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LeetCode

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Solutions

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#	Solution	Tags	Difficulty	Remark
0001	Two Sum	Array,Hash Table	Easy
0002	Add Two Numbers	Recursion,Linked List,Math	Medium
0003	Longest Substring Without Repeating Characters	Hash Table,String,Sliding Window	Medium
0004	Median of Two Sorted Arrays	Array,Binary Search,Divide and Conquer	Hard
0005	Longest Palindromic Substring	String,Dynamic Programming	Medium
0006	ZigZag Conversion	String	Medium
0007	Reverse Integer	Math	Easy
0008	String to Integer (atoi)	String	Medium
0009	Palindrome Number	Math	Easy
0010	Regular Expression Matching	Recursion,String,Dynamic Programming	Hard
0011	Container With Most Water	Greedy,Array,Two Pointers	Medium
0012	Integer to Roman	Hash Table,Math,String	Medium
0013	Roman to Integer	Hash Table,Math,String	Easy
0014	Longest Common Prefix	String	Easy
0015	3Sum	Array,Two Pointers,Sorting	Medium
0016	3Sum Closest	Array,Two Pointers,Sorting	Medium
0017	Letter Combinations of a Phone Number	Hash Table,String,Backtracking	Medium
0018	4Sum	Array,Two Pointers,Sorting	Medium
0019	Remove Nth Node From End of List	Linked List,Two Pointers	Medium
0028	Implement strStr()	Two Pointers,String,String Matching	Easy
0039	Combination Sum	Array,Backtracking	Medium
0040	Combination Sum II	Array,Backtracking	Medium
0041	First Missing Positive	Array,Hash Table	Hard
0042	Trapping Rain Water	Stack,Array,Two Pointers,Dynamic Programming,Monotonic Stack	Hard
0043	Multiply Strings	Math,String,Simulation	Medium
0044	Wildcard Matching	Greedy,Recursion,String,Dynamic Programming	Hard
0045	Jump Game II	Greedy,Array,Dynamic Programming	Medium
0046	Permutations	Array,Backtracking	Medium
0047	Permutations II	Array,Backtracking	Medium
0048	Rotate Image	Array,Math,Matrix	Medium
0049	Group Anagrams	Hash Table,String,Sorting	Medium
0050	Pow(x, n)	Recursion,Math	Medium
0051	N-Queens	Array,Backtracking	Hard
0052	N-Queens II	Backtracking	Hard
0053	Maximum Subarray	Array,Divide and Conquer,Dynamic Programming	Easy
0054	Spiral Matrix	Array,Matrix,Simulation	Medium
0055	Jump Game	Greedy,Array,Dynamic Programming	Medium
0056	Merge Intervals	Array,Sorting	Medium
0057	Insert Interval	Array	Medium
0058	Length of Last Word	String	Easy
0059	Spiral Matrix II	Array,Matrix,Simulation	Medium
0060	Permutation Sequence	Recursion,Math	Hard
0061	Rotate List	Linked List,Two Pointers	Medium
0062	Unique Paths	Math,Dynamic Programming,Combinatorics	Medium
0063	Unique Paths II	Array,Dynamic Programming,Matrix	Medium
0064	Minimum Path Sum	Array,Dynamic Programming,Matrix	Medium
0065	Valid Number	String	Hard
0066	Plus One	Array,Math	Easy
0067	Add Binary	Bit Manipulation,Math,String,Simulation	Easy
0068	Text Justification	String,Simulation	Hard
0069	Sqrt(x)	Math,Binary Search	Easy
0070	Climbing Stairs	Memoization,Math,Dynamic Programming	Easy
0084	Largest Rectangle in Histogram	Stack,Array,Monotonic Stack	Hard
0085	Maximal Rectangle	Stack,Array,Dynamic Programming,Matrix,Monotonic Stack	Hard
0086	Partition List	Linked List,Two Pointers	Medium
0087	Scramble String	String,Dynamic Programming	Hard
0088	Merge Sorted Array	Array,Two Pointers,Sorting	Easy
0089	Gray Code	Bit Manipulation,Math,Backtracking	Medium
0090	Subsets II	Bit Manipulation,Array,Backtracking	Medium
0091	Decode Ways	String,Dynamic Programming	Medium
0092	Reverse Linked List II	Linked List	Medium
0093	Restore IP Addresses	String,Backtracking	Medium
0094	Binary Tree Inorder Traversal	Stack,Tree,Depth-First Search,Binary Tree	Easy
0095	Unique Binary Search Trees II	Tree,Binary Search Tree,Dynamic Programming,Backtracking,Binary Tree	Medium
0096	Unique Binary Search Trees	Tree,Binary Search Tree,Math,Dynamic Programming,Binary Tree	Medium
0097	Interleaving String	String,Dynamic Programming	Medium
0098	Validate Binary Search Tree	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Medium
0099	Recover Binary Search Tree	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Medium
0100	Same Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0101	Symmetric Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0102	Binary Tree Level Order Traversal	Tree,Breadth-First Search,Binary Tree	Medium
0103	Binary Tree Zigzag Level Order Traversal	Tree,Breadth-First Search,Binary Tree	Medium
0104	Maximum Depth of Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0105	Construct Binary Tree from Preorder and Inorder Traversal	Tree,Array,Hash Table,Divide and Conquer,Binary Tree	Medium
0106	Construct Binary Tree from Inorder and Postorder Traversal	Tree,Array,Hash Table,Divide and Conquer,Binary Tree	Medium
0107	Binary Tree Level Order Traversal II	Tree,Breadth-First Search,Binary Tree	Medium
0108	Convert Sorted Array to Binary Search Tree	Tree,Binary Search Tree,Array,Divide and Conquer,Binary Tree	Easy
0109	Convert Sorted List to Binary Search Tree	Tree,Binary Search Tree,Linked List,Divide and Conquer,Binary Tree	Medium
0110	Balanced Binary Tree	Tree,Depth-First Search,Binary Tree	Easy
0111	Minimum Depth of Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0112	Path Sum	Tree,Depth-First Search,Binary Tree	Easy
0113	Path Sum II	Tree,Depth-First Search,Backtracking,Binary Tree	Medium
0114	Flatten Binary Tree to Linked List	Stack,Tree,Depth-First Search,Linked List,Binary Tree	Medium
0115	Distinct Subsequences	String,Dynamic Programming	Hard
0116	Populating Next Right Pointers in Each Node	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0117	Populating Next Right Pointers in Each Node II	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0118	Pascal's Triangle	Array,Dynamic Programming	Easy
0119	Pascal's Triangle II	Array,Dynamic Programming	Easy
0133	Clone Graph	Depth-First Search,Breadth-First Search,Graph,Hash Table	Medium
0134	Gas Station	Greedy,Array	Medium
0135	Candy	Greedy,Array	Hard
0136	Single Number	Bit Manipulation,Array	Easy
0137	Single Number II	Bit Manipulation,Array	Medium
0138	Copy List with Random Pointer	Hash Table,Linked List	Medium
0139	Word Break	Trie,Memoization,Hash Table,String,Dynamic Programming	Medium
0140	Word Break II	Trie,Memoization,Hash Table,String,Dynamic Programming,Backtracking	Hard
0141	Linked List Cycle	Hash Table,Linked List,Two Pointers	Easy
0142	Linked List Cycle II	Hash Table,Linked List,Two Pointers	Medium
0143	Reorder List	Stack,Recursion,Linked List,Two Pointers	Medium
0144	Binary Tree Preorder Traversal	Stack,Tree,Depth-First Search,Binary Tree	Easy
0145	Binary Tree Postorder Traversal	Stack,Tree,Depth-First Search,Binary Tree	Easy
0146	LRU Cache	Design,Hash Table,Linked List,Doubly-Linked List	Medium
0147	Insertion Sort List	Linked List,Sorting	Medium
0148	Sort List	Linked List,Two Pointers,Divide and Conquer,Sorting,Merge Sort	Medium
0149	Max Points on a Line	Geometry,Hash Table,Math	Hard
0150	Evaluate Reverse Polish Notation	Stack,Array,Math	Medium
0151	Reverse Words in a String	Two Pointers,String	Medium
0152	Maximum Product Subarray	Array,Dynamic Programming	Medium
0153	Find Minimum in Rotated Sorted Array	Array,Binary Search	Medium
0154	Find Minimum in Rotated Sorted Array II	Array,Binary Search	Hard
0155	Min Stack	Stack,Design	Easy
0156	Binary Tree Upside Down	Tree,Depth-First Search,Binary Tree	Medium	🔒
0157	Read N Characters Given Read4	String,Interactive,Simulation	Easy	🔒
0158	Read N Characters Given Read4 II - Call multiple times	String,Interactive,Simulation	Hard	🔒
0159	Longest Substring with At Most Two Distinct Characters	Hash Table,String,Sliding Window	Medium	🔒
0160	Intersection of Two Linked Lists	Hash Table,Linked List,Two Pointers	Easy
0161	One Edit Distance	Two Pointers,String	Medium	🔒
0162	Find Peak Element	Array,Binary Search	Medium
0163	Missing Ranges	Array	Easy	🔒
0164	Maximum Gap	Array,Bucket Sort,Radix Sort,Sorting	Hard
0165	Compare Version Numbers	Two Pointers,String	Medium
0166	Fraction to Recurring Decimal	Hash Table,Math,String	Medium
0167	Two Sum II - Input array is sorted	Array,Two Pointers,Binary Search	Easy
0168	Excel Sheet Column Title	Math,String	Easy
0169	Majority Element	Array,Hash Table,Divide and Conquer,Counting,Sorting	Easy
0204	Count Primes	Array,Math,Enumeration,Number Theory	Medium
