LeetCode Records

This is the leetcode code track of Wendi.

Algorithms

Contest

#	Title	Comment	Language
2829	Determine the Minimum Sum of a k-avoiding Array	math	C++
7006	Maximize the Profit as the Salesman	DP,array	C++
2834	Find the Minimum Possible Sum of a Beautiful Array	math	C++

Exercise

#	Title	Comment	Language
0001	Two Sum	hash	C++
0002	Add Two Numbers	C++ pointer	C++
0003	Longest Substring Without Repeating Characters	set, rolling	C++
0004	Median of Two Sorted Arrays	dichotomy	C++
0005	Longest Palindromic Substring	DP (for循环顺序很重要)	C++
0006	ZigZag Conversion	string, loop	C++
0007	Reverse Integer	overflow detection	C++
0008	String to Integer (atoi)	string, automaton	C++
0010	Regular Expression Matching	regular expression (ingenious), string	C++
0011	Container With Most Water	double pointer	C++
0012	Integer to Roman	string	C++
0013	Roman to Integer	string	C++
0014	Longest Common Prefix	string	C++
0015	3Sum	double pointer+	C++
0017	Letter Combinations of a Phone Number	recursion, string	C++
0018	4Sum	double pointer+, hash vector (C++)	C++
0019	Remove Nth Node From End of List	queue, link list	C++
0020	Valid Parentheses	stack	C++
0021	Merge Two Sorted Lists	link list	C++
0022	Generate Parentheses	back trace	C++
0023	Merge k Sorted Lists	merge, link list, prioirity_queue (yyds)	C++
0024	Swap Nodes in Pairs	link list	C++
0025	Reverse Nodes in k-Group	link list	C++
0026	Remove Duplicates from Sorted Array	double pointer	C++
0027	Remove Element	pointer	C++
0028	Implement strStr()	string	Java, C++
0029	Divide Two Integers	bits ops	C++
0030	Substring with Concatenation of All Words	string, hash	C++
0031	Next Permutation	double pointer swap	C++
0032	Longest Valid Parentheses	DP, string	C++
0033	Search in Rotated Sorted Array	binary search	C++
0034	Find First and Last Position of Element in Sorted Array	binary search	C++
0035	Search Insert Position	binary search	C++
0036	Valid Sudoku	matrix	C++
0037	Sudoku Solver	dfs, trace back	C++
0038	Count and Say	string, double pointer	C++
0039	Combination Sum	back trace, recursion	C++
0040	Combination Sum II	recursion, back trace	C++
0041	First Missing Positive	priority_queue (yyds), hash (miserly)	C++
0042	Trapping Rain Water	double pointer (ingenious), DP	C++
0043	Multiply Strings	string ops	C++
0044	Wildcard Matching	regular expression, DP	C++
0045	Jump Game II	DP, BFS	C++
0046	Permutations	recursion, back track	C++
0047	Permutations II	recursion	C++
0048	Rotate Image	matrix transform	C++
0049	Group Anagrams	string, hash	C++
0050	Pow(x, n)	quick pow	C++
0051	N-Queens	back track, recursion	C++
0053	Maximum Subarray	greedy, DP	C++
0054	Spiral Matrix	matrix	C++
0055	Jump Game	DP	C++
0056	Merge Intervals	interval ops, sort	C++
0058	Length of Last Word	string	Java
0059	Spiral Matrix II	matrix	C++
0061	Rotate List	link list	C++
0062	Unique Paths	DP, math	C++
0063	Unique Paths II	DP	Java
0064	Minimum Path Sum	matrix, DP	C++
0066	Plus One	recursion	C++
0067	Add Binary	string	C++
0069	Sqrt(x)	binary search	C++
0070	Climbing Stairs	DP	C++
0071	Simplify Path	string	C++
0072	Edit Distance	DP	C++
0073	Set Matrix Zeroes	matrix	C++
0074	Search a 2D Matrix	matrix	C++
0075	Sort Colors	sort, double pointer	C++
0076	Minimum Window Substring	double pointer, hash	C++
0077	Combinations	recursion	C++
0078	Subsets	recursion	C++
0079	Word Search	string, recursion, DFS	C++
0080	Remove Duplicates from Sorted Array II	double pointer	C++
0081	Search in Rotated Sorted Array II	binary search, sliding	C++
0082	Remove Duplicates from Sorted List II	link list	C++
0083	Remove Duplicates from Sorted List	link list	C++
0084	Largest Rectangle in Histogram	mono stack	C++
0085	Maximal Rectangle	monotonous stack	C++
0086	Partition List	link list	C++
0088	Merge Sorted Array	double pointer	C++
0089	Gray Code	recursion, array	C++
0090	Subsets II	recursion	C++
0091	Decode Ways	DP	C++
0092	Reverse Linked List II	link list	C++
0093	Restore IP Addresses	string, rule	C++
