0314	Binary Tree Vertical Order Traversal		41.20%	Medium
0315	Count of Smaller Numbers After Self	Go	38.40%	Hard
0316	Remove Duplicate Letters		32.80%	Hard
0317	Shortest Distance from All Buildings		38.10%	Hard
0318	Maximum Product of Word Lengths	Go	48.70%	Medium
0319	Bulb Switcher		44.00%	Medium
0320	Generalized Abbreviation		48.90%	Medium
0321	Create Maximum Number		25.50%	Hard
0322	Coin Change	Go	30.80%	Medium
0323	Number of Connected Components in an Undirected Graph		52.30%	Medium
0324	Wiggle Sort II	Go	28.10%	Medium
0325	Maximum Size Subarray Sum Equals k		44.80%	Medium
0326	Power of Three	Go	41.70%	Easy
0327	Count of Range Sum	Go	32.90%	Hard
0328	Odd Even Linked List	Go	49.50%	Medium
0329	Longest Increasing Path in a Matrix		40.30%	Hard
0330	Patching Array		33.40%	Hard
0331	Verify Preorder Serialization of a Binary Tree	Go	38.80%	Medium
0332	Reconstruct Itinerary		31.70%	Medium
0333	Largest BST Subtree		33.20%	Medium
0334	Increasing Triplet Subsequence		39.60%	Medium
0335	Self Crossing		27.00%	Hard
0336	Palindrome Pairs		31.10%	Hard
0337	House Robber III		48.30%	Medium
0338	Counting Bits	Go	64.90%	Medium
0339	Nested List Weight Sum		68.50%	Easy
0340	Longest Substring with At Most K Distinct Characters		40.00%	Hard
0341	Flatten Nested List Iterator		48.20%	Medium
0342	Power of Four	Go	40.40%	Easy
0343	Integer Break	Go	48.00%	Medium
0344	Reverse String	Go	63.50%	Easy
0345	Reverse Vowels of a String	Go	41.70%	Easy
0346	Moving Average from Data Stream		66.50%	Easy
0347	Top K Frequent Elements	Go	55.30%	Medium
0348	Design Tic-Tac-Toe		50.00%	Medium
0349	Intersection of Two Arrays	Go	55.10%	Easy
0350	Intersection of Two Arrays II	Go	48.10%	Easy
0351	Android Unlock Patterns		46.00%	Medium
0352	Data Stream as Disjoint Intervals		43.70%	Hard
0353	Design Snake Game		30.80%	Medium
0354	Russian Doll Envelopes		34.10%	Hard
0355	Design Twitter		27.50%	Medium
0356	Line Reflection		30.90%	Medium
0357	Count Numbers with Unique Digits	Go	47.10%	Medium
0358	Rearrange String k Distance Apart		32.90%	Hard
0359	Logger Rate Limiter		65.40%	Easy
0360	Sort Transformed Array		46.90%	Medium
0361	Bomb Enemy		43.60%	Medium
0362	Design Hit Counter		59.20%	Medium
0363	Max Sum of Rectangle No Larger Than K		35.30%	Hard
0364	Nested List Weight Sum II		58.00%	Medium
0365	Water and Jug Problem		29.00%	Medium
0366	Find Leaves of Binary Tree		66.00%	Medium
0367	Valid Perfect Square		40.00%	Easy
0368	Largest Divisible Subset		34.90%	Medium
0369	Plus One Linked List		56.40%	Medium
0370	Range Addition		60.60%	Medium
0371	Sum of Two Integers	Go	50.90%	Easy
0372	Super Pow	Go	35.70%	Medium
0373	Find K Pairs with Smallest Sums		34.00%	Medium
0374	Guess Number Higher or Lower		39.60%	Easy
0375	Guess Number Higher or Lower II		37.80%	Medium
0376	Wiggle Subsequence		37.60%	Medium
0377	Combination Sum IV		43.70%	Medium
0378	Kth Smallest Element in a Sorted Matrix		49.70%	Medium
0379	Design Phone Directory		41.70%	Medium
0380	Insert Delete GetRandom O(1)		43.00%	Medium
0381	Insert Delete GetRandom O(1) - Duplicates allowed		32.10%	Hard
0382	Linked List Random Node		49.40%	Medium
0383	Ransom Note		50.10%	Easy
0384	Shuffle an Array		50.30%	Medium
0385	Mini Parser	Go	31.90%	Medium
0386	Lexicographical Numbers		46.50%	Medium
0387	First Unique Character in a String	Go	50.20%	Easy
0388	Longest Absolute File Path		39.30%	Medium
0389	Find the Difference	Go	53.20%	Easy
0390	Elimination Game		43.40%	Medium
0391	Perfect Rectangle		28.30%	Hard
0392	Is Subsequence	Go	46.90%	Medium
0393	UTF-8 Validation	Go	36.00%	Medium
0394	Decode String	Go	45.20%	Medium
0395	Longest Substring with At Least K Repeating Characters		38.80%	Medium
0396	Rotate Function		35.20%	Medium
0397	Integer Replacement	Go	31.50%	Medium
0398	Random Pick Index		50.20%	Medium
0399	Evaluate Division	Go	47.80%	Medium
0400	Nth Digit		30.40%	Easy
0401	Binary Watch	Go	45.40%	Easy
0402	Remove K Digits	Go	26.70%	Medium
0403	Frog Jump		36.40%	Hard
0404	Sum of Left Leaves	Go	49.20%	Easy
0405	Convert a Number to Hexadecimal	Go	42.00%	Easy
0406	Queue Reconstruction by Height		60.10%	Medium
0407	Trapping Rain Water II		39.40%	Hard
0408	Valid Word Abbreviation		29.60%	Easy
0409	Longest Palindrome	Go	48.20%	Easy
0410	Split Array Largest Sum		42.60%	Hard
0411	Minimum Unique Word Abbreviation		35.10%	Hard
0412	Fizz Buzz	Go	59.70%	Easy
0413	Arithmetic Slices		56.00%	Medium
0414	Third Maximum Number
Go	29.10%	Easy
0415	Add Strings		43.90%	Easy
0416	Partition Equal Subset Sum	Go	40.90%	Medium
0417	Pacific Atlantic Water Flow		37.60%	Medium
0418	Sentence Screen Fitting		31.20%	Medium
0419	Battleships in a Board		65.90%	Medium
0420	Strong Password Checker		17.20%	Hard
0421	Maximum XOR of Two Numbers in an Array	Go	51.20%	Medium
0422	Valid Word Square		36.60%	Easy
0423	Reconstruct Original Digits from English		45.70%	Medium
0424	Longest Repeating Character Replacement	Go	44.30%	Medium
0425	Word Squares		44.50%	Hard
0426	Convert Binary Search Tree to Sorted Doubly Linked List		52.50%	Medium
0427	Construct Quad Tree		57.20%	Medium
0428	Serialize and Deserialize N-ary Tree		54.20%	Hard
0429	N-ary Tree Level Order Traversal		59.80%	Easy
0430	Flatten a Multilevel Doubly Linked List		42.60%	Medium
0431	Encode N-ary Tree to Binary Tree		64.20%	Hard
0432	All O`one Data Structure		29.70%	Hard
0433	Minimum Genetic Mutation	Go	38.40%	Medium
0434	Number of Segments in a String		37.00%	Easy
0435	Non-overlapping Intervals	Go	41.60%	Medium
0436	Find Right Interval		42.90%	Medium
0437	Path Sum III	Go	43.00%	Easy
0438	Find All Anagrams in a String	Go	37.50%	Easy
0439	Ternary Expression Parser		53.70%	Medium
0440	K-th Smallest in Lexicographical Order		26.60%	Hard
0441	Arranging Coins	Go	38.10%	Easy
0442	Find All Duplicates in an Array		61.30%	Medium
0443	String Compression		37.90%	Easy
0444	Sequence Reconstruction		20.50%	Medium
0445	Add Two Numbers II	Go	50.40%	Medium
0446	Arithmetic Slices II - Subsequence		30.30%	Hard
0447	Number of Boomerangs	Go	50.00%	Easy
0448	Find All Numbers Disappeared in an Array		53.60%	Easy
0449	Serialize and Deserialize BST		47.50%	Medium
0450	Delete Node in a BST		40.20%	Medium
0451	Sort Characters By Frequency	Go	56.40%	Medium
0452	Minimum Number of Arrows to Burst Balloons		46.60%	Medium
0453	Minimum Moves to Equal Array Elements		49.30%	Easy
0454	4Sum II	Go	50.80%	Medium
0455	Assign Cookies	Go	48.50%	Easy
0456	132 Pattern	Go	27.40%	Medium
0457	Circular Array Loop	Go	27.70%	Medium
0458	Poor Pigs		45.50%	Hard
0459	Repeated Substring Pattern		40.00%	Easy
0460	LFU Cache		29.00%	Hard
0461	Hamming Distance	Go	70.40%	Easy
0462	Minimum Moves to Equal Array Elements II		52.50%	Medium
0463	Island Perimeter	Go	61.20%	Easy
0464	Can I Win		27.30%	Medium
0465	Optimal Account Balancing		42.90%	Hard
0466	Count The Repetitions		27.30%	Hard
0467	Unique Substrings in Wraparound String		34.10%	Medium
0468	Validate IP Address		21.40%	Medium
0469	Convex Polygon		35.50%	Medium
0470	Implement Rand10() Using Rand7()	Go	45.10%	Medium
0471	Encode String with Shortest Length		45.20%	Hard
0472	Concatenated Words		35.10%	Hard
0473	Matchsticks to Square		36.00%	Medium
0474	Ones and Zeroes	Go	39.80%	Medium
0475	Heaters		31.90%	Easy
0476	Number Complement	Go	62.50%	Easy
0477	Total Hamming Distance	Go	49.00%	Medium
0478	Generate Random Point in a Circle		36.90%	Medium
0479	Largest Palindrome Product		27.50%	Hard
0480	Sliding Window Median	Go	32.80%	Hard
0481	Magical String		46.30%	Medium
0482	License Key Formatting		41.10%	Easy
0483	Smallest Good Base		34.20%	Hard
0484	Find Permutation		57.80%	Medium
0485	Max Consecutive Ones		55.10%	Easy
0486	Predict the Winner		46.80%	Medium
0487	Max Consecutive Ones II		46.70%	Medium
0488	Zuma Game		39.10%	Hard
0489	Robot Room Cleaner		64.70%	Hard
0490	The Maze		47.60%	Medium
0491	Increasing Subsequences	Go	42.20%	Medium
0492	Construct the Rectangle		48.80%	Easy
0493	Reverse Pairs	Go	23.30%	Hard
0494	Target Sum		45.40%	Medium
0495	Teemo Attacking		52.30%	Medium
0496	Next Greater Element I	Go	59.80%	Easy
0497	Random Point in Non-overlapping Rectangles		35.90%	Medium
0498	Diagonal Traverse	Go	45.40%	Medium
0499	The Maze III		37.40%	Hard
0500	Keyboard Row	Go	62.40%	Easy
0501	Find Mode in Binary Search Tree		39.60%	Easy
0502	IPO		38.00%	Hard
0503	Next Greater Element II	Go	51.30%	Medium
0504	Base 7		45.00%	Easy
0505	The Maze II		44.10%	Medium
0506	Relative Ranks		48.40%	Easy
0507	Perfect Number		34.40%	Easy
0508	Most Frequent Subtree Sum	Go	54.80%	Medium
0509	Fibonacci Number	Go	66.70%	Easy
0510	Inorder Successor in BST II		53.30%	Medium
0511	Game Play Analysis I		74.40%	Easy
0512	Game Play Analysis II		56.80%	Easy
0513	Find Bottom Left Tree Value		58.60%	Medium
0514	Freedom Trail		40.70%	Hard
0515	Find Largest Value in Each Tree Row	Go	58.00%	Medium
0516	Longest Palindromic Subsequence		47.10%	Medium
0517	Super Washing Machines		37.00%	Hard
0518	Coin Change 2		43.10%	Medium
0519	Random Flip Matrix		33.00%	Medium
0520	Detect Capital		52.60%	Easy
0521	Longest Uncommon Subsequence I		56.50%	Easy
0522	Longest Uncommon Subsequence II		32.90%	Medium
0523	Continuous Subarray Sum		24.20%	Medium
0524	Longest Word in Dictionary through Deleting	Go	46.00%	Medium
0525	Contiguous Array		42.80%	Medium
0526	Beautiful Arrangement	Go	54.80%	Medium
0527	Word Abbreviation		50.20%	Hard
0528	Random Pick with Weight		42.80%	Medium
0529	Minesweeper		53.10%	Medium
0530	Minimum Absolute Difference in BST		50.70%	Easy
0531	Lonely Pixel I		57.60%	Medium
0532	K-diff Pairs in an Array	Go	30.00%	Easy
0533	Lonely Pixel II		46.20%	Medium
0534	Game Play Analysis III		64.60%	Medium
0535	Encode and Decode TinyURL		76.90%	Medium
0536	Construct Binary Tree from String		45.20%	Medium
0537	Complex Number Multiplication		65.70%	Medium
0538	Convert BST to Greater Tree		51.30%	Easy
0539	Minimum Time Difference		48.10%	Medium
0540	Single Element in a Sorted Array		57.40%	Medium
0541	Reverse String II	Go	45.70%	Easy
0542	01 Matrix	Go	36.00%	Medium
0543	Diameter of Binary Tree		46.90%	Easy
0544	Output Contest Matches		73.50%	Medium
0545	Boundary of Binary Tree		35.30%	Medium