0214	Shortest Palindrome	String,String Matching,Hash Function,Rolling Hash	Hard
0222	Count Complete Tree Nodes	Tree,Depth-First Search,Binary Search,Binary Tree	Medium
0232	Implement Queue using Stacks	Stack,Design,Queue	Easy
0240	Search a 2D Matrix II	Array,Binary Search,Divide and Conquer,Matrix	Medium
0247	Strobogrammatic Number II	Recursion,Array,String	Medium	🔒
0280	Wiggle Sort	Greedy,Array,Sorting	Medium	🔒
0281	Zigzag Iterator	Design,Queue,Array,Iterator	Medium	🔒
0282	Expression Add Operators	Math,String,Backtracking	Hard
0283	Move Zeroes	Array,Two Pointers	Easy
0284	Peeking Iterator	Design,Array,Iterator	Medium
0285	Inorder Successor in BST	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Medium	🔒
0286	Walls and Gates	Breadth-First Search,Array,Matrix	Medium	🔒
0287	Find the Duplicate Number	Bit Manipulation,Array,Two Pointers,Binary Search	Medium
0288	Unique Word Abbreviation	Design,Array,Hash Table,String	Medium	🔒
0289	Game of Life	Array,Matrix,Simulation	Medium
0290	Word Pattern	Hash Table,String	Easy
0291	Word Pattern II	Hash Table,String,Backtracking	Medium	🔒
0292	Nim Game	Brainteaser,Math,Game Theory	Easy
0293	Flip Game	String	Easy	🔒
0294	Flip Game II	Memoization,Math,Dynamic Programming,Backtracking,Game Theory	Medium	🔒
0295	Find Median from Data Stream	Design,Two Pointers,Data Stream,Sorting,Heap (Priority Queue)	Hard
0296	Best Meeting Point	Array,Math,Matrix,Sorting	Hard	🔒
0297	Serialize and Deserialize Binary Tree	Tree,Depth-First Search,Breadth-First Search,Design,String,Binary Tree	Hard
0298	Binary Tree Longest Consecutive Sequence	Tree,Depth-First Search,Binary Tree	Medium	🔒
0299	Bulls and Cows	Hash Table,String,Counting	Medium
0300	Longest Increasing Subsequence	Array,Binary Search,Dynamic Programming	Medium
0301	Remove Invalid Parentheses	Breadth-First Search,String,Backtracking	Hard
0302	Smallest Rectangle Enclosing Black Pixels	Depth-First Search,Breadth-First Search,Array,Binary Search,Matrix	Hard	🔒
0303	Range Sum Query - Immutable	Design,Array,Prefix Sum	Easy
0304	Range Sum Query 2D - Immutable	Design,Array,Matrix,Prefix Sum	Medium
0305	Number of Islands II	Union Find,Array	Hard	🔒
0306	Additive Number	String,Backtracking	Medium
0307	Range Sum Query - Mutable	Design,Binary Indexed Tree,Segment Tree,Array	Medium
0308	Range Sum Query 2D - Mutable	Design,Binary Indexed Tree,Segment Tree,Array,Matrix	Hard	🔒
0309	Best Time to Buy and Sell Stock with Cooldown	Array,Dynamic Programming	Medium
0310	Minimum Height Trees	Depth-First Search,Breadth-First Search,Graph,Topological Sort	Medium
0311	Sparse Matrix Multiplication	Array,Hash Table,Matrix	Medium	🔒
0312	Burst Balloons	Array,Dynamic Programming	Hard
0313	Super Ugly Number	Array,Hash Table,Math,Dynamic Programming,Heap (Priority Queue)	Medium
0314	Binary Tree Vertical Order Traversal	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium	🔒
0315	Count of Smaller Numbers After Self	Binary Indexed Tree,Segment Tree,Array,Binary Search,Divide and Conquer,Ordered Set,Merge Sort	Hard
0316	Remove Duplicate Letters	Stack,Greedy,String,Monotonic Stack	Medium
0317	Shortest Distance from All Buildings	Breadth-First Search,Array,Matrix	Hard	🔒
0318	Maximum Product of Word Lengths	Bit Manipulation,Array,String	Medium
0319	Bulb Switcher	Brainteaser,Math	Medium
0320	Generalized Abbreviation	Bit Manipulation,String,Backtracking	Medium	🔒
0330	Patching Array	Greedy,Array	Hard
0414	Third Maximum Number	Array,Sorting	Easy
0427	Construct Quad Tree	Tree,Array,Divide and Conquer,Matrix	Medium
0428	Serialize and Deserialize N-ary Tree	Tree,Depth-First Search,Breadth-First Search,String	Hard	🔒
0429	N-ary Tree Level Order Traversal	Tree,Breadth-First Search	Medium
0430	Flatten a Multilevel Doubly Linked List	Depth-First Search,Linked List,Doubly-Linked List	Medium
0431	Encode N-ary Tree to Binary Tree	Tree,Depth-First Search,Breadth-First Search,Design,Binary Tree	Hard	🔒
0441	Arranging Coins	Math,Binary Search	Easy
0464	Can I Win	Bit Manipulation,Memoization,Math,Dynamic Programming,Bitmask,Game Theory	Medium
0467	Unique Substrings in Wraparound String	String,Dynamic Programming	Medium
0468	Validate IP Address	String	Medium
0469	Convex Polygon	Geometry,Math	Medium	🔒
0470	Implement Rand10() Using Rand7()	Math,Rejection Sampling,Probability and Statistics,Randomized	Medium
0471	Encode String with Shortest Length	String,Dynamic Programming	Hard	🔒
0472	Concatenated Words	Depth-First Search,Trie,String,Dynamic Programming	Hard
0473	Matchsticks to Square	Bit Manipulation,Array,Dynamic Programming,Backtracking,Bitmask	Medium
0474	Ones and Zeroes	Array,String,Dynamic Programming	Medium
0475	Heaters	Array,Binary Search,Sorting	Medium
0476	Number Complement	Bit Manipulation	Easy
0492	Construct the Rectangle	Math	Easy
0493	Reverse Pairs	Binary Indexed Tree,Segment Tree,Array,Binary Search,Divide and Conquer,Ordered Set,Merge Sort	Hard
0494	Target Sum	Array,Dynamic Programming,Backtracking	Medium
0495	Teemo Attacking	Array,Simulation	Easy
0496	Next Greater Element I	Stack,Array,Hash Table,Monotonic Stack	Easy
0498	Diagonal Traverse	Array,Matrix,Simulation	Medium
0499	The Maze III	Depth-First Search,Breadth-First Search,Graph,Shortest Path,Heap (Priority Queue)	Hard	🔒
0500	Keyboard Row	Array,Hash Table,String	Easy
0501	Find Mode in Binary Search Tree	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Easy
0502	IPO	Greedy,Array,Sorting,Heap (Priority Queue)	Hard
0503	Next Greater Element II	Stack,Array,Monotonic Stack	Medium
0504	Base 7	Math	Easy
0505	The Maze II	Depth-First Search,Breadth-First Search,Graph,Shortest Path,Heap (Priority Queue)	Medium	🔒
0506	Relative Ranks	Array,Sorting,Heap (Priority Queue)	Easy
0507	Perfect Number	Math	Easy
0508	Most Frequent Subtree Sum	Tree,Depth-First Search,Hash Table,Binary Tree	Medium
0509	Fibonacci Number	Recursion,Memoization,Math,Dynamic Programming	Easy
0510	Inorder Successor in BST II	Tree,Binary Search Tree,Binary Tree	Medium	🔒
0511	Game Play Analysis I	Database	Easy	🔒
0513	Find Bottom Left Tree Value	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0514	Freedom Trail	Depth-First Search,Breadth-First Search,String,Dynamic Programming	Hard
0515	Find Largest Value in Each Tree Row	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0516	Longest Palindromic Subsequence	String,Dynamic Programming	Medium
0517	Super Washing Machines	Greedy,Array	Hard
0518	Coin Change 2	Array,Dynamic Programming	Medium
0520	Detect Capital	String	Easy
0521	Longest Uncommon Subsequence I	String	Easy
0522	Longest Uncommon Subsequence II	Array,Hash Table,Two Pointers,String,Sorting	Medium
0523	Continuous Subarray Sum	Array,Hash Table,Math,Prefix Sum	Medium
0524	Longest Word in Dictionary through Deleting	Array,Two Pointers,String,Sorting	Medium
0525	Contiguous Array	Array,Hash Table,Prefix Sum	Medium
0526	Beautiful Arrangement	Bit Manipulation,Array,Dynamic Programming,Backtracking,Bitmask	Medium
0527	Word Abbreviation	Greedy,Trie,Array,String,Sorting	Hard	🔒
0529	Minesweeper	Depth-First Search,Breadth-First Search,Array,Matrix	Medium
0530	Minimum Absolute Difference in BST	Tree,Depth-First Search,Breadth-First Search,Binary Search Tree,Binary Tree	Easy
0558	Logical OR of Two Binary Grids Represented as Quad-Trees	Tree,Divide and Conquer	Medium
0559	Maximum Depth of N-ary Tree	Tree,Depth-First Search,Breadth-First Search	Easy
0563	Binary Tree Tilt	Tree,Depth-First Search,Binary Tree	Easy
0564	Find the Closest Palindrome	Math,String	Hard
0565	Array Nesting	Depth-First Search,Array	Medium
0566	Reshape the Matrix	Array,Matrix,Simulation	Easy
0567	Permutation in String	Hash Table,Two Pointers,String,Sliding Window	Medium
0568	Maximum Vacation Days	Array,Dynamic Programming,Matrix	Hard	🔒
0569	Median Employee Salary	Database	Hard	🔒
0570	Managers with at Least 5 Direct Reports	Database	Medium	🔒
0571	Find Median Given Frequency of Numbers	Database	Hard	🔒
0572	Subtree of Another Tree	Tree,Depth-First Search,Binary Tree,String Matching,Hash Function	Easy
0573	Squirrel Simulation	Array,Math	Medium	🔒
0574	Winning Candidate	Database	Medium	🔒
0575	Distribute Candies	Array,Hash Table	Easy
0576	Out of Boundary Paths	Dynamic Programming	Medium
0577	Employee Bonus	Database	Easy	🔒