0094	Binary Tree Inorder Traversal	binary tree, inorder	C++
0095	Unique Binary Search Trees II	recursion, binary tree	C++
0096	Unique Binary Search Trees	math, DP	C++
0097	Interleaving String	DP, string	C++
0098	Validate Binary Search Tree	binary tree, recursion	C++
0099	Recover Binary Search Tree	binary tree, inorder traverse	C++
0100	Same Tree	binary tree, recursion	C++
0101	Symmetric Tree	binary tree, recursion	C++
0102	Binary Tree Level Order Traversal	binary tree, queue	C++
0103	Binary Tree Zigzag Level Order Traversal	binary tree, dique	C++
0104	Maximum Depth of Binary Tree	binary tree	C++
0105	Construct Binary Tree from Preorder and Inorder Traversal	binary tree (ingenious), recursion	C++
0107	Binary Tree Level Order Traversal II	binary tree	C++
0108	Convert Sorted Array to Binary Search Tree	binary tree, recursion	C++
0109	Convert Sorted List to Binary Search Tree	link list, binary tree	C++
0110	Balanced Binary Tree	recursion, binary tree	C++
0111	Minimum Depth of Binary Tree	binary tree, recursion	C++
0112	Path Sum	binary tree, recursion	C++
0113	Path Sum II	binary tree, dfs	C++
0115	Distinct Subsequences	DP	C++
0116	Populating Next Right Pointers in Each Node	binary tree, recursion, BFS	C++
0117	Populating Next Right Pointers in Each Node II	binary tree, recursion	C++
0118	Pascal's Triangle	杨辉三角	C++
0119	Pascal's Triangle II杨辉三角	C++
0121	Best Time to Buy and Sell Stock	greedy	C++
0122	Best Time to Buy and Sell Stock II	greedy	C++
0123	Best Time to Buy and Sell Stock III	greedy	C++
0124	Binary Tree Maximum Path Sum	recursion, binary tree	C++
0125	Valid Palindrome	string	C++
0127	Word Ladder	BFS, graph	C++
0128	Longest Consecutive Sequence	greedy, hash	C++
0129	Sum Root to Leaf Numbers	recursion, binary tree	C++
0130	Surrounded Regions	recursion, matrix	C++
0131	Palindrome Partitioning	recursion	C++
0132	Palindrome Partitioning II	DP, string	C++
0134	Gas Station	greedy	C++
0135	Candy	double scan	C++
0136	Single Number	XOR, hash	C++
0138	Copy List with Random Pointer	hash	C++
0139	Word Break	string, DP	C++
0140	Word Break II	recursion	C++
0141	Linked List Cycle	link list, 快慢指针	C++
0142	Linked List Cycle II	link list, 快慢指针	C++
0143	Reorder List	link list	C++
0145	Binary Tree Postorder Traversal	binary tree, traversal, recurion	C++
0148	Sort List	link list, merge sort	C++
0149	Max Points on a Line	hash	C++
0150	Evaluate Reverse Polish Notation	string, stack	C++
0151	Reverse Words in a String	string, stack	C++
0152	Maximum Product Subarray	DP	C++
0153	Find Minimum in Rotated Sorted Array	binary search	C++
0160	Intersection of Two Linked Lists	link list, make cycle	C++
0165	Compare Version Numbers	string	C++, Python
0166	Fraction to Recurring Decimal	string, hash	C++
0168	Excel Sheet Column Title	numbers	C++
0169	Majority Element	Moore vote	C++
0173	Binary Search Tree Iterator	binary tree, queue	C++
0179	Largest Number	string, sort	C++
0188	Best Time to Buy and Sell Stock IV	greedy	C++
0189	Rotate Array	array rotate	C++
0190	Reverse Bits	bit ops	C++
0191	Number of 1 Bits	bit ops	Java, C++
0199	Binary Tree Right Side View	binary tree, queue	C++
0200	Number of Islands	recursion	C++
0203	Remove Linked List Elements	link list	C++
0206	Reverse Linked List	link list	C++
0207	Course Schedule	dfs, graph, topological sort	C++
0209	Minimum Size Subarray Sum	double pointer	C++
0210	Course Schedule II	topological sort, graph	C++
0212	Word Search II	prefix tree, string, backtrace	C++
0213	House Robber II	DP	C++
0215	Kth Largest Element in an Array	heap, quick sort	C++
0216	Combination Sum III	recursion	C++
0217	Contains Duplicate	hash	C++, Java
0218	The Skyline Problem	multiset	C++
0220	Contains Duplicate III	set, lower_bound	C++
0221	Maximal Square	DP	C++
0224	Basic Calculator	stack, string	C++
0226	Invert Binary Tree	binary tree, recursion	C++
0227	Basic Calculator II	string, stack	C++
0232	Implement Queue using Stacks	stack	C++