0546	Remove Boxes		38.50%	Hard
0547	Friend Circles	Go	53.90%	Medium
0548	Split Array with Equal Sum		43.50%	Medium
0549	Binary Tree Longest Consecutive Sequence II		44.50%	Medium
0550	Game Play Analysis IV		42.20%	Medium
0551	Student Attendance Record I		45.30%	Easy
0552	Student Attendance Record II		33.30%	Hard
0553	Optimal Division		55.50%	Medium
0554	Brick Wall		47.80%	Medium
0555	Split Concatenated Strings		40.00%	Medium
0556	Next Greater Element III		30.00%	Medium
0557	Reverse Words in a String III	Go	64.40%	Easy
0558	Quad Tree Intersection		41.10%	Easy
0559	Maximum Depth of N-ary Tree		65.60%	Easy
0560	Subarray Sum Equals K		42.30%	Medium
0561	Array Partition I		69.30%	Easy
0562	Longest Line of Consecutive One in Matrix		43.80%	Medium
0563	Binary Tree Tilt		47.10%	Easy
0564	Find the Closest Palindrome		18.90%	Hard
0565	Array Nesting		52.80%	Medium
0566	Reshape the Matrix	Go	59.00%	Easy
0567	Permutation in String	Go	38.60%	Medium
0568	Maximum Vacation Days		38.30%	Hard
0569	Median Employee Salary		47.60%	Hard
0570	Managers with at Least 5 Direct Reports		62.90%	Medium
0571	Find Median Given Frequency of Numbers		46.80%	Hard
0572	Subtree of Another Tree	Go	41.80%	Easy
0573	Squirrel Simulation		53.80%	Medium
0574	Winning Candidate		36.80%	Medium
0575	Distribute Candies	Go	59.80%	Easy
0576	Out of Boundary Paths		32.30%	Medium
0577	Employee Bonus		59.90%	Easy
0578	Get Highest Answer Rate Question		35.70%	Medium
0579	Find Cumulative Salary of an Employee		34.30%	Hard
0580	Count Student Number in Departments		42.90%	Medium
0581	Shortest Unsorted Continuous Subarray		30.20%	Easy
0582	Kill Process		56.50%	Medium
0583	Delete Operation for Two Strings		45.10%	Medium
0584	Find Customer Referee		67.90%	Easy
0585	Investments in 2016		47.70%	Medium
0586	Customer Placing the Largest Number of Orders		66.90%	Easy
0587	Erect the Fence		34.40%	Hard
0588	Design In-Memory File System		40.00%	Hard
0589	N-ary Tree Preorder Traversal		67.80%	Easy
0590	N-ary Tree Postorder Traversal		67.90%	Easy
0591	Tag Validator		32.90%	Hard
0592	Fraction Addition and Subtraction		47.20%	Medium
0593	Valid Square		40.60%	Medium
0594	Longest Harmonious Subsequence	Go	44.00%	Easy
0595	Big Countries		74.00%	Easy
0596	Classes More Than 5 Students		35.80%	Easy
0597	Friend Requests I: Overall Acceptance Rate		39.80%	Easy
0598	Range Addition II		48.70%	Easy
0599	Minimum Index Sum of Two Lists	Go	48.20%	Easy
0600	Non-negative Integers without Consecutive Ones		32.80%	Hard
0601	Human Traffic of Stadium		36.80%	Hard
0602	Friend Requests II: Who Has the Most Friends		45.40%	Medium
0603	Consecutive Available Seats		58.60%	Easy
0604	Design Compressed String Iterator		34.90%	Easy
0605	Can Place Flowers		31.00%	Easy
0606	Construct String from Binary Tree		51.70%	Easy
0607	Sales Person		57.30%	Easy
0608	Tree Node		59.10%	Medium
0609	Find Duplicate File in System		55.50%	Medium
0610	Triangle Judgement		61.60%	Easy
0611	Valid Triangle Number		45.40%	Medium
0612	Shortest Distance in a Plane		54.00%	Medium
0613	Shortest Distance in a Line		73.20%	Easy
0614	Second Degree Follower		22.60%	Medium
0615	Average Salary: Departments VS Company		38.00%	Hard
0616	Add Bold Tag in String		39.40%	Medium
0617	Merge Two Binary Trees		70.40%	Easy
0618	Students Report By Geography		43.10%	Hard
0619	Biggest Single Number		39.10%	Easy
0620	Not Boring Movies		62.50%	Easy
0621	Task Scheduler		45.70%	Medium
0622	Design Circular Queue		39.70%	Medium
0623	Add One Row to Tree		47.40%	Medium
0624	Maximum Distance in Arrays		37.40%	Easy
0625	Minimum Factorization		32.00%	Medium
0626	Exchange Seats		54.80%	Medium
0627	Swap Salary		69.20%	Easy
0628	Maximum Product of Three Numbers	Go	46.20%	Easy
0629	K Inverse Pairs Array		29.30%	Hard
0630	Course Schedule III		31.90%	Hard
0631	Design Excel Sum Formula		29.30%	Hard
0632	Smallest Range Covering Elements from K Lists	Go	47.90%	Hard
0633	Sum of Square Numbers		32.70%	Easy
0634	Find the Derangement of An Array		37.80%	Medium
0635	Design Log Storage System		54.40%	Medium
0636	Exclusive Time of Functions	Go	48.80%	Medium
0637	Average of Levels in Binary Tree	Go	59.00%	Easy
0638	Shopping Offers		48.90%	Medium
0639	Decode Ways II		25.30%	Hard
0640	Solve the Equation		40.40%	Medium
0641	Design Circular Deque		49.80%	Medium
0642	Design Search Autocomplete System		38.20%	Hard
0643	Maximum Average Subarray I		39.70%	Easy
0644	Maximum Average Subarray II		28.70%	Hard
0645	Set Mismatch	Go	40.80%	Easy
0646	Maximum Length of Pair Chain		49.00%	Medium
0647	Palindromic Substrings		57.20%	Medium
0648	Replace Words	Go	52.20%	Medium
0649	Dota2 Senate		37.80%	Medium
0650	2 Keys Keyboard		46.80%	Medium
0651	4 Keys Keyboard		50.80%	Medium
0652	Find Duplicate Subtrees		45.90%	Medium
0653	Two Sum IV - Input is a BST		52.60%	Easy
0654	Maximum Binary Tree		76.40%	Medium
0655	Print Binary Tree		52.10%	Medium
0656	Coin Path		27.00%	Hard
0657	Robot Return to Origin		71.70%	Easy
0658	Find K Closest Elements		38.20%	Medium
0659	Split Array into Consecutive Subsequences		40.80%	Medium
0660	Remove 9		51.60%	Hard
0661	Image Smoother		49.00%	Easy
0662	Maximum Width of Binary Tree	Go	39.60%	Medium
0663	Equal Tree Partition		38.10%	Medium
0664	Strange Printer		36.90%	Hard
0665	Non-decreasing Array		19.50%	Easy
0666	Path Sum IV		52.50%	Medium
0667	Beautiful Arrangement II		52.10%	Medium
0668	Kth Smallest Number in Multiplication Table		42.20%	Hard
0669	Trim a Binary Search Tree		60.50%	Easy
0670	Maximum Swap		39.80%	Medium
0671	Second Minimum Node In a Binary Tree		43.30%	Easy
0672	Bulb Switcher II		50.10%	Medium
0673	Number of Longest Increasing Subsequence		33.70%	Medium
0674	Longest Continuous Increasing Subsequence		44.40%	Easy
0675	Cut Off Trees for Golf Event		30.80%	Hard
0676	Implement Magic Dictionary	Go	51.70%	Medium
0677	Map Sum Pairs		51.80%	Medium
0678	Valid Parenthesis String		32.90%	Medium
0679	24 Game		43.00%	Hard
0680	Valid Palindrome II		34.30%	Easy
0681	Next Closest Time		42.70%	Medium
0682	Baseball Game	Go	61.20%	Easy
0683	K Empty Slots		34.20%	Hard
0684	Redundant Connection	Go	52.10%	Medium
0685	Redundant Connection II	Go	30.80%	Hard
0686	Repeated String Match		31.50%	Easy
0687	Longest Univalue Path		33.90%	Easy
0688	Knight Probability in Chessboard		44.60%	Medium
0689	Maximum Sum of 3 Non-Overlapping Subarrays		44.20%	Hard
0690	Employee Importance		54.40%	Easy
0691	Stickers to Spell Word		38.50%	Hard
0692	Top K Frequent Words		46.00%	Medium
0693	Binary Number with Alternating Bits	Go	58.00%	Easy
0694	Number of Distinct Islands		51.40%	Medium
0695	Max Area of Island		57.60%	Medium
0696	Count Binary Substrings		53.60%	Easy
0697	Degree of an Array		50.60%	Easy
0698	Partition to K Equal Sum Subsets		42.50%	Medium
0699	Falling Squares	Go	40.10%	Hard
0700	Search in a Binary Search Tree		68.60%	Easy
0701	Insert into a Binary Search Tree		76.10%	Medium
0702	Search in a Sorted Array of Unknown Size		59.30%	Medium
0703	Kth Largest Element in a Stream		46.60%	Easy
0704	Binary Search		48.00%	Easy
0705	Design HashSet	Go	53.90%	Easy
0706	Design HashMap	Go	56.30%	Easy
0707	Design Linked List	Go	21.60%	Easy
0708	Insert into a Cyclic Sorted List		29.20%	Medium
0709	To Lower Case		77.00%	Easy
0710	Random Pick with Blacklist	Go	31.30%	Hard
0711	Number of Distinct Islands II		46.20%	Hard
0712	Minimum ASCII Delete Sum for Two Strings		54.80%	Medium
0713	Subarray Product Less Than K	Go	36.80%	Medium
0714	Best Time to Buy and Sell Stock with Transaction Fee	Go	50.60%	Medium
0715	Range Module	Go	35.70%	Hard
0716	Max Stack		40.20%	Easy
0717	1-bit and 2-bit Characters	Go	49.20%	Easy
0718	Maximum Length of Repeated Subarray		46.30%	Medium
0719	Find K-th Smallest Pair Distance		29.30%	Hard
0720	Longest Word in Dictionary	Go	45.00%	Easy
0721	Accounts Merge	Go	40.80%	Medium
0722	Remove Comments		31.40%	Medium
0723	Candy Crush		63.40%	Medium
0724	Find Pivot Index		41.30%	Easy
0725	Split Linked List in Parts	Go	49.10%	Medium
0726	Number of Atoms	Go	44.90%	Hard
0727	Minimum Window Subsequence		37.50%	Hard
0728	Self Dividing Numbers		70.50%	Easy
0729	My Calendar I	Go	47.60%	Medium
0730	Count Different Palindromic Subsequences		39.20%	Hard
0731	My Calendar II		44.80%	Medium
0732	My Calendar III	Go	55.20%	Hard
0733	Flood Fill	Go	51.10%	Easy
0734	Sentence Similarity		40.80%	Easy
0735	Asteroid Collision	Go	38.60%	Medium
0736	Parse Lisp Expression		44.30%	Hard
0737	Sentence Similarity II		43.60%	Medium
0738	Monotone Increasing Digits		42.00%	Medium
0739	Daily Temperatures	Go	60.10%	Medium
0740	Delete and Earn		46.10%	Medium
0741	Cherry Pickup		30.10%	Hard
0742	Closest Leaf in a Binary Tree		39.40%	Medium
0743	Network Delay Time		42.40%	Medium
0744	Find Smallest Letter Greater Than Target		44.10%	Easy
0745	Prefix and Suffix Search	Go	30.90%	Hard
0746	Min Cost Climbing Stairs	Go	47.50%	Easy
0747	Largest Number At Least Twice of Others		40.70%	Easy
0748	Shortest Completing Word	Go	54.50%	Easy
0749	Contain Virus		41.40%	Hard
0750	Number Of Corner Rectangles		64.80%	Medium
0751	IP to CIDR		59.70%	Easy
0752	Open the Lock		46.30%	Medium
0753	Cracking the Safe		46.60%	Hard
0754	Reach a Number		32.80%	Easy
0755	Pour Water		40.80%	Medium
0756	Pyramid Transition Matrix	Go	51.80%	Medium
0757	Set Intersection Size At Least Two		37.00%	Hard
0758	Bold Words in String		42.70%	Easy
0759	Employee Free Time		61.50%	Hard
0760	Find Anagram Mappings		79.40%	Easy
0761	Special Binary String		52.00%	Hard
0762	Prime Number of Set Bits in Binary Representation	Go	59.60%	Easy
0763	Partition Labels	Go	70.80%	Medium
0764	Largest Plus Sign		43.50%	Medium
0765	Couples Holding Hands	Go	51.70%	Hard
0766	Toeplitz Matrix	Go	61.90%	Easy
0767	Reorganize String	Go	42.70%	Medium
0768	Max Chunks To Make Sorted II		46.10%	Hard
0769	Max Chunks To Make Sorted		51.90%	Medium
0770	Basic Calculator IV		45.70%	Hard
0771	Jewels and Stones	Go	83.20%	Easy
0772	Basic Calculator III		43.40%	Hard
0773	Sliding Puzzle		52.90%	Hard
0774	Minimize Max Distance to Gas Station		42.00%	Hard
0775	Global and Local Inversions		39.10%	Medium
0776	Split BST		52.70%	Medium