0578	Get Highest Answer Rate Question	Database	Medium	🔒
0579	Find Cumulative Salary of an Employee	Database	Hard	🔒
0580	Count Student Number in Departments	Database	Medium	🔒
0581	Shortest Unsorted Continuous Subarray	Stack,Greedy,Array,Two Pointers,Sorting,Monotonic Stack	Medium
0582	Kill Process	Tree,Depth-First Search,Breadth-First Search,Array,Hash Table	Medium	🔒
0583	Delete Operation for Two Strings	String,Dynamic Programming	Medium
0588	Design In-Memory File System	Design,Trie,Hash Table,String	Hard	🔒
0589	N-ary Tree Preorder Traversal	Stack,Tree,Depth-First Search	Easy
0590	N-ary Tree Postorder Traversal	Stack,Tree,Depth-First Search	Easy
0599	Minimum Index Sum of Two Lists	Array,Hash Table,String	Easy
0600	Non-negative Integers without Consecutive Ones	Dynamic Programming	Hard
0601	Human Traffic of Stadium	Database	Hard
0602	Friend Requests II Who Has the Most Friends	Database	Medium	🔒
0603	Consecutive Available Seats	Database	Easy	🔒
0604	Design Compressed String Iterator	Design,Array,Hash Table,String,Iterator	Easy	🔒
0605	Can Place Flowers	Greedy,Array	Easy
0606	Construct String from Binary Tree	Tree,Depth-First Search,String,Binary Tree	Easy
0607	Sales Person	Database	Easy	🔒
0608	Tree Node	Database	Medium	🔒
0609	Find Duplicate File in System	Array,Hash Table,String	Medium
0610	Triangle Judgement	Database	Easy	🔒
0611	Valid Triangle Number	Greedy,Array,Two Pointers,Binary Search,Sorting	Medium
0612	Shortest Distance in a Plane	Database	Medium	🔒
0613	Shortest Distance in a Line	Database	Easy	🔒
0614	Second Degree Follower	Database	Medium	🔒
0615	Average Salary Departments VS Company	Database	Hard	🔒
0616	Add Bold Tag in String	Trie,Array,Hash Table,String,String Matching	Medium	🔒
0617	Merge Two Binary Trees	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0618	Students Report By Geography	Database	Hard	🔒
0619	Biggest Single Number	Database	Easy	🔒
0620	Not Boring Movies	Database	Easy
0621	Task Scheduler	Greedy,Array,Hash Table,Counting,Sorting,Heap (Priority Queue)	Medium
0623	Add One Row to Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0624	Maximum Distance in Arrays	Greedy,Array	Medium	🔒
0625	Minimum Factorization	Greedy,Math	Medium	🔒
0626	Exchange Seats	Database	Medium
0627	Swap Salary	Database	Easy
0628	Maximum Product of Three Numbers	Array,Math,Sorting	Easy
0629	K Inverse Pairs Array	Dynamic Programming	Hard
0630	Course Schedule III	Greedy,Array,Heap (Priority Queue)	Hard
0631	Design Excel Sum Formula	Graph,Design,Topological Sort	Hard	🔒
0632	Smallest Range Covering Elements from K Lists	Greedy,Array,Hash Table,Sorting,Sliding Window,Heap (Priority Queue)	Hard
0633	Sum of Square Numbers	Math,Two Pointers,Binary Search	Medium
0634	Find the Derangement of An Array	Math,Dynamic Programming	Medium	🔒
0635	Design Log Storage System	Design,Hash Table,String,Ordered Set	Medium	🔒
0636	Exclusive Time of Functions	Stack,Array	Medium
0637	Average of Levels in Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0638	Shopping Offers	Bit Manipulation,Memoization,Array,Dynamic Programming,Backtracking,Bitmask	Medium
0639	Decode Ways II	String,Dynamic Programming	Hard
0640	Solve the Equation	Math,String,Simulation	Medium
0642	Design Search Autocomplete System	Design,Trie,String,Data Stream	Hard	🔒
0643	Maximum Average Subarray I	Array,Sliding Window	Easy
0644	Maximum Average Subarray II	Array,Binary Search	Hard	🔒
0645	Set Mismatch	Bit Manipulation,Array,Hash Table,Sorting	Easy
0646	Maximum Length of Pair Chain	Greedy,Array,Dynamic Programming,Sorting	Medium
0647	Palindromic Substrings	String,Dynamic Programming	Medium
0648	Replace Words	Trie,Array,Hash Table,String	Medium
0649	Dota2 Senate	Greedy,Queue,String	Medium
0650	2 Keys Keyboard	Math,Dynamic Programming	Medium
0651	4 Keys Keyboard	Math,Dynamic Programming	Medium	🔒
0652	Find Duplicate Subtrees	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0653	Two Sum IV - Input is a BST	Tree,Depth-First Search,Breadth-First Search,Binary Search Tree,Hash Table,Two Pointers,Binary Tree	Easy
0654	Maximum Binary Tree	Stack,Tree,Array,Divide and Conquer,Binary Tree,Monotonic Stack	Medium
0655	Print Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0656	Coin Path	Array,Dynamic Programming	Hard	🔒
0657	Robot Return to Origin	String,Simulation	Easy
0658	Find K Closest Elements	Array,Two Pointers,Binary Search,Sorting,Heap (Priority Queue)	Medium
0659	Split Array into Consecutive Subsequences	Greedy,Array,Hash Table,Heap (Priority Queue)	Medium
0660	Remove 9	Math	Hard	🔒
0661	Image Smoother	Array,Matrix	Easy
0662	Maximum Width of Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0663	Equal Tree Partition	Tree,Depth-First Search,Binary Tree	Medium	🔒
0664	Strange Printer	String,Dynamic Programming	Hard
0665	Non-decreasing Array	Array	Medium
0666	Path Sum IV	Tree,Depth-First Search,Array,Binary Tree	Medium	🔒
0667	Beautiful Arrangement II	Array,Math	Medium
0668	Kth Smallest Number in Multiplication Table	Binary Search	Hard
0669	Trim a Binary Search Tree	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Medium
0670	Maximum Swap	Greedy,Math	Medium
0671	Second Minimum Node In a Binary Tree	Tree,Depth-First Search,Binary Tree	Easy
0672	Bulb Switcher II	Bit Manipulation,Depth-First Search,Breadth-First Search,Math	Medium
0673	Number of Longest Increasing Subsequence	Binary Indexed Tree,Segment Tree,Array,Dynamic Programming	Medium
0674	Longest Continuous Increasing Subsequence	Array	Easy
0675	Cut Off Trees for Golf Event	Breadth-First Search,Array,Matrix,Heap (Priority Queue)	Hard
0676	Implement Magic Dictionary	Design,Trie,Hash Table,String	Medium
0677	Map Sum Pairs	Design,Trie,Hash Table,String	Medium
0678	Valid Parenthesis String	Stack,Greedy,String,Dynamic Programming	Medium
0679	24 Game	Array,Math,Backtracking	Hard
0680	Valid Palindrome II	Greedy,Two Pointers,String	Easy
0681	Next Closest Time	String,Enumeration	Medium	🔒
0682	Baseball Game	Stack,Array,Simulation	Easy
0683	K Empty Slots	Binary Indexed Tree,Array,Ordered Set,Sliding Window	Hard	🔒
0684	Redundant Connection	Depth-First Search,Breadth-First Search,Union Find,Graph	Medium
0685	Redundant Connection II	Depth-First Search,Breadth-First Search,Union Find,Graph	Hard
0686	Repeated String Match	String,String Matching	Medium
0687	Longest Univalue Path	Tree,Depth-First Search,Binary Tree	Medium
0700	Search in a Binary Search Tree	Tree,Binary Search Tree,Binary Tree	Easy
0701	Insert into a Binary Search Tree	Tree,Binary Search Tree,Binary Tree	Medium
0702	Search in a Sorted Array of Unknown Size	Array,Binary Search,Interactive	Medium	🔒
0703	Kth Largest Element in a Stream	Tree,Design,Binary Search Tree,Binary Tree,Data Stream,Heap (Priority Queue)	Easy
0704	Binary Search	Array,Binary Search	Easy
0709	To Lower Case	String	Easy
0710	Random Pick with Blacklist	Hash Table,Math,Binary Search,Sorting,Randomized	Hard
0713	Subarray Product Less Than K	Array,Sliding Window	Medium
0714	Best Time to Buy and Sell Stock with Transaction Fee	Greedy,Array,Dynamic Programming	Medium
0715	Range Module	Design,Segment Tree,Ordered Set	Hard
0716	Max Stack	Stack,Design,Linked List,Doubly-Linked List,Ordered Set	Easy	🔒
0717	1-bit and 2-bit Characters	Array	Easy
0718	Maximum Length of Repeated Subarray	Array,Binary Search,Dynamic Programming,Sliding Window,Hash Function,Rolling Hash	Medium
0719	Find K-th Smallest Pair Distance	Array,Two Pointers,Binary Search,Sorting	Hard
0720	Longest Word in Dictionary	Trie,Array,Hash Table,String,Sorting	Easy
0721	Accounts Merge	Depth-First Search,Breadth-First Search,Union Find,Array,String	Medium
0722	Remove Comments	Array,String	Medium
0723	Candy Crush	Array,Two Pointers,Matrix,Simulation	Medium	🔒
0724	Find Pivot Index	Array,Prefix Sum	Easy
0725	Split Linked List in Parts	Linked List	Medium
0726	Number of Atoms	Stack,Hash Table,String	Hard
0727	Minimum Window Subsequence	String,Dynamic Programming,Sliding Window	Hard	🔒
0728	Self Dividing Numbers	Math	Easy
0729	My Calendar I	Design,Segment Tree,Ordered Set	Medium
0730	Count Different Palindromic Subsequences	String,Dynamic Programming	Hard
0731	My Calendar II	Design,Segment Tree,Ordered Set	Medium
0732	My Calendar III	Design,Segment Tree,Ordered Set	Hard