0234	Palindrome Linked List	link list, reverse ll, fast slow ptr	C++
0235	Lowest Common Ancestor of a Binary Search Tree	binary tree, binary search	C++
0236	Lowest Common Ancestor of a Binary Tree	binary tree, recursion, BFS	C++
0237	Delete Node in a Linked List	link list	C++
0238	Product of Array Except Self	traverse	C++
0240	Search a 2D Matrix II	matrix, pointer	C++
0241	Different Ways to Add Parentheses	string, recursion, DP	C++
0249	Group Shifted Strings	string, map, hash	C++
0253	Meeting Rooms II	min heap	C++
0257	Binary Tree Paths	binary tree, recursion	C++
0259	3Sum Smaller	array, binary search, two pointers	C++
0260	Single Number III	binary ops	C++
0263	Ugly Number	easy	C++
0264	Ugly Number II	trible pointer	C++
0269	Alien Dictionary	topological sort	C++
0273	Integer to English Words	string, recursion	C++
0274	H-Index	sort, count	C++
0277	Find the Celebrity	math	C++
0278	First Bad Version	binary search	C++
0287	Find the Duplicate Number	伪link list环	C++
0289	Game of Life	matrix	C++
0295	Find Median from Data Stream	insert (normal), heap (ingenious)	C++
0298	Binary Tree Longest Consecutive Sequence	binary tree, recursion	C++
0300	Longest Increasing Subsequence	DP, greedy	C++
0309	Best Time to Buy and Sell Stock with Cooldown	greedy	C++
0314	Binary Tree Vertical Order Traversal	hash, BFS, binary tree	C++
0315	Count of Smaller Numbers After Self	binary index tree, get_rank	C++
0316	Remove Duplicate Letters	string, stack	C++
0322	Coin Change	DP	C++
0323	Number of Connected Components in an Undirected Graph	disjoin set	C++
0328	Odd Even Linked List	link list	C++
0329	Longest Increasing Path in a Matrix	recursion, DP	C++
0331	Verify Preorder Serialization of a Binary Tree	binary tree	C++
0333	Largest BST Subtree	binary tree, recursion	C++
0337	House Robber III	recursion, DP	C++
0338	Counting Bits	binary	C++
0339	Nested List Weight Sum	recursion, array	C++
0340	Longest Substring with At Most K Distinct Characters	counter, double pointer	C++
0343	Integer Break	math	C++
0344	Reverse String	string, double pointer	C++
0347	Top K Frequent Elements	counter	C++
0349	Intersection of Two Arrays	hash, set ops	C++
0350	Intersection of Two Arrays II	hash	C++
0354	Russian Doll Envelopes	greedy, binary search (lower_bound)	C++
0363	Max Sum of Rectangle No Larger Than K	double pointer, set, matrix	C++
0366	Find Leaves of Binary Tree	binary tree, recursion	C++
0368	Largest Divisible Subset	DP	C++
0370	Range Addition	partial_sum, array	C++
0377	Combination Sum IV	recursion, DP	C++
0386	Lexicographical Numbers	numbers, recursion	C++
0387	First Unique Character in a String	hash	C++
0388	Longest Absolute File Path	string, recursion, prefix tree	C++
0392	Is Subsequence	string	C++
0393	UTF-8 Validation	string	C++
0394	Decode String	string, stack	C++
0395	Longest Substring with At Least K Repeating Characters	recursion, binary search	C++
0400	Nth Digit	math	C++
0402	Remove K Digits	string	C++
0403	Frog Jump	DP	C++
0406	Queue Reconstruction by Height	insert, sort	C++
0409	Longest Palindrome	string, palindrome	Java
0410	Split Array Largest Sum	binary search	C++
0413	Arithmetic Slices	double pointer	C++
0415	Add Strings	string	C++
0416	Partition Equal Subset Sum	DP	C++
0417	Pacific Atlantic Water Flow	dfs, recursion, matrix	C++
0418	Sentence Screen Fitting	DP, string	C++
0421	Maximum XOR of Two Numbers in an Array	XOR, bit ops, hash	C++
0423	Reconstruct Original Digits from English	hash, map, string	C++
0424	Longest Repeating Character Replacement	string, double pointer	C++
0426	Convert Binary Search Tree to Sorted Doubly Linked List	binary tree, hash, heap	C++
0430	Flatten a Multilevel Doubly Linked List	link list	C++
0435	Non-overlapping Intervals	greedy	C++
0437	Path Sum III	binary tree, hash	C++
0440	K-th Smallest in Lexicographical Order	十叉数	C++
0442	Find All Duplicates in an Array	medium difficulty?	C++
0443	String Compression	string, counter	C++
0445	Add Two Numbers II	link list, stack	C++