0777	Swap Adjacent in LR String		33.40%	Medium
0778	Swim in Rising Water	Go	47.80%	Hard
0779	K-th Symbol in Grammar		37.50%	Medium
0780	Reaching Points		27.60%	Hard
0781	Rabbits in Forest	Go	51.80%	Medium
0782	Transform to Chessboard		39.80%	Hard
0783	Minimum Distance Between BST Nodes		50.60%	Easy
0784	Letter Case Permutation	Go	57.40%	Easy
0785	Is Graph Bipartite?		43.50%	Medium
0786	K-th Smallest Prime Fraction		39.90%	Hard
0787	Cheapest Flights Within K Stops		35.20%	Medium
0788	Rotated Digits		54.40%	Easy
0789	Escape The Ghosts		55.40%	Medium
0790	Domino and Tromino Tiling		36.00%	Medium
0791	Custom Sort String		62.30%	Medium
0792	Number of Matching Subsequences		43.40%	Medium
0793	Preimage Size of Factorial Zeroes Function		39.10%	Hard
0794	Valid Tic-Tac-Toe State		29.80%	Medium
0795	Number of Subarrays with Bounded Maximum		43.40%	Medium
0796	Rotate String		49.10%	Easy
0797	All Paths From Source to Target		70.70%	Medium
0798	Smallest Rotation with Highest Score		40.40%	Hard
0799	Champagne Tower		34.20%	Medium
0800	Similar RGB Color		59.80%	Easy
0801	Minimum Swaps To Make Sequences Increasing		34.90%	Medium
0802	Find Eventual Safe States		44.10%	Medium
0803	Bricks Falling When Hit	Go	28.80%	Hard
0804	Unique Morse Code Words		74.90%	Easy
0805	Split Array With Same Average		24.50%	Hard
0806	Number of Lines To Write String		63.20%	Easy
0807	Max Increase to Keep City Skyline		81.60%	Medium
0808	Soup Servings		37.50%	Medium
0809	Expressive Words		43.70%	Medium
0810	Chalkboard XOR Game		45.10%	Hard
0811	Subdomain Visit Count	Go	65.60%	Easy
0812	Largest Triangle Area		56.30%	Easy
0813	Largest Sum of Averages		45.50%	Medium
0814	Binary Tree Pruning		71.20%	Medium
0815	Bus Routes	Go	40.30%	Hard
0816	Ambiguous Coordinates		44.20%	Medium
0817	Linked List Components	Go	54.80%	Medium
0818	Race Car		35.20%	Hard
0819	Most Common Word	Go	42.20%	Easy
0820	Short Encoding of Words		47.40%	Medium
0821	Shortest Distance to a Character		63.60%	Easy
0822	Card Flipping Game		40.50%	Medium
0823	Binary Trees With Factors		32.60%	Medium
0824	Goat Latin		57.90%	Easy
0825	Friends Of Appropriate Ages		36.50%	Medium
0826	Most Profit Assigning Work	Go	35.90%	Medium
0827	Making A Large Island		43.40%	Hard
0828	Unique Letter String	Go	39.80%	Hard
0829	Consecutive Numbers Sum		33.50%	Hard
0830	Positions of Large Groups		47.90%	Easy
0831	Masking Personal Information		42.20%	Medium
0832	Flipping an Image		72.90%	Easy
0833	Find And Replace in String		46.50%	Medium
0834	Sum of Distances in Tree	Go	39.70%	Hard
0835	Image Overlap		52.90%	Medium
0836	Rectangle Overlap		46.60%	Easy
0837	New 21 Game		31.80%	Medium
0838	Push Dominoes	Go	44.00%	Medium
0839	Similar String Groups	Go	34.70%	Hard
0840	Magic Squares In Grid		35.60%	Easy
0841	Keys and Rooms		60.50%	Medium
0842	Split Array into Fibonacci Sequence	Go	34.90%	Medium
0843	Guess the Word		43.60%	Hard
0844	Backspace String Compare	Go	46.10%	Easy
0845	Longest Mountain in Array	Go	34.40%	Medium
0846	Hand of Straights		49.50%	Medium
0847	Shortest Path Visiting All Nodes		47.10%	Hard
0848	Shifting Letters		41.00%	Medium
0849	Maximize Distance to Closest Person		41.00%	Easy
0850	Rectangle Area II	Go	45.00%	Hard
0851	Loud and Rich		47.80%	Medium
0852	Peak Index in a Mountain Array		69.70%	Easy
0853	Car Fleet	Go	40.00%	Medium
0854	K-Similar Strings		33.80%	Hard
0855	Exam Room		38.60%	Medium
0856	Score of Parentheses	Go	56.50%	Medium
0857	Minimum Cost to Hire K Workers		47.60%	Hard
0858	Mirror Reflection		52.00%	Medium
0859	Buddy Strings		27.60%	Easy
0860	Lemonade Change		50.60%	Easy
0861	Score After Flipping Matrix		69.80%	Medium
0862	Shortest Subarray with Sum at Least K		22.20%	Hard
0863	All Nodes Distance K in Binary Tree		48.00%	Medium
0864	Shortest Path to Get All Keys	Go	36.20%	Hard
0865	Smallest Subtree with all the Deepest Nodes		56.00%	Medium
0866	Prime Palindrome		20.30%	Medium
0867	Transpose Matrix	Go	63.90%	Easy
0868	Binary Gap		59.50%	Easy
0869	Reordered Power of 2		51.10%	Medium
0870	Advantage Shuffle		42.60%	Medium
0871	Minimum Number of Refueling Stops		29.10%	Hard
0872	Leaf-Similar Trees		63.50%	Easy
0873	Length of Longest Fibonacci Subsequence		46.40%	Medium
0874	Walking Robot Simulation		32.30%	Easy
0875	Koko Eating Bananas		46.20%	Medium
0876	Middle of the Linked List	Go	64.40%	Easy
0877	Stone Game		61.50%	Medium
0878	Nth Magical Number		25.60%	Hard
0879	Profitable Schemes		36.80%	Hard
0880	Decoded String at Index	Go	23.00%	Medium
0881	Boats to Save People	Go	44.00%	Medium
0882	Reachable Nodes In Subdivided Graph		38.30%	Hard
0883	Projection Area of 3D Shapes		65.80%	Easy
0884	Uncommon Words from Two Sentences	Go	60.90%	Easy
0885	Spiral Matrix III	Go	64.40%	Medium
0886	Possible Bipartition		40.90%	Medium
0887	Super Egg Drop		24.80%	Hard
0888	Fair Candy Swap		56.80%	Easy
0889	Construct Binary Tree from Preorder and Postorder Traversal		60.30%	Medium
0890	Find and Replace Pattern		71.30%	Medium
0891	Sum of Subsequence Widths	Go	29.10%	Hard
0892	Surface Area of 3D Shapes		56.10%	Easy
0893	Groups of Special-Equivalent Strings		62.80%	Easy
0894	All Possible Full Binary Trees		71.00%	Medium
0895	Maximum Frequency Stack	Go	56.40%	Hard
0896	Monotonic Array		55.40%	Easy
0897	Increasing Order Search Tree		64.90%	Easy
0898	Bitwise ORs of Subarrays	Go	34.40%	Medium
0899	Orderly Queue		47.50%	Hard
0900	RLE Iterator		50.30%	Medium
0901	Online Stock Span	Go	49.40%	Medium
0902	Numbers At Most N Given Digit Set		28.70%	Hard
0903	Valid Permutations for DI Sequence		44.70%	Hard
0904	Fruit Into Baskets	Go	41.60%	Medium
0905	Sort Array By Parity		72.60%	Easy
0906	Super Palindromes		30.40%	Hard
0907	Sum of Subarray Minimums	Go	27.60%	Medium
0908	Smallest Range I		64.60%	Easy
0909	Snakes and Ladders		33.80%	Medium
0910	Smallest Range II		23.70%	Medium
0911	Online Election		47.10%	Medium
0912	Sort an Array		63.60%	Medium
0913	Cat and Mouse		28.80%	Hard
0914	X of a Kind in a Deck of Cards		34.10%	Easy
0915	Partition Array into Disjoint Intervals		43.50%	Medium
0916	Word Subsets		45.40%	Medium
0917	Reverse Only Letters		55.90%	Easy
0918	Maximum Sum Circular Subarray	Go	32.00%	Medium
0919	Complete Binary Tree Inserter		55.20%	Medium
0920	Number of Music Playlists	Go	43.90%	Hard
0921	Minimum Add to Make Parentheses Valid	Go	70.30%	Medium
0922	Sort Array By Parity II	Go	67.10%	Easy
0923	3Sum With Multiplicity	Go	33.90%	Medium
0924	Minimize Malware Spread	Go	40.10%	Hard
0925	Long Pressed Name	Go	44.50%	Easy
0926	Flip String to Monotone Increasing		49.80%	Medium
0927	Three Equal Parts		30.40%	Hard
0928	Minimize Malware Spread II	Go	39.50%	Hard
0929	Unique Email Addresses		70.50%	Easy
0930	Binary Subarrays With Sum	Go	38.20%	Medium
0931	Minimum Falling Path Sum		59.00%	Medium
0932	Beautiful Array		53.60%	Medium
0933	Number of Recent Calls		69.40%	Easy
0934	Shortest Bridge		44.20%	Medium
0935	Knight Dialer		41.10%	Medium
0936	Stamping The Sequence		36.20%	Hard
0937	Reorder Log Files		56.90%	Easy
0938	Range Sum of BST		78.80%	Easy
0939	Minimum Area Rectangle		50.50%	Medium
0940	Distinct Subsequences II		39.80%	Hard
0941	Valid Mountain Array		35.50%	Easy
0942	DI String Match	Go	70.00%	Easy
0943	Find the Shortest Superstring		38.30%	Hard
0944	Delete Columns to Make Sorted		69.40%	Easy
0945	Minimum Increment to Make Array Unique		42.90%	Medium
0946	Validate Stack Sequences	Go	57.60%	Medium
0947	Most Stones Removed with Same Row or Column	Go	54.20%	Medium
0948	Bag of Tokens		39.30%	Medium
0949	Largest Time for Given Digits		34.20%	Easy
0950	Reveal Cards In Increasing Order		72.20%	Medium
0951	Flip Equivalent Binary Trees		65.20%	Medium
0952	Largest Component Size by Common Factor	Go	26.60%	Hard
0953	Verifying an Alien Dictionary	Go	55.60%	Easy
0954	Array of Doubled Pairs		34.40%	Medium
0955	Delete Columns to Make Sorted II		31.60%	Medium
0956	Tallest Billboard		38.40%	Hard
0957	Prison Cells After N Days		38.20%	Medium
0958	Check Completeness of a Binary Tree		47.60%	Medium
0959	Regions Cut By Slashes	Go	62.50%	Medium
0960	Delete Columns to Make Sorted III		52.80%	Hard
0961	N-Repeated Element in Size 2N Array	Go	72.40%	Easy
0962	Maximum Width Ramp		41.80%	Medium
0963	Minimum Area Rectangle II		44.50%	Medium
0964	Least Operators to Express Number		40.90%	Hard
0965	Univalued Binary Tree		66.90%	Easy
0966	Vowel Spellchecker		41.90%	Medium
0967	Numbers With Same Consecutive Differences		37.10%	Medium
0968	Binary Tree Cameras		35.40%	Hard
0969	Pancake Sorting	Go	62.40%	Medium
0970	Powerful Integers	Go	39.30%	Easy
0971	Flip Binary Tree To Match Preorder Traversal		43.00%	Medium
0972	Equal Rational Numbers		40.20%	Hard
0973	K Closest Points to Origin	Go	62.20%	Medium
0974	Subarray Sums Divisible by K		45.20%	Medium
0975	Odd Even Jump		47.20%	Hard
0976	Largest Perimeter Triangle	Go	57.20%	Easy
0977	Squares of a Sorted Array	Go	72.00%	Easy
0978	Longest Turbulent Subarray	Go	45.60%	Medium
0979	Distribute Coins in Binary Tree		67.20%	Medium
0980	Unique Paths III	Go	71.20%	Hard
0981	Time Based Key-Value Store		50.80%	Medium
0982	Triples with Bitwise AND Equal To Zero		54.00%	Hard
0983	Minimum Cost For Tickets		57.30%	Medium
0984	String Without AAA or BBB	Go	33.90%	Medium
0985	Sum of Even Numbers After Queries		63.40%	Easy
0986	Interval List Intersections	Go	63.30%	Medium
0987	Vertical Order Traversal of a Binary Tree		31.80%	Medium
0988	Smallest String Starting From Leaf		46.00%	Medium
0989	Add to Array-Form of Integer		44.70%	Easy
0990	Satisfiability of Equality Equations	Go	40.10%	Medium
0991	Broken Calculator		40.40%	Medium
0992	Subarrays with K Different Integers	Go	45.20%	Hard
0993	Cousins in Binary Tree	Go	52.40%	Easy
0994	Rotting Oranges		46.40%	Easy
0995	Minimum Number of K Consecutive Bit Flips	Go	48.40%	Hard
0996	Number of Squareful Arrays	Go	47.80%	Hard
0997	Find the Town Judge		49.10%	Easy
0998	Maximum Binary Tree II		61.60%	Medium
0999	Available Captures for Rook		66.10%	Easy
1000	Minimum Cost to Merge Stones		32.10%	Hard
1001	Grid Illumination		34.40%	Hard
1002	Find Common Characters	Go	65.80%	Easy
1003	Check If Word Is Valid After Substitutions	Go	51.80%	Medium