0733	Flood Fill	Depth-First Search,Breadth-First Search,Array,Matrix	Easy
0734	Sentence Similarity	Array,Hash Table,String	Easy	🔒
0735	Asteroid Collision	Stack,Array	Medium
0736	Parse Lisp Expression	Stack,Recursion,Hash Table,String	Hard
0737	Sentence Similarity II	Depth-First Search,Breadth-First Search,Union Find,Array,Hash Table,String	Medium	🔒
0738	Monotone Increasing Digits	Greedy,Math	Medium
0739	Daily Temperatures	Stack,Array,Monotonic Stack	Medium
0740	Delete and Earn	Array,Hash Table,Dynamic Programming	Medium
0741	Cherry Pickup	Array,Dynamic Programming,Matrix	Hard
0742	Closest Leaf in a Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium	🔒
0743	Network Delay Time	Depth-First Search,Breadth-First Search,Graph,Shortest Path,Heap (Priority Queue)	Medium
0744	Find Smallest Letter Greater Than Target	Array,Binary Search	Easy
0745	Prefix and Suffix Search	Design,Trie,String	Hard
0746	Min Cost Climbing Stairs	Array,Dynamic Programming	Easy
0747	Largest Number At Least Twice of Others	Array,Sorting	Easy
0761	Special Binary String	Recursion,String	Hard
0762	Prime Number of Set Bits in Binary Representation	Bit Manipulation,Math	Easy
0763	Partition Labels	Greedy,Hash Table,Two Pointers,String	Medium
0764	Largest Plus Sign	Array,Dynamic Programming	Medium
0765	Couples Holding Hands	Greedy,Depth-First Search,Breadth-First Search,Union Find,Graph	Hard
0766	Toeplitz Matrix	Array,Matrix	Easy
0767	Reorganize String	Greedy,Hash Table,String,Counting,Sorting,Heap (Priority Queue)	Medium
0768	Max Chunks To Make Sorted II	Stack,Greedy,Array,Sorting,Monotonic Stack	Hard
0769	Max Chunks To Make Sorted	Stack,Greedy,Array,Sorting,Monotonic Stack	Medium
0770	Basic Calculator IV	Stack,Recursion,Hash Table,Math,String	Hard
0771	Jewels and Stones	Hash Table,String	Easy
0772	Basic Calculator III	Stack,Recursion,Math,String	Hard	🔒
0773	Sliding Puzzle	Breadth-First Search,Array,Matrix	Hard
0774	Minimize Max Distance to Gas Station	Array,Binary Search	Hard	🔒
0775	Global and Local Inversions	Array,Math	Medium
0776	Split BST	Tree,Binary Search Tree,Recursion,Binary Tree	Medium	🔒
0777	Swap Adjacent in LR String	Two Pointers,String	Medium
0778	Swim in Rising Water	Depth-First Search,Breadth-First Search,Union Find,Array,Binary Search,Matrix,Heap (Priority Queue)	Hard
0779	K-th Symbol in Grammar	Bit Manipulation,Recursion,Math	Medium
0780	Reaching Points	Math	Hard
0781	Rabbits in Forest	Greedy,Hash Table,Math	Medium
0782	Transform to Chessboard	Bit Manipulation,Array,Math,Matrix	Hard
0789	Escape The Ghosts	Array,Math	Medium
0842	Split Array into Fibonacci Sequence	String,Backtracking	Medium
0852	Peak Index in a Mountain Array	Array,Binary Search	Easy
0860	Lemonade Change	Greedy,Array	Easy
0861	Score After Flipping Matrix	Greedy,Bit Manipulation,Array,Matrix	Medium
0862	Shortest Subarray with Sum at Least K	Queue,Array,Binary Search,Prefix Sum,Sliding Window,Monotonic Queue,Heap (Priority Queue)	Hard
0863	All Nodes Distance K in Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
0864	Shortest Path to Get All Keys	Bit Manipulation,Breadth-First Search	Hard
0865	Smallest Subtree with all the Deepest Nodes	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium
0866	Prime Palindrome	Math	Medium
0867	Transpose Matrix	Array,Matrix,Simulation	Easy
0868	Binary Gap	Bit Manipulation,Math	Easy
0869	Reordered Power of 2	Math,Counting,Enumeration,Sorting	Medium
0870	Advantage Shuffle	Greedy,Array,Sorting	Medium
0871	Minimum Number of Refueling Stops	Greedy,Array,Dynamic Programming,Heap (Priority Queue)	Hard
0872	Leaf-Similar Trees	Tree,Depth-First Search,Binary Tree	Easy
0873	Length of Longest Fibonacci Subsequence	Array,Hash Table,Dynamic Programming	Medium
0874	Walking Robot Simulation	Array,Simulation	Medium
0882	Reachable Nodes In Subdivided Graph	Graph,Shortest Path,Heap (Priority Queue)	Hard
0894	All Possible Full Binary Trees	Tree,Recursion,Memoization,Dynamic Programming,Binary Tree	Medium
0906	Super Palindromes	Math,Enumeration	Hard
0910	Smallest Range II	Greedy,Array,Math,Sorting	Medium
0911	Online Election	Design,Array,Hash Table,Binary Search	Medium
0912	Sort an Array	Array,Divide and Conquer,Bucket Sort,Counting Sort,Radix Sort,Sorting,Heap (Priority Queue),Merge Sort	Medium
0913	Cat and Mouse	Breadth-First Search,Graph,Memoization,Math,Dynamic Programming,Game Theory	Hard
0914	X of a Kind in a Deck of Cards	Array,Hash Table,Math,Counting,Number Theory	Easy
0915	Partition Array into Disjoint Intervals	Array	Medium
0916	Word Subsets	Array,Hash Table,String	Medium
0917	Reverse Only Letters	Two Pointers,String	Easy
0918	Maximum Sum Circular Subarray	Queue,Array,Divide and Conquer,Dynamic Programming,Monotonic Queue	Medium
0919	Complete Binary Tree Inserter	Tree,Breadth-First Search,Design,Binary Tree	Medium
0923	3Sum With Multiplicity	Array,Hash Table,Two Pointers,Counting,Sorting	Medium
0924	Minimize Malware Spread	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Hard
0925	Long Pressed Name	Two Pointers,String	Easy
0926	Flip String to Monotone Increasing	String,Dynamic Programming	Medium
0927	Three Equal Parts	Array,Math	Hard
0928	Minimize Malware Spread II	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Hard
0929	Unique Email Addresses	Array,Hash Table,String	Easy
0930	Binary Subarrays With Sum	Array,Hash Table,Prefix Sum,Sliding Window	Medium
0931	Minimum Falling Path Sum	Array,Dynamic Programming,Matrix	Medium
0932	Beautiful Array	Array,Math,Divide and Conquer	Medium
0933	Number of Recent Calls	Design,Queue,Data Stream	Easy
0934	Shortest Bridge	Depth-First Search,Breadth-First Search,Array,Matrix	Medium
0935	Knight Dialer	Dynamic Programming	Medium
0936	Stamping The Sequence	Stack,Greedy,Queue,String	Hard
0937	Reorder Data in Log Files	Array,String,Sorting	Easy
0938	Range Sum of BST	Tree,Depth-First Search,Binary Search Tree,Binary Tree	Easy
0939	Minimum Area Rectangle	Geometry,Array,Hash Table,Math,Sorting	Medium
0940	Distinct Subsequences II	String,Dynamic Programming	Hard
0941	Valid Mountain Array	Array	Easy
0942	DI String Match	Greedy,Array,Math,Two Pointers,String	Easy
0943	Find the Shortest Superstring	Bit Manipulation,Array,String,Dynamic Programming,Bitmask	Hard
0944	Delete Columns to Make Sorted	Array,String	Easy
0945	Minimum Increment to Make Array Unique	Greedy,Array,Counting,Sorting	Medium
0946	Validate Stack Sequences	Stack,Array,Simulation	Medium
0947	Most Stones Removed with Same Row or Column	Depth-First Search,Union Find,Graph	Medium
0948	Bag of Tokens	Greedy,Array,Two Pointers,Sorting	Medium
0949	Largest Time for Given Digits	String,Enumeration	Medium
0950	Reveal Cards In Increasing Order	Queue,Array,Sorting,Simulation	Medium
0951	Flip Equivalent Binary Trees	Tree,Depth-First Search,Binary Tree	Medium
0952	Largest Component Size by Common Factor	Union Find,Array,Math	Hard
0953	Verifying an Alien Dictionary	Array,Hash Table,String	Easy
0954	Array of Doubled Pairs	Greedy,Array,Hash Table,Sorting	Medium
0955	Delete Columns to Make Sorted II	Greedy,Array,String	Medium
0956	Tallest Billboard	Array,Dynamic Programming	Hard
0957	Prison Cells After N Days	Bit Manipulation,Array,Hash Table,Math	Medium
0958	Check Completeness of a Binary Tree	Tree,Breadth-First Search,Binary Tree	Medium
0959	Regions Cut By Slashes	Depth-First Search,Breadth-First Search,Union Find,Graph	Medium
0960	Delete Columns to Make Sorted III	Array,String,Dynamic Programming	Hard
0961	N-Repeated Element in Size 2N Array	Array,Hash Table	Easy
0962	Maximum Width Ramp	Stack,Array,Monotonic Stack	Medium
0963	Minimum Area Rectangle II	Geometry,Array,Math	Medium
0964	Least Operators to Express Number	Math,Dynamic Programming	Hard
0965	Univalued Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Easy
0966	Vowel Spellchecker	Array,Hash Table,String	Medium
0967	Numbers With Same Consecutive Differences	Breadth-First Search,Backtracking	Medium
0968	Binary Tree Cameras	Tree,Depth-First Search,Dynamic Programming,Binary Tree	Hard
0969	Pancake Sorting	Greedy,Array,Two Pointers,Sorting	Medium
0983	Minimum Cost For Tickets	Array,Dynamic Programming	Medium
0994	Rotting Oranges	Breadth-First Search,Array,Matrix	Medium
1001	Grid Illumination	Array,Hash Table	Hard
1002	Find Common Characters	Array,Hash Table,String	Easy