0448	Find All Numbers Disappeared in an Array	for loop	C++
0453	Minimum Moves to Equal Array Elements	greedy	C++
0456	132 Pattern	monotonous stack	C++
0459	Repeated Substring Pattern	string	C++
0461	Hamming Distance	binary ops	C++
0470	Implement Rand10() Using Rand7()	random function	C++
0474	Ones and Zeroes	DP, matrix	C++
0482	License Key Formatting	string	C++
0485	Max Consecutive Ones	counter	C++
0487	Max Consecutive Ones II	presum, double pointer	C++
0490	The Maze	matrix, BFS	C++
0498	Diagonal Traverse	matrix	C++
0503	Next Greater Element II	greedy	C++
0509	Fibonacci Number	DP	C++
0518	Coin Change 2	DP	C++
0526	Beautiful Arrangement	backtrace	C++
0529	Minesweeper	recursion, matrix	C++
0532	Continuous Subarray Sum	hash	C++
0540	Single Element in a Sorted Array	binary search	C++
0543	Diameter of Binary Tree	binary tree, recursion	C++
0545	Boundary of Binary Tree	binary tree, recursion	C++
0546	Remove Boxes	DP, recursion	C++
0547	Number of Provinces	disjoint set	C++
0554	Brick Wall	hash, counter	C++
0556	Next Greater Element III	double pointer, #0031	C++
0557	Reverse Words in a String III	string	Java
0560	Subarray Sum Equals K	hash	C++
0567	Permutation in String	string, counter	C++
0593	Valid Square	math	C++
0605	Can Place Flowers	greedy	Java
0611	Valid Triangle Number	double pointer	C++
0616	Add Bold Tag in String	string	C++
0617	Merge Two Binary Trees	binary tree	C++
0628	Maximum Product of Three Numbers	math	C++
0629	K Inverse Pairs Array	DP, array	C++
0630	Course Schedule III	greedy, heap	C++
0633	Sum of Square Numbers	hash, double pointer	C++
0643	Maximum Average Subarray I	sliding window	C++
0645	Set Mismatch	count, XOR (待推敲)	C++
0647	Palindromic Substrings	double pointer	C++
0662	Maximum Width of Binary Tree	binary tree, queue	C++
0664	Strange Printer	string, DP	C++
0665	Non-decreasing Array	recursion, back trace	C++
0666	[Path Sum IV](https://leetcode.com/problems/path-sum-iv/	array, binary tree	C++
0670	Maximum Swap	number	Java
0678	Valid Parenthesis String	string, stack	C++
0679	24 Game	back track, recursion	C++
0680	Valid Palindrome II	double pointer	C++
0681	Next Closest Time	greedy	C++
0690	Employee Importance	recursion, hash	Java, C++
0692	Top K Frequent Words	hash	C++
0694	Number of Distinct Islands	matrix, recursion, hash	C++
0695	Max Area of Island	recursion	C++
0696	Count Binary Substrings	string	C++
0697	Degree of an Array	counter, hash	C++
0698	Partition to K Equal Sum Subsets	DP, back trace	C++
0704	Binary Search	binary search	C++
0718	Maximum Length of Repeated Subarray	DP	C++
0721	Accounts Merge	disjoint set, hash	C++
0723	Candy Crush	matrix, recursion	C++
0735	Asteroid Collision	stack	C++
0739	Daily Temperatures	stack	C++
0740	Delete and Earn	DP, counter	C++
0743	Network Delay Time	BFS	C++
0746	Min Cost Climbing Stairs	DP	C++
0763	Partition Labels	string, unordered_map	C++
0765	Couples Holding Hands	disjoint set	C++
0767	Reorganize String	map, string	C++
0781	Rabbits in Forest	counter (hash)	C++
0787	Cheapest Flights Within K Stops	DP, graph	Java
0792	Number of Matching Subsequences	string, hash	C++
0797	All Paths From Source to Target	graph, BFS, DFS	C++
0799	Champagne Tower	DP, math	C++
0815	Bus Routes	graph, dijkstra, BFS	C++
0819	Most Common Word	string, hash	C++
0832	Flipping an Image	matrix	C++
0853	Car Fleet	math, greedy	C++
0858	Mirror Reflection	math, lcd, gcd	C++
0863	All Nodes Distance K in Binary Tree	binary tree, recursion	C++
0867	Transpose Matrix	matrix	C++
0872	Leaf-Similar Trees	binary tree, dfs	C++
0875	Koko Eating Bananas	binary search	C++
0877	Stone Game	math, DP	C++
0887	Super Egg Drop	DP, math	C++
0897	Increasing Order Search Tree	recursion, binary tree	C++
0909	Snakes and Ladders	matrix, BFS	C++
0912	Sort an Array	quick sort	C++
0921	Minimum Add to Make Parentheses Valid	stack, string	C++
0929	Unique Email Addresses	string	C++
0935	Knight Dialer	DP, graph	C++
0937	Reorder Data in Log Files	string	C++
0939	Minimum Area Rectangle	matrix, hash	C++