1004	Max Consecutive Ones III	Go	53.40%	Medium
1005	Maximize Sum Of Array After K Negations	Go	49.70%	Easy
1006	Clumsy Factorial		53.70%	Medium
1007	Minimum Domino Rotations For Equal Row		47.90%	Medium
1008	Construct Binary Search Tree from Preorder Traversal		73.10%	Medium
1009	Complement of Base 10 Integer		58.90%	Easy
1010	Pairs of Songs With Total Durations Divisible by 60		45.60%	Easy
1011	Capacity To Ship Packages Within D Days		53.30%	Medium
1012	Numbers With Repeated Digits		34.80%	Hard
1013	Partition Array Into Three Parts With Equal Sum		55.50%	Easy
1014	Best Sightseeing Pair		49.30%	Medium
1015	Smallest Integer Divisible by K		28.40%	Medium
1016	Binary String With Substrings Representing 1 To N		60.70%	Medium
1017	Convert to Base -2	Go	56.70%	Medium
1018	Binary Prefix Divisible By 5		46.60%	Easy
1019	Next Greater Node In Linked List	Go	56.50%	Medium
1020	Number of Enclaves		54.70%	Medium
1021	Remove Outermost Parentheses	Go	75.60%	Easy
1022	Sum of Root To Leaf Binary Numbers		55.90%	Easy
1023	Camelcase Matching		56.50%	Medium
1024	Video Stitching		47.20%	Medium
1025	Divisor Game	Go	63.30%	Easy
1026	Maximum Difference Between Node and Ancestor		59.60%	Medium
1027	Longest Arithmetic Sequence		47.90%	Medium
1028	Recover a Tree From Preorder Traversal		70.20%	Hard
1029	Two City Scheduling		53.90%	Easy
1030	Matrix Cells in Distance Order	Go	65.20%	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays		55.30%	Medium
1032	Stream of Characters		41.30%	Hard
1033	Moving Stones Until Consecutive		35.50%	Easy
1034	Coloring A Border		42.50%	Medium
1035	Uncrossed Lines		51.80%	Medium
1036	Escape a Large Maze		36.40%	Hard
1037	Valid Boomerang		37.60%	Easy
1038	Binary Search Tree to Greater Sum Tree		79.70%	Medium
1039	Minimum Score Triangulation of Polygon		41.50%	Medium
1040	Moving Stones Until Consecutive II	Go	46.20%	Medium
1041	Robot Bounded In Circle		43.40%	Easy
1042	Flower Planting With No Adjacent		48.40%	Easy
1043	Partition Array for Maximum Sum		62.40%	Medium
1044	Longest Duplicate Substring		22.80%	Hard
1045	Customers Who Bought All Products		64.10%	Medium
1046	Last Stone Weight		62.40%	Easy
1047	Remove All Adjacent Duplicates In String	Go	63.60%	Easy
1048	Longest String Chain		47.30%	Medium
1049	Last Stone Weight II	Go	39.90%	Medium
1050	Actors and Directors Who Cooperated At Least Three Times		75.40%	Easy
1051	Height Checker		69.40%	Easy
1052	Grumpy Bookstore Owner	Go	52.00%	Medium
1053	Previous Permutation With One Swap		47.10%	Medium
1054	Distant Barcodes	Go	38.60%	Medium
1055	Shortest Way to Form String		58.20%	Medium
1056	Confusing Number		52.10%	Easy
1057	Campus Bikes		58.90%	Medium
1058	Minimize Rounding Error to Meet Target		41.30%	Medium
1059	All Paths from Source Lead to Destination		45.60%	Medium
1060	Missing Element in Sorted Array		54.20%	Medium
1061	Lexicographically Smallest Equivalent String		59.30%	Medium
1062	Longest Repeating Substring		50.80%	Medium
1063	Number of Valid Subarrays		74.30%	Hard
1064	Fixed Point		79.90%	Easy
1065	Index Pairs of a String		59.30%	Easy
1066	Campus Bikes II		43.30%	Medium
1067	Digit Count in Range		34.40%	Hard
1068	Product Sales Analysis I		77.50%	Easy
1069	Product Sales Analysis II		79.90%	Easy
1070	Product Sales Analysis III		42.70%	Medium
1071	Greatest Common Divisor of Strings		53.60%	Easy
1072	Flip Columns For Maximum Number of Equal Rows		56.20%	Medium
1073	Adding Two Negabinary Numbers	Go	31.60%	Medium
1074	Number of Submatrices That Sum to Target	Go	58.50%	Hard
1075	Project Employees I		58.70%	Easy
1076	Project Employees II		52.80%	Easy
1077	Project Employees III		76.90%	Medium
1078	Occurrences After Bigram	Go	67.40%	Easy
1079	Letter Tile Possibilities	Go	76.50%	Medium
1080	Insufficient Nodes in Root to Leaf Paths		41.10%	Medium
1081	Smallest Subsequence of Distinct Characters		42.80%	Medium
1082	Sales Analysis I		74.20%	Easy
1083	Sales Analysis II		55.00%	Easy
1084	Sales Analysis III		57.80%	Easy
1085	Sum of Digits in the Minimum Number		75.30%	Easy
1086	High Five		76.90%	Easy
1087	Brace Expansion		57.50%	Medium
1088	Confusing Number II		34.10%	Hard
1089	Duplicate Zeros		58.80%	Easy
1090	Largest Values From Labels		56.00%	Medium
1091	Shortest Path in Binary Matrix		35.90%	Medium
1092	Shortest Common Supersequence		47.20%	Hard
1093	Statistics from a Large Sample	Go	41.10%	Medium
1094	Car Pooling		57.10%	Medium
1095	Find in Mountain Array		32.50%	Hard
1096	Brace Expansion II		52.00%	Hard
1097	Game Play Analysis V		51.10%	Hard
1098	Unpopular Books		43.20%	Medium
1099	Two Sum Less Than K		62.80%	Easy
1100	Find K-Length Substrings With No Repeated Characters		72.40%	Medium
1101	The Earliest Moment When Everyone Become Friends		62.20%	Medium
1102	Path With Maximum Minimum Value		42.50%	Medium
1103	Distribute Candies to People		62.00%	Easy
1104	Path In Zigzag Labelled Binary Tree		71.10%	Medium
1105	Filling Bookcase Shelves	Go	53.80%	Medium
1106	Parsing A Boolean Expression		59.00%	Hard
1107	New Users Daily Count		46.30%	Medium
1108	Defanging an IP Address		87.50%	Easy
1109	Corporate Flight Bookings		47.30%	Medium
1110	Delete Nodes And Return Forest		61.90%	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings		63.30%	Medium
1112	Highest Grade For Each Student		60.80%	Medium
1113	Reported Posts		68.20%	Easy
1114	Print in Order		59.20%	Easy
1115	Print FooBar Alternately		59.40%	Medium
1116	Print Zero Even Odd		55.40%	Medium
1117	Building H2O		50.40%	Hard
1118	Number of Days in a Month		57.50%	Easy
1119	Remove Vowels from a String		91.10%	Easy
1120	Maximum Average Subtree		60.90%	Medium
1121	Divide Array Into Increasing Sequences		51.20%	Hard
1122	Relative Sort Array		68.50%	Easy
1123	Lowest Common Ancestor of Deepest Leaves		64.60%	Medium
1124	Longest Well-Performing Interval		27.40%	Medium
1125	Smallest Sufficient Team		43.50%	Hard
1126	Active Businesses		70.80%	Medium
1127	User Purchase Platform		64.50%	Hard
1128	Number of Equivalent Domino Pairs		40.30%	Easy
1129	Shortest Path with Alternating Colors		34.20%	Medium
1130	Minimum Cost Tree From Leaf Values		58.80%	Medium
1131	Maximum of Absolute Value Expression		50.30%	Medium
1132	Reported Posts II		35.50%	Medium
1133	Largest Unique Number		70.40%	Easy
1134	Armstrong Number		79.90%	Easy
1135	Connecting Cities With Minimum Cost		49.40%	Medium
1136	Parallel Courses		58.80%	Hard
1137	N-th Tribonacci Number		61.10%	Easy
1138	Alphabet Board Path		42.40%	Medium
1139	Largest 1-Bordered Square		42.80%	Medium
1140	Stone Game II		60.60%	Medium
1141	User Activity for the Past 30 Days I		55.30%	Easy
1142	User Activity for the Past 30 Days II		38.10%	Easy
1143	Longest Common Subsequence		58.80%	Medium
1144	Decrease Elements To Make Array Zigzag		40.50%	Medium
1145	Binary Tree Coloring Game		45.10%	Medium
1146	Snapshot Array		29.80%	Medium
1147	Longest Chunked Palindrome Decomposition		58.40%	Hard
1148	Article Views I		68.30%	Easy
1149	Article Views II		50.10%	Medium
1150	Check If a Number Is Majority Element in a Sorted Array		72.40%	Easy
1151	Minimum Swaps to Group All 1's Together		51.60%	Medium
1152	Analyze User Website Visit Pattern		33.50%	Medium
1153	String Transforms Into Another String		23.60%	Hard
1154	Day of the Year		52.10%	Easy
1155	Number of Dice Rolls With Target Sum		48.60%	Medium
1156	Swap For Longest Repeated Character Substring		41.10%	Medium
1157	Online Majority Element In Subarray	Go	20.50%	Hard
1158	Market Analysis I		50.5%	Medium
1159	Market Analysis II		46.8%	Hard
1160	Find Words That Can Be Formed by Characters		67.6%	Easy
1161	Maximum Level Sum of a Binary Tree		71.4%	Medium
1162	As Far from Land as Possible		39.5%	Medium
1163	Last Substring in Lexicographical Order		30.2%	Hard
1164	Product Price at a Given Date		59.1%	Medium
1165	Single-Row Keyboard		84.9%	Easy
1166	Design File System		60.0%	Medium
1167	Minimum Cost to Connect Sticks		60.1%	Medium
1168	Optimize Water Distribution in a Village		52.6%	Hard
1169	Invalid Transactions		27.4%	Medium
1170	Compare Strings by Frequency of the Smallest Character		60.5%	Easy
1171	Remove Zero Sum Consecutive Nodes from Linked List		42.3%	Medium
1172	Dinner Plate Stacks		41.6%	Hard
1173	Immediate Food Delivery I		72.5%	Easy
1174	Immediate Food Delivery II		52.3%	Medium
1175	Prime Arrangements		50.3%	Easy
1176	Diet Plan Performance		48.6%	Easy
1177	Can Make Palindrome from Substring		32.0%	Medium
1178	Number of Valid Words for Each Puzzle		34.7%	Hard
1179	Reformat Department Table		67.1%	Easy
1180	Count Substrings with Only One Distinct Letter		78.3%	Easy
1181	Before and After Puzzle		41.9%	Medium
1182	Shortest Distance to Target Color		50.7%	Medium
1183	Maximum Number of Ones		45.7%	Hard
1184	Distance Between Bus Stops		56.7%	Easy
1185	Day of the Week		65.8%	Easy
1186	Maximum Subarray Sum with One Deletion		33.2%	Medium
1187	Make Array Strictly Increasing		39.6%	Hard
1188	Design Bounded Blocking Queue		65.0%	Medium
1189	Maximum Number of Balloons		62.7%	Easy
1190	Reverse Substrings Between Each Pair of Parentheses		57.8%	Medium
1191	K-Concatenation Maximum Sum		24.0%	Medium
1192	Critical Connections in a Network		45.2%	Hard
1193	Monthly Transactions I		58.8%	Medium
1194	Tournament Winners		52.2%	Hard
1195	Fizz Buzz Multithreaded		67.7%	Medium
1196	How Many Apples Can You Put into the Basket		68.7%	Easy
1197	Minimum Knight Moves		30.1%	Medium
1198	Find Smallest Common Element in All Rows		71.8%	Medium
1199	Minimum Time to Build Blocks		30.1%	Hard
1200	Minimum Absolute Difference		66.3%	Easy
1201	Ugly Number III		23.9%	Medium
1202	Smallest String With Swaps		39.2%	Medium
1203	Sort Items by Groups Respecting Dependencies		46.9%	Hard
1204	Last Person to Fit in the Elevator    New		65.8%	Medium
1205	Monthly Transactions II    New		49.3%	Medium
1206	Design Skiplist    New		61.8%	Hard
1207	Unique Number of Occurrences		77.4%	Easy
1208	Get Equal Substrings Within Budget		33.3%	Medium
1209	Remove All Adjacent Duplicates in String II		59.6%	Medium
1210	Minimum Moves to Reach Target with Rotations		40.1%	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：