1003	Check If Word Is Valid After Substitutions	Stack,String	Medium
1004	Max Consecutive Ones III	Array,Binary Search,Prefix Sum,Sliding Window	Medium
1005	Maximize Sum Of Array After K Negations	Greedy,Array,Sorting	Easy
1006	Clumsy Factorial	Stack,Math,Simulation	Medium
1007	Minimum Domino Rotations For Equal Row	Greedy,Array	Medium
1008	Construct Binary Search Tree from Preorder Traversal	Stack,Tree,Binary Search Tree,Array,Binary Tree,Monotonic Stack	Medium
1009	Complement of Base 10 Integer	Bit Manipulation	Easy
1010	Pairs of Songs With Total Durations Divisible by 60	Array,Hash Table,Counting	Medium
1011	Capacity To Ship Packages Within D Days	Greedy,Array,Binary Search	Medium
1012	Numbers With Repeated Digits	Math,Dynamic Programming	Hard
1025	Divisor Game	Brainteaser,Math,Dynamic Programming,Game Theory	Easy
1026	Maximum Difference Between Node and Ancestor	Tree,Depth-First Search,Binary Tree	Medium
1027	Longest Arithmetic Subsequence	Array,Hash Table,Binary Search,Dynamic Programming	Medium
1028	Recover a Tree From Preorder Traversal	Tree,Depth-First Search,String,Binary Tree	Hard
1029	Two City Scheduling	Greedy,Array,Sorting	Medium
1030	Matrix Cells in Distance Order	Geometry,Array,Math,Matrix,Sorting	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays	Array,Dynamic Programming,Sliding Window	Medium
1032	Stream of Characters	Design,Trie,Array,String,Data Stream	Hard
1033	Moving Stones Until Consecutive	Brainteaser,Math	Medium
1034	Coloring A Border	Depth-First Search,Breadth-First Search,Array,Matrix	Medium
1035	Uncrossed Lines	Array,Dynamic Programming	Medium
1036	Escape a Large Maze	Depth-First Search,Breadth-First Search,Array,Hash Table	Hard
1039	Minimum Score Triangulation of Polygon	Array,Dynamic Programming	Medium
1045	Customers Who Bought All Products	Database	Medium	🔒
1046	Last Stone Weight	Array,Heap (Priority Queue)	Easy
1047	Remove All Adjacent Duplicates In String	Stack,String	Easy
1048	Longest String Chain	Array,Hash Table,Two Pointers,String,Dynamic Programming	Medium
1049	Last Stone Weight II	Array,Dynamic Programming	Medium
1050	Actors and Directors Who Cooperated At Least Three Times	Database	Easy	🔒
1051	Height Checker	Array,Counting Sort,Sorting	Easy
1052	Grumpy Bookstore Owner	Array,Sliding Window	Medium
1053	Previous Permutation With One Swap	Greedy,Array	Medium
1054	Distant Barcodes	Greedy,Array,Hash Table,Counting,Sorting,Heap (Priority Queue)	Medium
1055	Shortest Way to Form String	Greedy,String,Dynamic Programming	Medium	🔒
1057	Campus Bikes	Greedy,Array,Sorting	Medium	🔒
1058	Minimize Rounding Error to Meet Target	Greedy,Array,Math,String	Medium	🔒
1059	All Paths from Source Lead to Destination	Depth-First Search,Graph	Medium	🔒
1060	Missing Element in Sorted Array	Array,Binary Search	Medium	🔒
1061	Lexicographically Smallest Equivalent String	Union Find,String	Medium	🔒
1062	Longest Repeating Substring	String,Binary Search,Dynamic Programming,Suffix Array,Hash Function,Rolling Hash	Medium	🔒
1063	Number of Valid Subarrays	Stack,Array,Monotonic Stack	Hard	🔒
1068	Product Sales Analysis I	Database	Easy	🔒
1069	Product Sales Analysis II	Database	Easy	🔒
1070	Product Sales Analysis III	Database	Medium	🔒
1071	Greatest Common Divisor of Strings	Math,String	Easy
1072	Flip Columns For Maximum Number of Equal Rows	Array,Hash Table,Matrix	Medium
1073	Adding Two Negabinary Numbers	Array,Math	Medium
1074	Number of Submatrices That Sum to Target	Array,Hash Table,Matrix,Prefix Sum	Hard
1075	Project Employees I	Database	Easy	🔒
1076	Project Employees II	Database	Easy	🔒
1077	Project Employees III	Database	Medium	🔒
1078	Occurrences After Bigram	String	Easy
1079	Letter Tile Possibilities	String,Backtracking	Medium
1080	Insufficient Nodes in Root to Leaf Paths	Tree,Depth-First Search,Binary Tree	Medium
1081	Smallest Subsequence of Distinct Characters	Stack,Greedy,String,Monotonic Stack	Medium
1085	Sum of Digits in the Minimum Number	Array,Math	Easy	🔒
1090	Largest Values From Labels	Greedy,Array,Hash Table,Counting,Sorting	Medium
1093	Statistics from a Large Sample	Math,Two Pointers,Probability and Statistics	Medium
1094	Car Pooling	Array,Prefix Sum,Sorting,Simulation,Heap (Priority Queue)	Medium
1095	Find in Mountain Array	Array,Binary Search,Interactive	Hard
1096	Brace Expansion II	Stack,Breadth-First Search,String,Backtracking	Hard
1097	Game Play Analysis V	Database	Hard	🔒
1098	Unpopular Books	Database	Medium	🔒
1100	Find K-Length Substrings With No Repeated Characters	Hash Table,String,Sliding Window	Medium	🔒
1101	The Earliest Moment When Everyone Become Friends	Union Find,Array	Medium	🔒
1102	Path With Maximum Minimum Value	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix,Heap (Priority Queue)	Medium	🔒
1103	Distribute Candies to People	Math,Simulation	Easy
1104	Path In Zigzag Labelled Binary Tree	Tree,Math,Binary Tree	Medium
1105	Filling Bookcase Shelves	Array,Dynamic Programming	Medium
1106	Parsing A Boolean Expression	Stack,Recursion,String	Hard
1107	New Users Daily Count	Database	Medium	🔒
1108	Defanging an IP Address	String	Easy
1109	Corporate Flight Bookings	Array,Prefix Sum	Medium
1110	Delete Nodes And Return Forest	Tree,Depth-First Search,Binary Tree	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	Stack,String	Medium
1112	Highest Grade For Each Student	Database	Medium	🔒
1113	Reported Posts	Database	Easy	🔒
1114	Print in Order	Concurrency	Easy
1115	Print FooBar Alternately	Concurrency	Medium
1116	Print Zero Even Odd	Concurrency	Medium
1117	Building H2O	Concurrency	Medium
1118	Number of Days in a Month	Math	Easy	🔒
1119	Remove Vowels from a String	String	Easy	🔒
1120	Maximum Average Subtree	Tree,Depth-First Search,Binary Tree	Medium	🔒
1122	Relative Sort Array	Array,Hash Table,Counting Sort,Sorting	Easy
1123	Lowest Common Ancestor of Deepest Leaves	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium
1124	Longest Well-Performing Interval	Stack,Array,Hash Table,Prefix Sum,Monotonic Stack	Medium
1125	Smallest Sufficient Team	Bit Manipulation,Array,Dynamic Programming,Bitmask	Hard
1126	Active Businesses	Database	Medium	🔒
1127	User Purchase Platform	Database	Hard	🔒
1128	Number of Equivalent Domino Pairs	Array,Hash Table,Counting	Easy
1129	Shortest Path with Alternating Colors	Breadth-First Search,Graph	Medium
1130	Minimum Cost Tree From Leaf Values	Stack,Greedy,Dynamic Programming,Monotonic Stack	Medium
1131	Maximum of Absolute Value Expression	Array,Math	Medium
1132	Reported Posts II	Database	Medium	🔒
1133	Largest Unique Number	Array,Hash Table,Sorting	Easy	🔒
1134	Armstrong Number	Math	Easy	🔒
1135	Connecting Cities With Minimum Cost	Union Find,Graph,Minimum Spanning Tree,Heap (Priority Queue)	Medium	🔒
1136	Parallel Courses	Graph,Topological Sort	Medium	🔒
1137	N-th Tribonacci Number	Memoization,Math,Dynamic Programming	Easy
1138	Alphabet Board Path	Hash Table,String	Medium
1139	Largest 1-Bordered Square	Array,Dynamic Programming,Matrix	Medium
1140	Stone Game II	Array,Math,Dynamic Programming,Game Theory	Medium
1141	User Activity for the Past 30 Days I	Database	Easy	🔒
1148	Article Views I	Database	Easy	🔒
1149	Article Views II	Database	Medium	🔒
1150	Check If a Number Is Majority Element in a Sorted Array	Array,Binary Search	Easy	🔒
1151	Minimum Swaps to Group All 1's Together	Array,Sliding Window	Medium	🔒
1152	Analyze User Website Visit Pattern	Array,Hash Table,Sorting	Medium	🔒
1154	Day of the Year	Math,String	Easy
1155	Number of Dice Rolls With Target Sum	Dynamic Programming	Medium
1156	Swap For Longest Repeated Character Substring	String,Sliding Window	Medium
1157	Online Majority Element In Subarray	Design,Binary Indexed Tree,Segment Tree,Array,Binary Search	Hard
1160	Find Words That Can Be Formed by Characters	Array,Hash Table,String	Easy
1163	Last Substring in Lexicographical Order	Two Pointers,String	Hard
1164	Product Price at a Given Date	Database	Medium	🔒
1167	Minimum Cost to Connect Sticks	Greedy,Array,Heap (Priority Queue)	Medium	🔒
1168	Optimize Water Distribution in a Village	Union Find,Graph,Minimum Spanning Tree	Hard	🔒
1173	Immediate Food Delivery I	Database	Easy	🔒
1174	Immediate Food Delivery II	Database	Medium	🔒
1176	Diet Plan Performance	Array,Sliding Window	Easy	🔒