0945	Minimum Increment to Make Array Unique	greedy, array	C++
0953	Verifying an Alien Dictionary	string	C++
0973	K Closest Points to Origin	set, nth_element	C++
0981	Time Based Key-Value Store	map, string	C++
0989	Add to Array-Form of Integer	array integer	C++
0994	Rotting Oranges	matrix, BFS	C++
1004	Max Consecutive Ones III	binary search	C++
1010	Pairs of Songs With Total Durations Divisible by 60	hash	C++
1011	Capacity To Ship Packages Within D Days	binary search	C++
1029	Two City Scheduling	array, greedy	C++
1035	Uncrossed Lines	DP	C++
1041	Robot Bounded In Circle	vector	C++
1047	Remove All Adjacent Duplicates In String	string	C++
1048	Longest String Chain	DP, dfs, string	C++
1049	Last Stone Weight II	recursion, DP	C++
1052	Grumpy Bookstore Owner	greedy	C++
1061	Lexicographically Smallest Equivalent String	disjoint set, string	C++
1062	Longest Repeating Substring	string, hash, binary search	C++
1073	Adding Two Negabinary Numbers	array ops	C++
1102	Path With Maximum Minimum Value	matrix, max heap, BFS	C++
1110	Delete Nodes And Return Forest	binary tree, recursion	C++
1120	Maximum Average Subtree	recursion, binary tree	C++
1123	Lowest Common Ancestor of Deepest Leaves	binary tree, recursion	C++
1135	Connecting Cities With Minimum Cost	disjoin set, Kruskal alg	C++
1143	Longest Common Subsequence	string, DP	C++
1151	Minimum Swaps to Group All 1's Together	sliding window, greedy	C++
1152	Analyze User Website Visit Pattern	string, hash	C++
1169	Invalid Transactions	string	C++
1167	Minimum Cost to Connect Sticks	heap, priority_queue	C++
1175	Prime Arrangements	math	C++
1190	Reverse Substrings Between Each Pair of Parentheses	stack, string	C++
1209	Remove All Adjacent Duplicates in String II	stack, string	C++
1236	Web Crawler	recursion, string, hash	C++
1239	Maximum Length of a Concatenated String with Unique Characters	backtrace, set	C++
1249	Minimum Remove to Make Valid Parentheses	string, stack	C++
1250	Check If It Is a Good Array	gcd, math	C++
1268	Search Suggestions System	prefix tree, string, dfs	C++
1274	Number of Ships in a Rectangle	recursion	C++
1277	Count Square Submatrices with All Ones	matrix, DP	C++
1278	Palindrome Partitioning III	DP, string	C++
1305	All Elements in Two Binary Search Trees	binary tree, dfs	C++
1310	XOR Queries of a Subarray	XOR, prefix sum	C++
1318	Minimum Flips to Make a OR b Equal to c	bit ops	C++
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance	graph, Floyd-Warshall's algorithm
1339	Maximum Product of Splitted Binary Tree	binary tree, recursion	C++
1347	Minimum Number of Steps to Make Two Strings Anagram	string, hash	C++
1353	Maximum Number of Events That Can Be Attended	set, map, interval ops, priority queue, greedy	C++
1388	Pizza With 3n Slices	DP, greedy	C++
1411	Number of Ways to Paint N × 3 Grid	找规律	C++
1423	Maximum Points You Can Obtain from Cards	greedy, rolling	C++
1428	Leftmost Column with at Least a One	matrix, binary search	C++
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	monotonous stack, double pointer	C++
1442	Count Triplets That Can Form Two Arrays of Equal XOR	XOR, hash, truble pointer	C++
1444	Number of Ways of Cutting a Pizza	DP, matrix, prefix sum	C++
1462	Course Schedule IV	topological sort	C++
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	greedy	C++
1480	Running Sum of 1d Array	easy	C++, Java
1481	Least Number of Unique Integers after K Removals	hash, counter	C++
1492	The kth Factor of n		C++
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	greedy	C++
1530	Number of Good Leaf Nodes Pairs	binary tree, recursion	C++
1539	Kth Missing Positive Number	pointer	C++
1553	Minimum Number of Days to Eat N Oranges	DP, recursion	C++
1603	Design Parking System	easy	C++
1614	Maximum Nesting Depth of the Parentheses	string	C++
1631	Path With Minimum Effort	matrix, max heap, BFS	C++
1644	Lowest Common Ancestor of a Binary Tree II	binary tree, BFS	C++
1648	Sell Diminishing-Valued Colored Balls	math	C++