• 116.Populating Next Right Pointers in Each Node
• 117.Populating Next Right Pointers in Each Node II
• 133.Clone Graph
• 138.Copy List with Random Pointer
• 278.First Bad Version
• 284.Peeking Iterator
• 297.Serialize and Deserialize Binary Tree
• 341.Flatten Nested List Iterator
• 374.Guess Number Higher or Lower
• 449.Serialize and Deserialize BST
• 535.Encode and Decode TinyURL
• 690.Employee Importance

---

二.分类

Array

Title	Solution	Difficulty	Time	Space	收藏
1. Two Sum	Go	Easy	O(n)	O(n)
11. Container With Most Water	Go	Medium	O(n)	O(1)
15. 3Sum	Go	Medium	O(n^2)	O(n)	❤️
16. 3Sum Closest	Go	Medium	O(n^2)	O(1)	❤️
18. 4Sum	Go	Medium	O(n^3)	O(n^2)	❤️
26. Remove Duplicates from Sorted Array	Go	Easy	O(n)	O(1)
27. Remove Element	Go	Easy	O(n)	O(1)
39. Combination Sum	Go	Medium	O(n log n)	O(n)
40. Combination Sum II	Go	Medium	O(n log n)	O(n)
41. First Missing Positive	Go	Hard	O(n)	O(n)
42. Trapping Rain Water	Go	Hard	O(n)	O(1)	❤️
48. Rotate Image	Go	Medium	O(n)	O(1)
53. Maximum Subarray	Go	Easy	O(n)	O(n)
54. Spiral Matrix	Go	Medium	O(n)	O(n^2)
56. Merge Intervals	Go	Medium	O(n log n)	O(1)
57. Insert Interval	Go	Hard	O(n)	O(1)
59. Spiral Matrix II	Go	Medium	O(n)	O(n^2)
62. Unique Paths	Go	Medium	O(n^2)	O(n^2)
63. Unique Paths II	Go	Medium	O(n^2)	O(n^2)
64. Minimum Path Sum	Go	Medium	O(n^2)	O(n^2)
75. Sort Colors	Go	Medium	O(n)	O(1)	❤️
78. Subsets	Go	Medium	O(n^2)	O(n)	❤️
79. Word Search	Go	Medium	O(n^2)	O(n^2)	❤️
80. Remove Duplicates from Sorted Array II	Go	Medium	O(n)	O(1
84. Largest Rectangle in Histogram	Go	Medium	O(n)	O(n)	❤️
88. Merge Sorted Array	Go	Easy	O(n)	O(1)	❤️
90. Subsets II	Go	Medium	O(n^2)	O(n)	❤️
120. Triangle	Go	Medium	O(n^2)	O(n)
121. Best Time to Buy and Sell Stock	Go	Easy	O(n)	O(1)
122. Best Time to Buy and Sell Stock II	Go	Easy	O(n)	O(1)
126. Word Ladder II	Go	Hard	O(n)	O(n^2)	❤️
152. Maximum Product Subarray	Go	Medium	O(n)	O(1)
167. Two Sum II - Input array is sorted	Go	Easy	O(n)	O(1)
209. Minimum Size Subarray Sum	Go	Medium	O(n)	O(1)
216. Combination Sum III	Go	Medium	O(n)	O(1)	❤️
217. Contains Duplicate	Go	Easy	O(n)	O(n)
219. Contains Duplicate II	Go	Easy	O(n)	O(n)
283. Move Zeroes	Go	Easy	O(n)	O(1)
287. Find the Duplicate Number	Go	Easy	O(n)	O(1)	❤️
532. K-diff Pairs in an Array	Go	Easy	O(n)	O(n)
566. Reshape the Matrix	Go	Easy	O(n^2)	O(n^2)
628. Maximum Product of Three Numbers	Go	Easy	O(n)	O(1)
713. Subarray Product Less Than K	Go	Medium	O(n)	O(1)
714. Best Time to Buy and Sell Stock with Transaction Fee	Go	Medium	O(n)	O(1)
746. Min Cost Climbing Stairs	Go	Easy	O(n)	O(1)
766. Toeplitz Matrix	Go	Easy	O(n)	O(1)
867. Transpose Matrix	Go	Easy	O(n)	O(1)
891. Sum of Subsequence Widths	Go	Hard	O(n log n)	O(1)
907. Sum of Subarray Minimums	Go	Medium	O(n)	O(n)	❤️
922. Sort Array By Parity II	Go	Medium	O(n)	O(1)
969. Pancake Sorting	Go	Medium	O(n)	O(1)	❤️
977. Squares of a Sorted Array	Go	Easy	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