1177	Can Make Palindrome from Substring	Bit Manipulation,Hash Table,String,Prefix Sum	Medium
1178	Number of Valid Words for Each Puzzle	Bit Manipulation,Trie,Array,Hash Table,String	Hard
1179	Reformat Department Table	Database	Easy
1180	Count Substrings with Only One Distinct Letter	Math,String	Easy	🔒
1181	Before and After Puzzle	Array,Hash Table,String,Sorting	Medium	🔒
1182	Shortest Distance to Target Color	Array,Binary Search,Dynamic Programming	Medium	🔒
1183	Maximum Number of Ones	Greedy,Heap (Priority Queue)	Hard	🔒
1184	Distance Between Bus Stops	Array	Easy
1185	Day of the Week	Math	Easy
1186	Maximum Subarray Sum with One Deletion	Array,Dynamic Programming	Medium
1187	Make Array Strictly Increasing	Array,Binary Search,Dynamic Programming	Hard
1188	Design Bounded Blocking Queue	Concurrency	Medium	🔒
1189	Maximum Number of Balloons	Hash Table,String,Counting	Easy
1190	Reverse Substrings Between Each Pair of Parentheses	Stack,String	Medium
1191	K-Concatenation Maximum Sum	Array,Dynamic Programming	Medium
1192	Critical Connections in a Network	Depth-First Search,Graph,Biconnected Component	Hard
1193	Monthly Transactions I	Database	Medium	🔒
1194	Tournament Winners	Database	Hard	🔒
1195	Fizz Buzz Multithreaded	Concurrency	Medium
1196	How Many Apples Can You Put into the Basket	Greedy,Array,Sorting	Easy	🔒
1197	Minimum Knight Moves	Breadth-First Search	Medium	🔒
1198	Find Smallest Common Element in All Rows	Array,Hash Table,Binary Search,Counting,Matrix	Medium	🔒
1200	Minimum Absolute Difference	Array,Sorting	Easy
1201	Ugly Number III	Math,Binary Search,Number Theory	Medium
1202	Smallest String With Swaps	Depth-First Search,Breadth-First Search,Union Find,Hash Table,String	Medium
1203	Sort Items by Groups Respecting Dependencies	Depth-First Search,Breadth-First Search,Graph,Topological Sort	Hard
1207	Unique Number of Occurrences	Array,Hash Table	Easy
1208	Get Equal Substrings Within Budget	String,Binary Search,Prefix Sum,Sliding Window	Medium
1209	Remove All Adjacent Duplicates in String II	Stack,String	Medium
1210	Minimum Moves to Reach Target with Rotations	Breadth-First Search,Array,Matrix	Hard
1213	Intersection of Three Sorted Arrays	Array,Hash Table,Binary Search,Counting	Easy	🔒
1214	Two Sum BSTs	Stack,Tree,Depth-First Search,Binary Search Tree,Two Pointers,Binary Search,Binary Tree	Medium	🔒
1215	Stepping Numbers	Breadth-First Search,Backtracking	Medium	🔒
1225	Report Contiguous Dates	Database	Hard	🔒
1227	Airplane Seat Assignment Probability	Brainteaser,Math,Dynamic Programming,Probability and Statistics	Medium
1228	Missing Number In Arithmetic Progression	Array,Math	Easy	🔒
1229	Meeting Scheduler	Array,Two Pointers,Sorting	Medium	🔒
1231	Divide Chocolate	Array,Binary Search	Hard	🔒
1237	Find Positive Integer Solution for a Given Equation	Math,Two Pointers,Binary Search,Interactive	Medium
1238	Circular Permutation in Binary Representation	Bit Manipulation,Math,Backtracking	Medium
1239	Maximum Length of a Concatenated String with Unique Characters	Bit Manipulation,Array,String,Backtracking	Medium
1240	Tiling a Rectangle with the Fewest Squares	Dynamic Programming,Backtracking	Hard
1241	Number of Comments per Post	Database	Easy	🔒
1242	Web Crawler Multithreaded	Depth-First Search,Breadth-First Search,Concurrency	Medium	🔒
1246	Palindrome Removal	Array,Dynamic Programming	Hard	🔒
1247	Minimum Swaps to Make Strings Equal	Greedy,Math,String	Medium
1248	Count Number of Nice Subarrays	Array,Hash Table,Math,Sliding Window	Medium
1249	Minimum Remove to Make Valid Parentheses	Stack,String	Medium
1250	Check If It Is a Good Array	Array,Math,Number Theory	Hard
1251	Average Selling Price	Database	Easy	🔒
1252	Cells with Odd Values in a Matrix	Array,Math,Simulation	Easy
1253	Reconstruct a 2-Row Binary Matrix	Greedy,Array,Matrix	Medium
1254	Number of Closed Islands	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Medium
1255	Maximum Score Words Formed by Letters	Bit Manipulation,Array,String,Dynamic Programming,Backtracking,Bitmask	Hard
1256	Encode Number	Bit Manipulation,Math,String	Medium	🔒
1257	Smallest Common Region	Tree,Depth-First Search,Breadth-First Search,Array,Hash Table,String	Medium	🔒
1258	Synonymous Sentences	Union Find,Array,Hash Table,String,Backtracking	Medium	🔒
1259	Handshakes That Don't Cross	Math,Dynamic Programming	Hard	🔒
1260	Shift 2D Grid	Array,Matrix,Simulation	Easy
1261	Find Elements in a Contaminated Binary Tree	Tree,Depth-First Search,Breadth-First Search,Design,Binary Tree	Medium
1262	Greatest Sum Divisible by Three	Greedy,Array,Dynamic Programming	Medium
1263	Minimum Moves to Move a Box to Their Target Location	Breadth-First Search,Array,Matrix,Heap (Priority Queue)	Hard
1271	Hexspeak	Math,String	Easy	🔒
1272	Remove Interval	Array	Medium	🔒
1273	Delete Tree Nodes	Tree,Depth-First Search,Breadth-First Search	Medium	🔒
1274	Number of Ships in a Rectangle	Array,Divide and Conquer,Interactive	Hard	🔒
1279	Traffic Light Controlled Intersection	Concurrency	Easy	🔒
1280	Students and Examinations	Database	Easy	🔒
1282	Group the People Given the Group Size They Belong To	Array,Hash Table	Medium
1283	Find the Smallest Divisor Given a Threshold	Array,Binary Search	Medium
1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix	Bit Manipulation,Breadth-First Search,Array,Matrix	Hard
1285	Find the Start and End Number of Continuous Ranges	Database	Medium	🔒
1286	Iterator for Combination	Design,String,Backtracking,Iterator	Medium
1287	Element Appearing More Than 25% In Sorted Array	Array	Easy
1288	Remove Covered Intervals	Array,Sorting	Medium
1289	Minimum Falling Path Sum II	Array,Dynamic Programming,Matrix	Hard
1290	Convert Binary Number in a Linked List to Integer	Linked List,Math	Easy
1291	Sequential Digits	Enumeration	Medium
1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold	Array,Binary Search,Matrix,Prefix Sum	Medium
1293	Shortest Path in a Grid with Obstacles Elimination	Breadth-First Search,Array,Matrix	Hard
1294	Weather Type in Each Country	Database	Easy	🔒
1295	Find Numbers with Even Number of Digits	Array	Easy
1296	Divide Array in Sets of K Consecutive Numbers	Greedy,Array,Hash Table,Sorting	Medium
1297	Maximum Number of Occurrences of a Substring	Hash Table,String,Sliding Window	Medium
1298	Maximum Candies You Can Get from Boxes	Breadth-First Search,Array	Hard
1299	Replace Elements with Greatest Element on Right Side	Array	Easy
1300	Sum of Mutated Array Closest to Target	Array,Binary Search,Sorting	Medium
1301	Number of Paths with Max Score	Array,Dynamic Programming,Matrix	Hard
1303	Find the Team Size	Database	Easy	🔒
1304	Find N Unique Integers Sum up to Zero	Array,Math	Easy
1305	All Elements in Two Binary Search Trees	Tree,Depth-First Search,Binary Search Tree,Binary Tree,Sorting	Medium
1306	Jump Game III	Depth-First Search,Breadth-First Search,Array	Medium
1307	Verbal Arithmetic Puzzle	Array,Math,String,Backtracking	Hard
1308	Running Total for Different Genders	Database	Medium	🔒
1309	Decrypt String from Alphabet to Integer Mapping	String	Easy
1310	XOR Queries of a Subarray	Bit Manipulation,Array,Prefix Sum	Medium
1311	Get Watched Videos by Your Friends	Breadth-First Search,Array,Hash Table,Sorting	Medium
1312	Minimum Insertion Steps to Make a String Palindrome	String,Dynamic Programming	Hard
1313	Decompress Run-Length Encoded List	Array	Easy
1314	Matrix Block Sum	Array,Matrix,Prefix Sum	Medium
1315	Sum of Nodes with Even-Valued Grandparent	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
1317	Convert Integer to the Sum of Two No-Zero Integers	Math	Easy
1318	Minimum Flips to Make a OR b Equal to c	Bit Manipulation	Medium
1319	Number of Operations to Make Network Connected	Depth-First Search,Breadth-First Search,Union Find,Graph	Medium
1320	Minimum Distance to Type a Word Using Two Fingers	String,Dynamic Programming	Hard
1321	Restaurant Growth	Database	Medium	🔒
1322	Ads Performance	Database	Easy	🔒
1323	Maximum 69 Number	Greedy,Math	Easy
1324	Print Words Vertically	Array,String,Simulation	Medium
1325	Delete Leaves With a Given Value	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium
1326	Minimum Number of Taps to Open to Water a Garden	Greedy,Array,Dynamic Programming	Hard
1330	Reverse Subarray To Maximize Array Value	Greedy,Array,Math	Hard