1650	Lowest Common Ancestor of a Binary Tree III	hash, recursion, binary tree	C++
1658	Minimum Operations to Reduce X to Zero	prefix sum, greedy, array	C++
1710	Maximum Units on a Truck	hash	C++
1720	Decode XORed Array	XOR	C++
1730	Shortest Path to Get Food	BFS	C++
1734	Decode XORed Permutation	XOR	C++
1744	Can You Eat Your Favorite Candy on Your Favorite Day?	prefix sum	C++
1762	Buildings With an Ocean View	traverse	C++
1787	Make the XOR of All Segments Equal to Zero	XOR, hash, DP	C++
1818	Minimum Absolute Sum Difference	binary search, greedy	C++
1822	Sign of the Product of an Array		C++
1823	Find the Winner of the Circular Game	math	C++
1834	Single-Threaded CPU	priority queue, buffer	C++
1849	Splitting a String Into Descending Consecutive Values	backtrace, recursion	C++
1915	Number of Wonderful Substrings	DP, bitmask	C++
1996	The Number of Weak Characters in the Game	sort	C++
2093	Minimum Cost to Reach City With Discounts	graph, Dijkstra	C++
2094	Finding 3-Digit Even Numbers	array	C++
2095	Delete the Middle Node of a Linked List	link list	C++
2096	Step-By-Step Directions From a Binary Tree Node to Another	binary tree, dfs	C++
2098	Subsequence of Size K With the Largest Even Sum	max heap, array	C++
2099	Find Subsequence of Length K With the Largest Sum	array, max heap	C++
2100	Find Good Days to Rob the Bank	array, monotonous stack, DP	C++
2101	Detonate the Maximum Bombs	graph, bfs	C++
2103	Rings and Rods	string, hash	C++
2104	Sum of Subarray Ranges	array	C++
2105	Watering Plants II	array	C++
2107	Number of Unique Flavors After Sharing K Candies	sliding window, array, hash	C++
2108	Find First Palindromic String in the Array	string	C++
2109	Adding Spaces to a String	string	C++
2110	Number of Smooth Descent Periods of a Stock	array, math	C++
2113	Elements in Array After Removing and Replacing Elements	array	C++
2114	Maximum Number of Words Found in Sentences	string	C++
2115	Find All Possible Recipes from Given Supplies	string, hash	C++
2116	Check if a Parentheses String Can Be Valid	stack, string	C++
2119	A Number After a Double Reversal	math	C++
2120	Execution of All Suffix Instructions Staying in a Grid	string, matrix	C++
2121	Intervals Between Identical Elements	hash, array	C++
2124	Check if All A's Appears Before All B's	string	C++
2125	Number of Laser Beams in a Bank	string	C++
2126	Destroying Asteroids	greedy	C++
2128	Remove All Ones With Row and Column Flips	bit, matrix	C++
2129	Capitalize the Title	string	C++
2130	Maximum Twin Sum of a Linked List	link list	C++
2131	Longest Palindrome by Concatenating Two Letter Words	string, hash	C++
2133	Check if Every Row and Column Contains All Numbers	hash, matrix	C++
2134	Minimum Swaps to Group All 1's Together II	sliding window, array	C++
2135	Count Words Obtained After Adding a Letter	string, bit, binary search	C++
2137	Pour Water Between Buckets to Make Water Levels Equal	binary search	C++
2138	Divide a String Into Groups of Size k	string	C++
2139	Minimum Moves to Reach Target Score	math	C++
2140	Solving Questions With Brainpower	DP	C++
2144	Minimum Cost of Buying Candies With Discount	array, greedy	C++
2145	Count the Hidden Sequences	array, prefix sum	C++
2146	K Highest Ranked Items Within a Price Range	matrix, BFS	C++
2148	Count Elements With Strictly Smaller and Greater Elements	hash, array	C++
2149	Rearrange Array Elements by Sign	array	C++
2150	Find All Lonely Numbers in the Array	hash, array	C++
2152	Minimum Number of Lines to Cover Points	math, DP, recursion	C++
2154	Keep Multiplying Found Values by Two	hash	C++
2155	All Divisions With the Highest Score of a Binary Array	array, prefix sum	C++
2160	Minimum Sum of Four Digit Number After Splitting Digits	math, greedy	C++
2161	Partition Array According to Given Pivot	array	C++
2162	Minimum Cost to Set Cooking Time	math, enumeration	C++
2164	Sort Even and Odd Indices Independently	array	C++
2165	Smallest Value of the Rearranged Number	string, sort	C++