String

Title	Solution	Difficulty	Time	Space	收藏
3. Longest Substring Without Repeating Characters	Go	Medium	O(n)	O(1)	❤️
17. Letter Combinations of a Phone Number	Go	Medium	O(log n)	O(1)
20. Valid Parentheses	Go	Easy	O(log n)	O(1)
22. Generate Parentheses	Go	Medium	O(log n)	O(1)
28. Implement strStr()	Go	Easy	O(n)	O(1)
30. Substring with Concatenation of All Words	Go	Hard	O(n)	O(n)	❤️
49. Group Anagrams	Go	Medium	O(n log n)	O(n)
71. Simplify Path	Go	Medium	O(n)	O(n)
76. Minimum Window Substring	Go	Hard	O(n)	O(n)	❤️
91. Decode Ways	Go	Medium	O(n)	O(n)
93. Restore IP Addresses	Go	Medium	O(n)	O(n)	❤️
125. Valid Palindrome	Go	Easy	O(n)	O(1)
126. Word Ladder II	Go	Hard	O(n)	O(n^2)	❤️
344. Reverse String	Go	Easy	O(n)	O(1)
345. Reverse Vowels of a String	Go	Easy	O(n)	O(1)
767. Reorganize String	Go	Medium	O(n log n)	O(log n)	❤️
842. Split Array into Fibonacci Sequence	Go	Medium	O(n^2)	O(1)	❤️
856. Score of Parentheses	Go	Medium	O(n)	O(n)
925. Long Pressed Name	Go	Easy	O(n)	O(1)
1003. Check If Word Is Valid After Substitutions	Go	Medium	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
3. Longest Substring Without Repeating Characters	Go	Medium	O(n)	O(1)	❤️
11. Container With Most Water	Go	Medium	O(n)	O(1)
15. 3Sum	Go	Medium	O(n^2)	O(n)	❤️
16. 3Sum Closest	Go	Medium	O(n^2)	O(1)	❤️
18. 4Sum	Go	Medium	O(n^3)	O(n^2)	❤️
19. Remove Nth Node From End of List	Go	Medium	O(n)	O(1)
26. Remove Duplicates from Sorted Array	Go	Easy	O(n)	O(1)
27. Remove Element	Go	Easy	O(n)	O(1)
28. Implement strStr()	Go	Easy	O(n)	O(1)
30. Substring with Concatenation of All Words	Go	Hard	O(n)	O(n)	❤️
42. Trapping Rain Water	Go	Hard	O(n)	O(1)	❤️
61. Rotate List	Go	Medium	O(n)	O(1)
75. Sort Colors	Go	Medium	O(n)	O(1)	❤️
76. Minimum Window Substring	Go	Hard	O(n)	O(n)	❤️
80. Remove Duplicates from Sorted Array II	Go	Medium	O(n)	O(1
86. Partition List	Go	Medium	O(n)	O(1)	❤️
88. Merge Sorted Array	Go	Easy	O(n)	O(1)	❤️
125. Valid Palindrome	Go	Easy	O(n)	O(1)
141. Linked List Cycle	Go	Easy	O(n)	O(1)	❤️
142. Linked List Cycle II	Go	Medium	O(n)	O(1)	❤️
167. Two Sum II - Input array is sorted	Go	Easy	O(n)	O(1)
209. Minimum Size Subarray Sum	Go	Medium	O(n)	O(1)
234. Palindrome Linked List	Go	Easy	O(n)	O(1)
283. Move Zeroes	Go	Easy	O(n)	O(1)
287. Find the Duplicate Number	Go	Easy	O(n)	O(1)	❤️
344. Reverse String	Go	Easy	O(n)	O(1)
345. Reverse Vowels of a String	Go	Easy	O(n)	O(1)
349. Intersection of Two Arrays	Go	Easy	O(n)	O(n)
350. Intersection of Two Arrays II	Go	Easy	O(n)	O(n)
424. Longest Repeating Character Replacement	Go	Medium	O(n)	O(1)
524. Longest Word in Dictionary through Deleting	Go	Medium	O(n)	O(1)
532. K-diff Pairs in an Array	Go	Easy	O(n)	O(n)
567. Permutation in String	Go	Medium	O(n)	O(1)	❤️
713. Subarray Product Less Than K	Go	Medium	O(n)	O(1)
763. Partition Labels	Go	Medium	O(n)	O(1)	❤️
826. Most Profit Assigning Work	Go	Medium	O(n log n)	O(n)
828. Unique Letter String	Go	Hard	O(n)	O(1)	❤️
838. Push Dominoes	Go	Medium	O(n)	O(n)
844. Backspace String Compare	Go	Easy	O(n)	O(n)
845. Longest Mountain in Array	Go	Medium	O(n)	O(1)
881. Boats to Save People	Go	Medium	O(n log n)	O(1)
904. Fruit Into Baskets	Go	Medium	O(n log n)	O(1)
923. 3Sum With Multiplicity	Go	Medium	O(n^2)	O(n)
925. Long Pressed Name	Go	Easy	O(n)	O(1)
930. Binary Subarrays With Sum	Go	Medium	O(n)	O(n)	❤️
977. Squares of a Sorted Array	Go	Easy	O(n)	O(1)
986. Interval List Intersections	Go	Medium	O(n)	O(1)
992. Subarrays with K Different Integers	Go	Hard	O(n)	O(n)	❤️
1004. Max Consecutive Ones III	Go	Medium	O(n)	O(1)
1093. Statistics from a Large Sample	Go	Medium	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
2. Add Two Numbers	Go	Medium	O(n)	O(1)
19. Remove Nth Node From End of List	Go	Medium	O(n)	O(1)
21. Merge Two Sorted Lists	Go	Easy	O(log n)	O(1)
23. Merge k Sorted Lists	Go	Hard	O(log n)	O(1)	❤️
24. Swap Nodes in Pairs	Go	Medium	O(n)	O(1)
25. Reverse Nodes in k-Group	Go	Hard	O(log n)	O(1)	❤️
61. Rotate List	Go	Medium	O(n)	O(1)
82. Remove Duplicates from Sorted List II	Go	Medium	O(n)	O(1)
83. Remove Duplicates from Sorted List	Go	Easy	O(n)	O(1)
86. Partition List	Go	Medium	O(n)	O(1)	❤️
92. Reverse Linked List II	Go	Medium	O(n)	O(1)	❤️
109. Convert Sorted List to Binary Search Tree	Go	Medium	O(log n)	O(n)
141. Linked List Cycle	Go	Easy	O(n)	O(1)	❤️
142. Linked List Cycle II	Go	Medium	O(n)	O(1)	❤️
143. Reorder List	Go	Medium	O(n)	O(1)	❤️
147. Insertion Sort List	Go	Medium	O(n)	O(1)	❤️
148. Sort List	Go	Medium	O(n log n)	O(n)	❤️
160. Intersection of Two Linked Lists	Go	Easy	O(n)	O(1)	❤️
203. Remove Linked List Elements	Go	Easy	O(n)	O(1)
206. Reverse Linked List	Go	Easy	O(n)	O(1)
234. Palindrome Linked List	Go	Easy	O(n)	O(1)
237. Delete Node in a Linked List	Go	Easy	O(n)	O(1)
328. Odd Even Linked List	Go	Medium	O(n)	O(1)
445. Add Two Numbers II	Go	Medium	O(n)	O(n)
725. Split Linked List in Parts	Go	Medium	O(n)	O(1)
817. Linked List Components	Go	Medium	O(n)	O(1)
707. Design Linked List	Go	Easy	O(n)	O(1)
876. Middle of the Linked List	Go	Easy	O(n)	O(1)	❤️
1019. Next Greater Node In Linked List	Go	Medium	O(n)	O(1)
----------------------------------------------------------------------------	-------------	-------------	-------------	-------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
20. Valid Parentheses	Go	Easy	O(log n)	O(1)
42. Trapping Rain Water	Go	Hard	O(n)	O(1)	❤️
71. Simplify Path	Go	Medium	O(n)	O(n)	❤️
84. Largest Rectangle in Histogram	Go	Medium	O(n)	O(n)	❤️
94. Binary Tree Inorder Traversal	Go	Medium	O(n)	O(1)
103. Binary Tree Zigzag Level Order Traversal	Go	Medium	O(n)	O(n)
144. Binary Tree Preorder Traversal	Go	Medium	O(n)	O(1)
145. Binary Tree Postorder Traversal	Go	Hard	O(n)	O(1)
150. Evaluate Reverse Polish Notation	Go	Medium	O(n)	O(1)
155. Min Stack	Go	Easy	O(n)	O(n)
173. Binary Search Tree Iterator	Go	Medium	O(n)	O(1)
224. Basic Calculator	Go	Hard	O(n)	O(n)
225. Implement Stack using Queues	Go	Easy	O(n)	O(n)
232. Implement Queue using Stacks	Go	Easy	O(n)	O(n)
331. Verify Preorder Serialization of a Binary Tree	Go	Medium	O(n)	O(1)
394. Decode String	Go	Medium	O(n)	O(n)
402. Remove K Digits	Go	Medium	O(n)	O(1)
456. 132 Pattern	Go	Medium	O(n)	O(n)
496. Next Greater Element I	Go	Easy	O(n)	O(n)
503. Next Greater Element II	Go	Medium	O(n)	O(n)
636. Exclusive Time of Functions	Go	Medium	O(n)	O(n)
682. Baseball Game	Go	Easy	O(n)	O(n)
726. Number of Atoms	Go	Hard	O(n)	O(n)	❤️
735. Asteroid Collision	Go	Medium	O(n)	O(n)
739. Daily Temperatures	Go	Medium	O(n)	O(n)
844. Backspace String Compare	Go	Easy	O(n)	O(n)
856. Score of Parentheses	Go	Medium	O(n)	O(n)
880. Decoded String at Index	Go	Medium	O(n)	O(n)
895. Maximum Frequency Stack	Go	Hard	O(n)	O(n)
901. Online Stock Span	Go	Medium	O(n)	O(n)
907. Sum of Subarray Minimums	Go	Medium	O(n)	O(n)	❤️
921. Minimum Add to Make Parentheses Valid	Go	Medium	O(n)	O(n)
946. Validate Stack Sequences	Go	Medium	O(n)	O(n)
1003. Check If Word Is Valid After Substitutions	Go	Medium	O(n)	O(1)
1019. Next Greater Node In Linked List	Go	Medium	O(n)	O(1)
1021. Remove Outermost Parentheses	Go	Medium	O(n)	O(1)
1047. Remove All Adjacent Duplicates In String	Go	Medium	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Tree