1331	Rank Transform of an Array	Array,Hash Table,Sorting	Easy
1336	Number of Transactions per Visit	Database	Hard	🔒
1339	Maximum Product of Splitted Binary Tree	Tree,Depth-First Search,Binary Tree	Medium
1340	Jump Game V	Array,Dynamic Programming,Sorting	Hard
1341	Movie Rating	Database	Medium	🔒
1342	Number of Steps to Reduce a Number to Zero	Bit Manipulation,Math	Easy
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	Array,Sliding Window	Medium
1344	Angle Between Hands of a Clock	Math	Medium
1345	Jump Game IV	Breadth-First Search,Array,Hash Table	Hard
1346	Check If N and Its Double Exist	Array,Hash Table,Two Pointers,Binary Search,Sorting	Easy
1347	Minimum Number of Steps to Make Two Strings Anagram	Hash Table,String	Medium
1348	Tweet Counts Per Frequency	Design,Hash Table,Binary Search,Ordered Set,Sorting	Medium
1349	Maximum Students Taking Exam	Bit Manipulation,Array,Dynamic Programming,Bitmask,Matrix	Hard
1350	Students With Invalid Departments	Database	Easy	🔒
1351	Count Negative Numbers in a Sorted Matrix	Array,Binary Search,Matrix	Easy
1352	Product of the Last K Numbers	Design,Queue,Array,Math,Data Stream	Medium
1353	Maximum Number of Events That Can Be Attended	Greedy,Array,Heap (Priority Queue)	Medium
1354	Construct Target Array With Multiple Sums	Array,Heap (Priority Queue)	Hard
1355	Activity Participants	Database	Medium	🔒
1357	Apply Discount Every n Orders	Design,Array,Hash Table	Medium
1364	Number of Trusted Contacts of a Customer	Database	Medium	🔒
1365	How Many Numbers Are Smaller Than the Current Number	Array,Hash Table,Counting,Sorting	Easy
1366	Rank Teams by Votes	Array,Hash Table,String,Counting,Sorting	Medium
1367	Linked List in Binary Tree	Tree,Depth-First Search,Breadth-First Search,Linked List,Binary Tree	Medium
1368	Minimum Cost to Make at Least One Valid Path in a Grid	Breadth-First Search,Graph,Array,Matrix,Shortest Path,Heap (Priority Queue)	Hard
1369	Get the Second Most Recent Activity	Database	Hard	🔒
1370	Increasing Decreasing String	Hash Table,String,Counting	Easy
1371	Find the Longest Substring Containing Vowels in Even Counts	Bit Manipulation,Hash Table,String,Prefix Sum	Medium
1372	Longest ZigZag Path in a Binary Tree	Tree,Depth-First Search,Dynamic Programming,Binary Tree	Medium
1373	Maximum Sum BST in Binary Tree	Tree,Depth-First Search,Binary Search Tree,Dynamic Programming,Binary Tree	Hard
1374	Generate a String With Characters That Have Odd Counts	String	Easy
1375	Bulb Switcher III	Array	Medium
1376	Time Needed to Inform All Employees	Tree,Depth-First Search,Breadth-First Search	Medium
1377	Frog Position After T Seconds	Tree,Depth-First Search,Breadth-First Search,Graph	Hard
1378	Replace Employee ID With The Unique Identifier	Database	Easy	🔒
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
1380	Lucky Numbers in a Matrix	Array,Matrix	Easy
1381	Design a Stack With Increment Operation	Stack,Design,Array	Medium
1382	Balance a Binary Search Tree	Greedy,Tree,Depth-First Search,Binary Search Tree,Divide and Conquer,Binary Tree	Medium
1383	Maximum Performance of a Team	Greedy,Array,Sorting,Heap (Priority Queue)	Hard
1384	Total Sales Amount by Year	Database	Hard	🔒
1385	Find the Distance Value Between Two Arrays	Array,Two Pointers,Binary Search,Sorting	Easy
1386	Cinema Seat Allocation	Greedy,Bit Manipulation,Array,Hash Table	Medium
1387	Sort Integers by The Power Value	Memoization,Dynamic Programming,Sorting	Medium
1388	Pizza With 3n Slices	Greedy,Array,Dynamic Programming,Heap (Priority Queue)	Hard
1389	Create Target Array in the Given Order	Array,Simulation	Easy
1390	Four Divisors	Array,Math	Medium
1391	Check if There is a Valid Path in a Grid	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Medium
1392	Longest Happy Prefix	String,String Matching,Hash Function,Rolling Hash	Hard
1393	Capital GainLoss	Database	Medium	🔒
1394	Find Lucky Integer in an Array	Array,Hash Table,Counting	Easy
1395	Count Number of Teams	Binary Indexed Tree,Array,Dynamic Programming	Medium
1396	Design Underground System	Design,Hash Table,String	Medium
1397	Find All Good Strings	String,Dynamic Programming,String Matching	Hard
1398	Customers Who Bought Products A and B but Not C	Database	Medium	🔒
1399	Count Largest Group	Hash Table,Math	Easy
1400	Construct K Palindrome Strings	Greedy,Hash Table,String,Counting	Medium
1401	Circle and Rectangle Overlapping	Geometry,Math	Medium
1402	Reducing Dishes	Greedy,Array,Dynamic Programming,Sorting	Hard
1403	Minimum Subsequence in Non-Increasing Order	Greedy,Array,Sorting	Easy
1404	Number of Steps to Reduce a Number in Binary Representation to One	Bit Manipulation,String	Medium
1405	Longest Happy String	Greedy,String,Heap (Priority Queue)	Medium
1406	Stone Game III	Array,Math,Dynamic Programming,Game Theory	Hard
1407	Top Travellers	Database	Easy	🔒
1408	String Matching in an Array	String,String Matching	Easy
1409	Queries on a Permutation With Key	Binary Indexed Tree,Array,Simulation	Medium
1410	HTML Entity Parser	Hash Table,String	Medium
1411	Number of Ways to Paint N × 3 Grid	Dynamic Programming	Hard
1412	Find the Quiet Students in All Exams	Database	Hard	🔒
1413	Minimum Value to Get Positive Step by Step Sum	Array,Prefix Sum	Easy
1414	Find the Minimum Number of Fibonacci Numbers Whose Sum Is K	Greedy	Medium
1415	The k-th Lexicographical String of All Happy Strings of Length n	String,Backtracking	Medium
1416	Restore The Array	String,Dynamic Programming	Hard
1417	Reformat The String	String	Easy
1418	Display Table of Food Orders in a Restaurant	Array,Hash Table,String,Ordered Set,Sorting	Medium
1419	Minimum Number of Frogs Croaking	String,Counting	Medium
1420	Build Array Where You Can Find The Maximum Exactly K Comparisons	Dynamic Programming	Hard
1421	NPV Queries	Database	Medium	🔒
1422	Maximum Score After Splitting a String	String	Easy
1423	Maximum Points You Can Obtain from Cards	Array,Prefix Sum,Sliding Window	Medium
1424	Diagonal Traverse II	Array,Sorting,Heap (Priority Queue)	Medium
1425	Constrained Subsequence Sum	Queue,Array,Dynamic Programming,Sliding Window,Monotonic Queue,Heap (Priority Queue)	Hard
1426	Counting Elements	Array,Hash Table	Easy	🔒
1428	Leftmost Column with at Least a One	Array,Binary Search,Interactive,Matrix	Medium	🔒
1429	First Unique Number	Design,Queue,Array,Hash Table,Data Stream	Medium	🔒
1430	Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium	🔒
1431	Kids With the Greatest Number of Candies	Array	Easy
1432	Max Difference You Can Get From Changing an Integer	Greedy,Math	Medium
1433	Check If a String Can Break Another String	Greedy,String,Sorting	Medium
1434	Number of Ways to Wear Different Hats to Each Other	Bit Manipulation,Array,Dynamic Programming,Bitmask	Hard
1436	Destination City	Hash Table,String	Easy
1437	Check If All 1's Are at Least Length K Places Away	Array	Easy
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Queue,Array,Ordered Set,Sliding Window,Monotonic Queue,Heap (Priority Queue)	Medium
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows	Array,Binary Search,Matrix,Heap (Priority Queue)	Hard
1441	Build an Array With Stack Operations	Stack,Array,Simulation	Easy
1442	Count Triplets That Can Form Two Arrays of Equal XOR	Bit Manipulation,Array,Hash Table,Math,Prefix Sum	Medium
1443	Minimum Time to Collect All Apples in a Tree	Tree,Depth-First Search,Breadth-First Search,Hash Table	Medium
1444	Number of Ways of Cutting a Pizza	Memoization,Array,Dynamic Programming,Matrix	Hard
1446	Consecutive Characters	String	Easy
1447	Simplified Fractions	Math	Medium
1448	Count Good Nodes in Binary Tree	Tree,Depth-First Search,Breadth-First Search,Binary Tree	Medium
1449	Form Largest Integer With Digits That Add up to Target	Array,Dynamic Programming	Hard
1474	Delete N Nodes After M Nodes of a Linked List	Linked List	Easy	🔒
1483	Kth Ancestor of a Tree Node	Tree,Depth-First Search,Breadth-First Search,Design,Binary Search,Dynamic Programming	Hard
1490	Clone N-ary Tree	Tree,Depth-First Search,Breadth-First Search,Hash Table	Medium	🔒
1495	Friendly Movies Streamed Last Month	Database	Easy	🔒
1500	Design a File Sharing System	Design,Hash Table,Data Stream,Heap (Priority Queue)	Medium	🔒
1501	Countries You Can Safely Invest In	Database	Medium	🔒