2169	Count Operations to Obtain Zero	math	C++
2170	Minimum Operations to Make the Array Alternating	hash, greedy	C++
2171	Removing Minimum Number of Magic Beans	prefix sum, array	C++
2168	Unique Substrings With Equal Digit Frequency	string, rolling hash	C++
2174	Remove All Ones With Row and Column Flips II	BFS, matrix	C++
2176	Count Equal and Divisible Pairs in an Array	array	C++
2177	Find Three Consecutive Integers That Sum to a Given Number	math	C++
2178	Maximum Split of Positive Even Integers	math, array	C++
2180	Count Integers With Even Digit Sum	math	C++
2181	Merge Nodes in Between Zeros	link list	C++
2182	Construct String With Repeat Limit	string, heap	C++
2184	Number of Ways to Build Sturdy Brick Wall	DP, bit, recursion	C++
2189	Number of Ways to Build House of Cards	DP, recursion	C++
2190	Most Frequent Number Following Key In an Array	array	C++
2191	Sort the Jumbled Numbers	map, array	C++
2192	All Ancestors of a Node in a Directed Acyclic Graph	BFS, graph	C++
2194	Cells in a Range on an Excel Sheet	string	C++
2195	Append K Integers With Minimal Sum	math	C++
2196	Create Binary Tree From Descriptions	binary tree, hash	C++
2198	Number of Single Divisor Triplets	math	C++
2200	Find All K-Distant Indices in an Array	array	C++
2201	Count Artifacts That Can Be Extracted	hash	C++
2202	Maximize the Topmost Element After K Moves	array	C++
2206	Divide Array Into Equal Pairs	array	C++
2207	Maximize Number of Subsequences in a String	greedy, string	C++
2208	Minimum Operations to Halve Array Sum	greedy, heap	C++cm
2210	Count Hills and Valleys in an Array	array	C++
2211	Count Collisions on a Road	stack	C++
2212	Maximum Points in an Archery Competition	backtrace	C++
2214	Minimum Health to Beat Game	greedy	C++
2215	Find the Difference of Two Arrays	hash	C++
2216	Minimum Deletions to Make Array Beautiful	greedy	C++
2217	Find Palindrome With Fixed Length	math, palindrome	C++
2219	Maximum Sum Score of Array	prefix	C++
2220	Minimum Bit Flips to Convert Number	XOR	C++
2221	Find Triangular Sum of an Array	math	C++
2222	Number of Ways to Select Buildings	DP, string	C++
2226	Maximum Candies Allocated to K Children	binary search	C++
2229	Check if an Array Is Consecutive	array	C++
2235	Add Two Integers	simple	C++
2236	Root Equals Sum of Children	binary tree	C++
2237	Count Positions on Street With Required Brightness	interval	C++
2239	Find Closest Number to Zero	array	C++
2240	Number of Ways to Buy Pens and Pencils	enumeration	C++
2250	Count Number of Rectangles Containing Each Point	binary search	C++
2255	Count Prefixes of a Given String	string	C++
2256	Minimum Average Difference	prefix sum	C++
2257	Count Unguarded Cells in the Grid	matrix	C++
2263	Make Array Non-decreasing or Non-increasing	math,max heap	C++
2268	Minimum Number of Keypresses	hash, string	C++
2269	Find the K-Beauty of a Number	string	C++
2270	Number of Ways to Split Array	prefix sum	C++
2271	Maximum White Tiles Covered by a Carpet	interval, prefix sum	C++
2282	Number of People That Can Be Seen in a Grid	binary search, monotonous stack	C++
2283	Check if Number Has Equal Digit Count and Digit Value	hash	C++
2284	Sender With Largest Word Count	hash, max heap	C++
2285	Maximum Total Importance of Roads	max heap, graph	C++
2289	Steps to Make Array Non-decreasing	DP	C++
2305	Fair Distribution of Cookies	backtrace	C++
2369	Check if There is a Valid Partition For The Array	DP	C++
2370	Longest Ideal Subsequence	DP	C++
2375	Construct Smallest Number From DI String	string, greedy	C++
2572	Count the Number of Square-Free Subsets	bit, DP	C++
2864	Maximum Odd Binary Number	string	C++
2894	Divisible and Non-divisible Sums Difference	math	C++
2895	Minimum Processing Time	array	C++
2897	Apply Operations on Array to Maximize Sum of Squares	bit, math	C++
2905	Find Indices With Index and Value Difference II	set, array	C++
2925	Maximum Score After Applying Operations on a Tree	tree, topology	C++