Title	Solution	Difficulty	Time	Space	收藏
94. Binary Tree Inorder Traversal	Go	Medium	O(n)	O(1)
96. Unique Binary Search Trees	Go	Medium	O(n^2)	O(n)
98. Validate Binary Search Tree	Go	Medium	O(n)	O(1)
99. Recover Binary Search Tree	Go	Hard	O(n)	O(1)
100. Same Tree	Go	Easy	O(n)	O(1)
101. Symmetric Tree	Go	Easy	O(n)	O(1)
102. Binary Tree Level Order Traversal	Go	Medium	O(n)	O(1)
103. Binary Tree Zigzag Level Order Traversal	Go	Medium	O(n)	O(n)
104. Maximum Depth of Binary Tree	Go	Easy	O(n)	O(1)
107. Binary Tree Level Order Traversal II	Go	Easy	O(n)	O(1)
108. Convert Sorted Array to Binary Search Tree	Go	Easy	O(n)	O(1)
110. Balanced Binary Tree	Go	Easy	O(n)	O(1)
111. Minimum Depth of Binary Tree	Go	Easy	O(n)	O(1)
112. Path Sum	Go	Easy	O(n)	O(1)
113. Path Sum II	Go	Medium	O(n)	O(1)
114. Flatten Binary Tree to Linked List	Go	Medium	O(n)	O(1)
124. Binary Tree Maximum Path Sum	Go	Hard	O(n)	O(1)
129. Sum Root to Leaf Numbers	Go	Medium	O(n)	O(1)
144. Binary Tree Preorder Traversal	Go	Medium	O(n)	O(1)
145. Binary Tree Postorder Traversal	Go	Hard	O(n)	O(1)
173. Binary Search Tree Iterator	Go	Medium	O(n)	O(1)
199. Binary Tree Right Side View	Go	Medium	O(n)	O(1)
222. Count Complete Tree Nodes	Go	Medium	O(n)	O(1)
226. Invert Binary Tree	Go	Easy	O(n)	O(1)
230. Kth Smallest Element in a BST	Go	Medium	O(n)	O(1)
235. Lowest Common Ancestor of a Binary Search Tree	Go	Easy	O(n)	O(1)
236. Lowest Common Ancestor of a Binary Tree	Go	Medium	O(n)	O(1)
257. Binary Tree Paths	Go	Easy	O(n)	O(1)
404. Sum of Left Leaves	Go	Easy	O(n)	O(1)
437. Path Sum III	Go	Easy	O(n)	O(1)
515. Find Largest Value in Each Tree Row	Go	Medium	O(n)	O(n)
637. Average of Levels in Binary Tree	Go	Easy	O(n)	O(n)
993. Cousins in Binary Tree	Go	Easy	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Dynamic Programming

Title	Solution	Difficulty	Time	Space	收藏
53. Maximum Subarray	Go	Easy	O(n)	O(n)
62. Unique Paths	Go	Medium	O(n^2)	O(n^2)
63. Unique Paths II	Go	Medium	O(n^2)	O(n^2)
64. Minimum Path Sum	Go	Medium	O(n^2)	O(n^2)
70. Climbing Stairs	Go	Easy	O(n)	O(n)
91. Decode Ways	Go	Medium	O(n)	O(n)
96. Unique Binary Search Trees	Go	Medium	O(n)	O(n)
120. Triangle	Go	Medium	O(n^2)	O(n)
121. Best Time to Buy and Sell Stock	Go	Easy	O(n)	O(1)
152. Maximum Product Subarray	Go	Medium	O(n)	O(1)
198. House Robber	Go	Easy	O(n)	O(n)
213. House Robber II	Go	Medium	O(n)	O(n)
300. Longest Increasing Subsequence	Go	Medium	O(n log n)	O(n)
309. Best Time to Buy and Sell Stock with Cooldown	Go	Medium	O(n)	O(n)
322. Coin Change	Go	Medium	O(n)	O(n)
338. Counting Bits	Go	Medium	O(n)	O(n)
343. Integer Break	Go	Medium	O(n^2)	O(n)
357. Count Numbers with Unique Digits	Go	Medium	O(1)	O(1)
392. Is Subsequence	Go	Medium	O(n)	O(1)
416. Partition Equal Subset Sum	Go	Medium	O(n^2)	O(n)
714. Best Time to Buy and Sell Stock with Transaction Fee	Go	Medium	O(n)	O(1)
746. Min Cost Climbing Stairs	Go	Easy	O(n)	O(1)
838. Push Dominoes	Go	Medium	O(n)	O(n)
1025. Divisor Game	Go	Easy	O(1)	O(1)
891. Sum of Subsequence Widths	Go	Hard	O(n log n)	O(1)
942. DI String Match	Go	Easy	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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
}

Title	Solution	Difficulty	Time	Space	收藏
17. Letter Combinations of a Phone Number	Go	Medium	O(log n)	O(1)
22. Generate Parentheses	Go	Medium	O(log n)	O(1)
37. Sudoku Solver	Go	Hard	O(n^2)	O(n^2)	❤️
39. Combination Sum	Go	Medium	O(n log n)	O(n)
40. Combination Sum II	Go	Medium	O(n log n)	O(n)
46. Permutations	Go	Medium	O(n)	O(n)	❤️
47. Permutations II	Go	Medium	O(n^2)	O(n)	❤️
51. N-Queens	Go	Hard	O(n^2)	O(n)	❤️
52. N-Queens II	Go	Hard	O(n^2)	O(n)	❤️
60. Permutation Sequence	Go	Medium	O(n log n)	O(1)
77. Combinations	Go	Medium	O(n)	O(n)	❤️
78. Subsets	Go	Medium	O(n^2)	O(n)	❤️
79. Word Search	Go	Medium	O(n^2)	O(n^2)	❤️
89. Gray Codes	Go	Medium	O(n)	O(1)
90. Subsets II	Go	Medium	O(n^2)	O(n)	❤️
93. Restore IP Addresses	Go	Medium	O(n)	O(n)	❤️
126. Word Ladder II	Go	Hard	O(n)	O(n^2)	❤️
131. Palindrome Partitioning	Go	Medium	O(n)	O(n^2)	❤️
211. Add and Search Word - Data structure design	Go	Medium	O(n)	O(n)	❤️
212. Word Search II	Go	Hard	O(n^2)	O(n^2)	❤️
216. Combination Sum III	Go	Medium	O(n)	O(1)	❤️
306. Additive Number	Go	Medium	O(n^2)	O(1)	❤️
357. Count Numbers with Unique Digits	Go	Medium	O(1)	O(1)
401. Binary Watch	Go	Easy	O(1)	O(1)
526. Beautiful Arrangement	Go	Medium	O(n^2)	O(1)	❤️
784. Letter Case Permutation	Go	Easy	O(n)	O(n)
842. Split Array into Fibonacci Sequence	Go	Medium	O(n^2)	O(1)	❤️
980. Unique Paths III	Go	Hard	O(n log n)	O(n)
996. Number of Squareful Arrays	Go	Hard	O(n log n)	O(n)
1079. Letter Tile Possibilities	Go	Medium	O(n^2)	O(1)	❤️
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Depth-first Search

Title	Solution	Difficulty	Time	Space	收藏
98. Validate Binary Search Tree	Go	Medium	O(n)	O(1)
99. Recover Binary Search Tree	Go	Hard	O(n)	O(1)
100. Same Tree	Go	Easy	O(n)	O(1)
101. Symmetric Tree	Go	Easy	O(n)	O(1)
104. Maximum Depth of Binary Tree	Go	Easy	O(n)	O(1)
108. Convert Sorted Array to Binary Search Tree	Go	Easy	O(n)	O(1)
109. Convert Sorted List to Binary Search Tree	Go	Medium	O(log n)	O(n)
110. Balanced Binary Tree	Go	Easy	O(n)	O(1)
111. Minimum Depth of Binary Tree	Go	Easy	O(n)	O(1)
112. Path Sum	Go	Easy	O(n)	O(1)
113. Path Sum II	Go	Medium	O(n)	O(1)
114. Flatten Binary Tree to Linked List	Go	Medium	O(n)	O(1)
124. Binary Tree Maximum Path Sum	Go	Hard	O(n)	O(1)
129. Sum Root to Leaf Numbers	Go	Medium	O(n)	O(1)
199. Binary Tree Right Side View	Go	Medium	O(n)	O(1)
200. Number of Islands	Go	Medium	O(n^2)	O(n^2)
207. Course Schedule	Go	Medium	O(n^2)	O(n^2)
210. Course Schedule II	Go	Medium	O(n^2)	O(n^2)
257. Binary Tree Paths	Go	Easy	O(n)	O(1)
394. Decode String	Go	Medium	O(n)	O(n)
515. Find Largest Value in Each Tree Row	Go	Medium	O(n)	O(n)
542. 01 Matrix	Go	Medium	O(n)	O(1)
980. Unique Paths III	Go	Hard	O(n log n)	O(n)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Breadth-first Search

Title	Solution	Difficulty	Time	Space	收藏
101. Symmetric Tree	Go	Easy	O(n)	O(1)
102. Binary Tree Level Order Traversal	Go	Medium	O(n)	O(1)
103. Binary Tree Zigzag Level Order Traversal	Go	Medium	O(n)	O(n)
107. Binary Tree Level Order Traversal II	Go	Easy	O(n)	O(1)
111. Minimum Depth of Binary Tree	Go	Easy	O(n)	O(1)
126. Word Ladder II	Go	Hard	O(n)	O(n^2)	❤️
127. Word Ladder	Go	Medium	O(n)	O(n)
199. Binary Tree Right Side View	Go	Medium	O(n)	O(1)
200. Number of Islands	Go	Medium	O(n^2)	O(n^2)
207. Course Schedule	Go	Medium	O(n^2)	O(n^2)
210. Course Schedule II	Go	Medium	O(n^2)	O(n^2)
515. Find Largest Value in Each Tree Row	Go	Medium	O(n)	O(n)
542. 01 Matrix	Go	Medium	O(n)	O(1)
993. Cousins in Binary Tree	Go	Easy	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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 1011 题。

Title	Solution	Difficulty	Time	Space	收藏
50. Pow(x, n)	Go	Medium	O(log n)	O(1)
69. Sqrt(x)	Go	Easy	O(log n)	O(1)
167. Two Sum II - Input array is sorted	Go	Easy	O(n)	O(1)
209. Minimum Size Subarray Sum	Go	Medium	O(n)	O(1)
222. Count Complete Tree Nodes	Go	Medium	O(n)	O(1)
230. Kth Smallest Element in a BST	Go	Medium	O(n)	O(1)
287. Find the Duplicate Number	Go	Easy	O(n)	O(1)	❤️
300. Longest Increasing Subsequence	Go	Medium	O(n log n)	O(n)
349. Intersection of Two Arrays	Go	Easy	O(n)	O(n)
350. Intersection of Two Arrays II	Go	Easy	O(n)	O(n)
392. Is Subsequence	Go	Medium	O(n)	O(1)
454. 4Sum II	Go	Medium	O(n^2)	O(n)
710. Random Pick with Blacklist	Go	Hard	O(n)	O(n)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Math

Title	Solution	Difficulty	Time	Space	收藏
2. Add Two Numbers	Go	Medium	O(n)	O(1)
50. Pow(x, n)	Go	Medium	O(log n)	O(1)
60. Permutation Sequence	Go	Medium	O(n log n)	O(1)
69. Sqrt(x)	Go	Easy	O(log n)	O(1)
202. Happy Number	Go	Easy	O(log n)	O(1)
224. Basic Calculator	Go	Hard	O(n)	O(n)
231. Power of Two	Go	Easy	O(1)	O(1)
263. Ugly Number	Go	Easy	O(log n)	O(1)
326. Power of Three	Go	Easy	O(1)	O(1)
343. Integer Break	Go	Medium	O(n^2)	O(n)
357. Count Numbers with Unique Digits	Go	Medium	O(1)	O(1)
628. Maximum Product of Three Numbers	Go	Easy	O(n)	O(1)
885. Spiral Matrix III	Go	Medium	O(n^2)	O(1)
891. Sum of Subsequence Widths	Go	Hard	O(n log n)	O(1)
942. DI String Match	Go	Easy	O(n)	O(1)
976. Largest Perimeter Triangle	Go	Easy	O(n log n)	O(log n)
996. Number of Squareful Arrays	Go	Hard	O(n log n)	O(n)
1025. Divisor Game	Go	Easy	O(1)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Hash Table

Title	Solution	Difficulty	Time	Space	收藏
1. Two Sum	Go	Easy	O(n)	O(n)
3. Longest Substring Without Repeating Characters	Go	Medium	O(n)	O(1)	❤️
18. 4Sum	Go	Medium	O(n^3)	O(n^2)	❤️
30. Substring with Concatenation of All Words	Go	Hard	O(n)	O(n)	❤️
36. Valid Sudoku	Go	Medium	O(n^2)	O(n^2)
37. Sudoku Solver	Go	Hard	O(n^2)	O(n^2)	❤️
49. Group Anagrams	Go	Medium	O(n log n)	O(n)
76. Minimum Window Substring	Go	Hard	O(n)	O(n)	❤️
94. Binary Tree Inorder Traversal	Go	Medium	O(n)	O(1)
138. Copy List with Random Pointer	Go	Medium	O(n)	O(1)
202. Happy Number	Go	Easy	O(log n)	O(1)
205. Isomorphic Strings	Go	Easy	O(log n)	O(n)
217. Contains Duplicate	Go	Easy	O(n)	O(n)
219. Contains Duplicate II	Go	Easy	O(n)	O(n)
242. Valid Anagram	Go	Easy	O(n)	O(n)
274. H-Index	Go	Medium	O(n)	O(n)
290. Word Pattern	Go	Easy	O(n)	O(n)
347. Top K Frequent Elements	Go	Medium	O(n)	O(n)
349. Intersection of Two Arrays	Go	Easy	O(n)	O(n)
350. Intersection of Two Arrays II	Go	Easy	O(n)	O(n)
438. Find All Anagrams in a String	Go	Easy	O(n)	O(1)
447. Number of Boomerangs	Go	Easy	O(n)	O(1)
451. Sort Characters By Frequency	Go	Medium	O(n log n)	O(1)
454. 4Sum II	Go	Medium	O(n^2)	O(n)
648. Replace Words	Go	Medium	O(n)	O(n)
676. Implement Magic Dictionary	Go	Medium	O(n)	O(n)
720. Longest Word in Dictionary	Go	Easy	O(n)	O(n)
726. Number of Atoms	Go	Hard	O(n)	O(n)	❤️
739. Daily Temperatures	Go	Medium	O(n)	O(n)
710. Random Pick with Blacklist	Go	Hard	O(n)	O(n)
895. Maximum Frequency Stack	Go	Hard	O(n)	O(n)
930. Binary Subarrays With Sum	Go	Medium	O(n)	O(n)	❤️
992. Subarrays with K Different Integers	Go	Hard	O(n)	O(n)	❤️
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
56. Merge Intervals	Go	Medium	O(n log n)	O(log n)
57. Insert Interval	Go	Hard	O(n)	O(1)
75. Sort Colors	Go	Medium	O(n)	O(1)	❤️
147. Insertion Sort List	Go	Medium	O(n)	O(1)	❤️
148. Sort List	Go	Medium	O(n log n)	O(log n)	❤️
164. Maximum Gap	Go	Hard	O(n log n)	O(log n)	❤️
179. Largest Number	Go	Medium	O(n log n)	O(log n)	❤️
220. Contains Duplicate III	Go	Medium	O(n log n)	O(1)	❤️
242. Valid Anagram	Go	Easy	O(n)	O(n)
274. H-Index	Go	Medium	O(n)	O(n)
324. Wiggle Sort II	Go	Medium	O(n)	O(n)	❤️
349. Intersection of Two Arrays	Go	Easy	O(n)	O(n)
350. Intersection of Two Arrays II	Go	Easy	O(n)	O(n)
524. Longest Word in Dictionary through Deleting	Go	Medium	O(n)	O(1)
767. Reorganize String	Go	Medium	O(n log n)	O(log n)	❤️
853. Car Fleet	Go	Medium	O(n log n)	O(log n)
710. Random Pick with Blacklist	Go	Hard	O(n)	O(n)
922. Sort Array By Parity II	Go	Easy	O(n)	O(1)
969. Pancake Sorting	Go	Medium	O(n log n)	O(log n)	❤️
973. K Closest Points to Origin	Go	Medium	O(n log n)	O(log n)
976. Largest Perimeter Triangle	Go	Easy	O(n log n)	O(log n)
1030. Matrix Cells in Distance Order	Go	Easy	O(n^2)	O(1)
1054. Distant Barcodes	Go	Medium	O(n log n)	O(log n)	❤️
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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

Title	Solution	Difficulty	Time	Space	收藏
78. Subsets	Go	Medium	O(n^2)	O(n)	❤️
136. Single Number	Go	Easy	O(n)	O(1)
137. Single Number II	Go	Medium	O(n)	O(1)	❤️
169. Majority Element	Go	Easy	O(n)	O(1)	❤️
187. Repeated DNA Sequences	Go	Medium	O(n)	O(1)
190. Reverse Bits	Go	Easy	O(n)	O(1)	❤️
191. Number of 1 Bits	Go	Easy	O(n)	O(1)
201. Bitwise AND of Numbers Range	Go	Medium	O(n)	O(1)	❤️
231. Power of Two	Go	Easy	O(1)	O(1)
260. Single Number III	Go	Medium	O(n)	O(1)	❤️
268. Missing Number	Go	Easy	O(n)	O(1)
318. Maximum Product of Word Lengths	Go	Medium	O(n)	O(1)
338. Counting Bits	Go	Medium	O(n)	O(n)
342. Power of Four	Go	Easy	O(n)	O(1)
371. Sum of Two Integers	Go	Easy	O(n)	O(1)
389. Find the Difference	Go	Easy	O(n)	O(1)
393. UTF-8 Validation	Go	Medium	O(n)	O(1)
397. Integer Replacement	Go	Medium	O(n)	O(1)
401. Binary Watch	Go	Easy	O(1)	O(1)
405. Convert a Number to Hexadecimal	Go	Easy	O(n)	O(1)
421. Maximum XOR of Two Numbers in an Array	Go	Medium	O(n)	O(1)	❤️
461. Hamming Distance	Go	Easy	O(n)	O(1)
476. Number Complement	Go	Easy	O(n)	O(1)
477. Total Hamming Distance	Go	Medium	O(n)	O(1)
693. Binary Number with Alternating Bits	Go	Easy	O(n)	O(1)	❤️
756. Pyramid Transition Matrix	Go	Medium	O(n log n)	O(n)
762. Prime Number of Set Bits in Binary Representation	Go	Easy	O(n)	O(1)
784. Letter Case Permutation	Go	Easy	O(n)	O(1)
898. Bitwise ORs of Subarrays	Go	Medium	O(n)	O(1)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
128. Longest Consecutive Sequence	Go	Hard	O(n)	O(n)	❤️
130. Surrounded Regions	Go	Medium	O(m*n)	O(m*n)
200. Number of Islands	Go	Medium	O(m*n)	O(m*n)
399. Evaluate Division	Go	Medium	O(n)	O(n)
547. Friend Circles	Go	Medium	O(n^2)	O(n)
684. Redundant Connection	Go	Medium	O(n)	O(n)
685. Redundant Connection II	Go	Hard	O(n)	O(n)
721. Accounts Merge	Go	Medium	O(n)	O(n)	❤️
765. Couples Holding Hands	Go	Hard	O(n)	O(n)	❤️
778. Swim in Rising Water	Go	Hard	O(n^2)	O(n)	❤️
803. Bricks Falling When Hit	Go	Hard	O(n^2)	O(n)	❤️
839. Similar String Groups	Go	Hard	O(n^2)	O(n)
924. Minimize Malware Spread	Go	Hard	O(m*n)	O(n)
928. Minimize Malware Spread II	Go	Hard	O(m*n)	O(n)	❤️
947. Most Stones Removed with Same Row or Column	Go	Medium	O(n)	O(n)
952. Largest Component Size by Common Factor	Go	Hard	O(n)	O(n)	❤️
959. Regions Cut By Slashes	Go	Medium	O(n^2)	O(n^2)	❤️
990. Satisfiability of Equality Equations	Go	Medium	O(n)	O(n)
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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。

Title	Solution	Difficulty	Time	Space	收藏
3. Longest Substring Without Repeating Characters	Go	Medium	O(n)	O(1)	❤️
76. Minimum Window Substring	Go	Hard	O(n)	O(n)	❤️
239. Sliding Window Maximum	Go	Hard	O(n * k)	O(n)	❤️
424. Longest Repeating Character Replacement	Go	Medium	O(n)	O(1)
480. Sliding Window Median	Go	Hard	O(n * log k)	O(k)	❤️
567. Permutation in String	Go	Medium	O(n)	O(1)	❤️
978. Longest Turbulent Subarray	Go	Medium	O(n)	O(1)	❤️
992. Subarrays with K Different Integers	Go	Hard	O(n)	O(n)	❤️
995. Minimum Number of K Consecutive Bit Flips	Go	Hard	O(n)	O(1)	❤️
1004. Max Consecutive Ones III	Go	Medium	O(n)	O(1)
1040. Moving Stones Until Consecutive II	Go	Medium	O(n log n)	O(1)	❤️
1052. Grumpy Bookstore Owner	Go	Medium	O(n log n)	O(1)
1074. Number of Submatrices That Sum to Target	Go	Hard	O(n^3)	O(n)	❤️
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

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

Title	Solution	Difficulty	Time	Space	收藏
218. The Skyline Problem	Go	Hard	O(n log n)	O(n)	❤️
307. Range Sum Query - Mutable	Go	Hard	O(1)	O(n)
315. Count of Smaller Numbers After Self	Go	Hard	O(n log n)	O(n)
327. Count of Range Sum	Go	Hard	O(n log n)	O(n)	❤️
493. Reverse Pairs	Go	Hard	O(n log n)	O(n)
699. Falling Squares	Go	Hard	O(n log n)	O(n)	❤️
715. Range Module	Go	Hard	O(log n)	O(n)	❤️
732. My Calendar III	Go	Hard	O(log n)	O(n)	❤️
850. Rectangle Area II	Go	Hard	O(n log n)	O(n)	❤️
1157. Online Majority Element In Subarray	Go	Hard	O(log n)	O(n)	❤️
-----------------------------------------------------------------	-------------	-------------	--------------------------	--------------------------	-------------

Binary Indexed Tree

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