2933	High-Access Employees	string, array	C++
100048	Beautiful Towers II	monotonous stack	C++
100049	Beautiful Towers I	monotonous stack	C++
100142	Make Lexicographically Smallest Array by Swapping Elements	array, map, set	C++
LCP09	最小跳跃次数	BFS	C++
剑03	数组中重复的数字	hash	C++
剑05	替换空格	string	C++
剑07	重建二叉树	binary tree, recursion	C++
剑12	矩阵中的路径	recursion, back trace	C++
剑13	机器人的运动范围	recursion	C++
剑18	删除链表的节点	link list	C++
剑20	表示数值的字符串	string (判断折磨人)	C++
剑21	调整数组顺序使奇数位于偶数前面	double pointer	C++
剑22	链表中倒数第k个节点	link list	C++
剑26	树的子结构	binary tree, recursion	C++
剑27	二叉树的镜像	binary tree, recursion	C++
剑32	I. 从上到下打印二叉树	binary tree, bfs	C++
剑33	二叉搜索树的后序遍历序列	recursion	C++
剑38	字符串的排列	recursion, string	C++
剑42	连续子数组的最大和	greedy, DP	C++
剑45	把数组排成最小的数	string, sort	C++
剑46	把数字翻译成字符串	recursion	C++
剑47	礼物的最大价值	DP	Java
剑50	第一个只出现一次的字符	counter	Java
剑51	数组中的逆序对	merge sort, binary indexed tree	C++
剑53	II. 0～n-1中缺失的数字	binary search	C++
剑56	I. 数组中数字出现的次数	XOR, bits ops	C++
剑57	II. 和为s的连续正数序列	math	C++
剑58	II. 左旋转字符串	string	C++
剑60	n个骰子的点数	DP	C++
剑61	扑克牌中的顺子	playing cards	C++
剑62	圆圈中最后剩下的数字	math	C++
剑64	求1+2+…+n	recursion	C++
剑66	构建乘积数组	DP	C++
剑119	最长连续序列	hash, set	C++
面01.01	Is Unique LCCI	bits ops	C++
面01.06	Compress String LCCI	string, double pointer	C++
面02.02	Kth Node From End of List LCCI	link list	C++
面02.03	Delete Middle Node LCCI	link list	C++
面02.05	链表求和	link list	C++
面08.06	Hanota LCCI	recursion	C++
面08.09	Bracket LCCI	string, recursion	C++
面10.01	Sorted Merge LCCI	merge	C++
面16.14	Best Line LCCI	hash, greedy	C++
面16.19	Pond Sizes LCCI	dfs, recursion	C++
面16.26	Calculator LCCI	string, stack	C++
面17.21	直方图的水量	double pointer	C++
面17.24	Max Submatrix LCCI	greedy, prefix sum, matrix	C++

Data Structure

#	Title	Comment	Language
0146	LRU Cache	link list, hash	C++
0155	Min Stack	stack	C++
0158	Read N Characters Given Read4 II - Call multiple times	buffer	C++
0208	Implement Trie (Prefix Tree)	prefix tree, recursion	C++
0211	Design Add and Search Words Data Structure	prefix tree, recursion	C++
0244	Shortest Word Distance II	hash, string, double pointer	C++
0284	Peeking Iterator	iterator	C++
0303	Range Sum Query - Immutable	prefix sum	C++
0304	Range Sum Query 2D - Immutable	matrix, prefix sum	C++
0307	Range Sum Query - Mutable	Binary Index Tree, array	C++
0341	Flatten Nested List Iterator	dfs	C++
0348	Design Tic-Tac-Toe	game	C++
0359	Logger Rate Limiter	map, hash	C++
0362	Design Hit Counter	queue	C++
0380	Insert Delete GetRandom O(1)	hash, array	C++
0381	Insert Delete GetRandom O(1) - Duplicates allowed	hash, set, array	C++
0384	Shuffle an Array	random	C++
0398	Random Pick Index	hash, map	C++
0428	Serialize and Deserialize N-ary Tree	recursion, dfs, string, stringstream	C++
0528	Random Pick with Weight	binary search, upper_bound	C++
0588	Design In-Memory File System	prefix tree (tries)	C++
0707	Design Linked List	link list	C++
0895	Maximum Frequency Stack	stack, counter, hash	C++
1146	Snapshot Array	hash map	C++
1244	Design A Leaderboard	heap, hash	C++
1352	Product of the Last K Numbers	prefix	C++
1396	Design Underground System	hash, string	C++
1472	Design Browser History	list, iterator	C++
1570	Dot Product of Two Sparse Vectors	hash, vector	C++
1628	Design an Expression Tree With Evaluate Function	stack	C++
1656	Design an Ordered Stream	array	C++
2166	Design Bitset	string	C++
2241	Design an ATM Machine	greedy	C++
剑59	II. 队列的最大值	deque	C++

SQL

#	Title	Comment
0175	Combine Two Tables	OUTER JOIN
0176	Second Highest Salary	nested MAX
0177	Nth Highest Salary	更通用的求第n大的条目的方法
0178	Rank Scores	DENSE_RANK()
0180	Consecutive Numbers	DISTINCT, 根据value的出现频次筛选条目
0181	Employees Earning More Than Their Managers	自连接
0182	Duplicate Emails	只取有重复的元素
0184	Department Highest Salary	MAX from groups
0196	Delete Duplicate Emails	DELETE
0197	Rising Temperature	DATEDIFF
0595	Big Countries
1777	Product's Price for Each Store	SUM, IF
1873	Calculate Special Bonus	IF
2205	The Number of Users That Are Eligible for Discount	BETWEEN, DISTINCT