1506	Find Root of N-Ary Tree	Bit Manipulation,Tree,Depth-First Search,Hash Table	Medium	🔒
1507	Reformat Date	String	Easy
1511	Customer Order Frequency	Database	Easy	🔒
1512	Number of Good Pairs	Array,Hash Table,Math,Counting	Easy
1513	Number of Substrings With Only 1s	Math,String	Medium
1515	Best Position for a Service Centre	Geometry,Math,Randomized	Hard
1516	Move Sub-Tree of N-Ary Tree	Tree,Depth-First Search	Hard	🔒
1517	Find Users With Valid E-Mails	Database	Easy	🔒
1518	Water Bottles	Math,Simulation	Easy
1519	Number of Nodes in the Sub-Tree With the Same Label	Tree,Depth-First Search,Breadth-First Search	Medium
1520	Maximum Number of Non-Overlapping Substrings	Greedy,String	Hard
1521	Find a Value of a Mysterious Function Closest to Target	Bit Manipulation,Segment Tree,Array,Binary Search	Hard
1522	Diameter of N-Ary Tree	Tree,Depth-First Search	Medium	🔒
1526	Minimum Number of Increments on Subarrays to Form a Target Array	Stack,Greedy,Array,Dynamic Programming,Monotonic Stack	Hard
1527	Patients With a Condition	Database	Easy	🔒
1528	Shuffle String	Array,String	Easy
1529	Bulb Switcher IV	Greedy,String	Medium
1530	Number of Good Leaf Nodes Pairs	Tree,Depth-First Search,Binary Tree	Medium
1531	String Compression II	String,Dynamic Programming	Hard
1532	The Most Recent Three Orders	Database	Medium	🔒
1533	Find the Index of the Large Integer	Array,Binary Search,Interactive	Medium	🔒
1534	Count Good Triplets	Array,Enumeration	Easy
1535	Find the Winner of an Array Game	Array,Simulation	Medium
1536	Minimum Swaps to Arrange a Binary Grid	Greedy,Array,Matrix	Medium
1537	Get the Maximum Score	Greedy,Array,Two Pointers,Dynamic Programming	Hard
1539	Kth Missing Positive Number	Array,Binary Search	Easy
1540	Can Convert String in K Moves	Hash Table,String	Medium
1541	Minimum Insertions to Balance a Parentheses String	Stack,Greedy,String	Medium
1542	Find Longest Awesome Substring	Bit Manipulation,Hash Table,String	Hard
1544	Make The String Great	Stack,String	Easy
1545	Find Kth Bit in Nth Binary String	Recursion,String	Medium
1546	Maximum Number of Non-Overlapping Subarrays With Sum Equals Target	Greedy,Array,Hash Table,Prefix Sum	Medium
1547	Minimum Cost to Cut a Stick	Array,Dynamic Programming	Hard
1550	Three Consecutive Odds	Array	Easy
1554	Strings Differ by One Character	Hash Table,String,Hash Function,Rolling Hash	Medium	🔒
1555	Bank Account Summary	Database	Medium	🔒
1556	Thousand Separator	String	Easy
1557	Minimum Number of Vertices to Reach All Nodes	Graph	Medium
1558	Minimum Numbers of Function Calls to Make Target Array	Greedy,Array	Medium
1559	Detect Cycles in 2D Grid	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Medium
1564	Put Boxes Into the Warehouse I	Greedy,Array,Sorting	Medium	🔒
1565	Unique Orders and Customers Per Month	Database	Easy	🔒
1568	Minimum Number of Days to Disconnect Island	Depth-First Search,Breadth-First Search,Array,Matrix,Strongly Connected Component	Hard
1569	Number of Ways to Reorder Array to Get Same BST	Tree,Union Find,Binary Search Tree,Memoization,Array,Math,Divide and Conquer,Dynamic Programming,Binary Tree,Combinatorics	Hard
1570	Dot Product of Two Sparse Vectors	Design,Array,Hash Table,Two Pointers	Medium	🔒
1571	Warehouse Manager	Database	Easy	🔒
1576	Replace All 's to Avoid Consecutive Repeating Characters	String	Easy
1577	Number of Ways Where Square of Number Is Equal to Product of Two Numbers	Array,Hash Table,Math,Two Pointers	Medium
1578	Minimum Deletion Cost to Avoid Repeating Letters	Greedy,Array,String,Dynamic Programming	Medium
1579	Remove Max Number of Edges to Keep Graph Fully Traversable	Union Find,Graph	Hard
1580	Put Boxes Into the Warehouse II	Greedy,Array,Sorting	Medium	🔒
1582	Special Positions in a Binary Matrix	Array,Matrix	Easy
1583	Count Unhappy Friends	Array,Simulation	Medium
1584	Min Cost to Connect All Points	Union Find,Array,Minimum Spanning Tree	Medium
1585	Check If String Is Transformable With Substring Sort Operations	Greedy,String,Sorting	Hard
1588	Sum of All Odd Length Subarrays	Array,Math,Prefix Sum	Easy
1589	Maximum Sum Obtained of Any Permutation	Greedy,Array,Prefix Sum,Sorting	Medium
1590	Make Sum Divisible by P	Array,Hash Table,Prefix Sum	Medium
1591	Strange Printer II	Graph,Topological Sort,Array,Matrix	Hard
1592	Rearrange Spaces Between Words	String	Easy
1593	Split a String Into the Max Number of Unique Substrings	Hash Table,String,Backtracking	Medium
1594	Maximum Non Negative Product in a Matrix	Array,Dynamic Programming,Matrix	Medium
1595	Minimum Cost to Connect Two Groups of Points	Bit Manipulation,Array,Dynamic Programming,Bitmask,Matrix	Hard
1598	Crawler Log Folder	Stack,Array,String	Easy
1599	Maximum Profit of Operating a Centennial Wheel	Array,Simulation	Medium
1600	Throne Inheritance	Tree,Depth-First Search,Design,Hash Table	Medium
1601	Maximum Number of Achievable Transfer Requests	Bit Manipulation,Enumeration	Hard
1603	Design Parking System	Design,Counting,Simulation	Easy
1604	Alert Using Same Key-Card Three or More Times in a One Hour Period	Array,Hash Table,String,Sorting	Medium
1605	Find Valid Matrix Given Row and Column Sums	Greedy,Array,Matrix	Medium
1606	Find Servers That Handled Most Number of Requests	Greedy,Array,Ordered Set,Heap (Priority Queue)	Hard
1614	Maximum Nesting Depth of the Parentheses	Stack,String	Easy
1618	Maximum Font to Fit a Sentence in a Screen	Array,String,Binary Search,Interactive	Medium	🔒
1619	Mean of Array After Removing Some Elements	Array,Sorting	Easy
1627	Graph Connectivity With Threshold	Union Find,Array,Math	Hard
1632	Rank Transform of a Matrix	Greedy,Union Find,Graph,Topological Sort,Array,Matrix	Hard
1640	Check Array Formation Through Concatenation	Array,Hash Table	Easy
1651	Hopper Company Queries III	Database	Hard	🔒
1660	Correct a Binary Tree	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium	🔒
1661	Average Time of Process per Machine	Database	Easy	🔒
1662	Check If Two String Arrays are Equivalent	Array,String	Easy
1666	Change the Root of a Binary Tree	Tree,Depth-First Search,Binary Tree	Medium	🔒
1667	Fix Names in a Table	Database	Easy	🔒
1676	Lowest Common Ancestor of a Binary Tree IV	Tree,Depth-First Search,Binary Tree	Medium	🔒
1677	Product's Worth Over Invoices	Database	Easy	🔒
1678	Goal Parser Interpretation	String	Easy
1679	Max Number of K-Sum Pairs	Array,Hash Table,Two Pointers,Sorting	Medium
1680	Concatenation of Consecutive Binary Numbers	Bit Manipulation,Math,Simulation	Medium
1681	Minimum Incompatibility	Bit Manipulation,Array,Dynamic Programming,Bitmask	Hard
1682	Longest Palindromic Subsequence II	String,Dynamic Programming	Medium	🔒
1688	Count of Matches in Tournament	Math,Simulation	Easy
1689	Partitioning Into Minimum Number Of Deci-Binary Numbers	Greedy,String	Medium
1690	Stone Game VII	Array,Math,Dynamic Programming,Game Theory	Medium
1691	Maximum Height by Stacking Cuboids	Array,Dynamic Programming,Sorting	Hard
1693	Daily Leads and Partners	Database	Easy	🔒
1694	Reformat Phone Number	String	Easy
1695	Maximum Erasure Value	Array,Hash Table,Sliding Window	Medium
1696	Jump Game VI	Queue,Array,Dynamic Programming,Sliding Window,Monotonic Queue,Heap (Priority Queue)	Medium
1697	Checking Existence of Edge Length Limited Paths	Union Find,Graph,Array,Sorting	Hard
1698	Number of Distinct Substrings in a String	Trie,String,Suffix Array,Hash Function,Rolling Hash	Medium	🔒
1699	Number of Calls Between Two Persons	Database	Medium	🔒
1700	Number of Students Unable to Eat Lunch	Stack,Queue,Array,Simulation	Easy
1701	Average Waiting Time	Array,Simulation	Medium
1702	Maximum Binary String After Change	Greedy,String	Medium
1703	Minimum Adjacent Swaps for K Consecutive Ones	Greedy,Array,Prefix Sum,Sliding Window	Hard
1704	Determine if String Halves Are Alike	String,Counting	Easy
1705	Maximum Number of Eaten Apples	Greedy,Array,Heap (Priority Queue)	Medium
1707	Maximum XOR With an Element From Array	Bit Manipulation,Trie,Array	Hard
1708	Largest Subarray Length K	Greedy,Array	Easy	🔒
1709	Biggest Window Between Visits	Database	Medium	🔒
1714	Sum Of Special Evenly-Spaced Elements In Array	Array,Dynamic Programming	Hard	🔒
1715	Count Apples and Oranges	Database	Medium	🔒
1716	Calculate Money in Leetcode Bank	Math	Easy
1717	Maximum Score From Removing Substrings	Stack,Greedy,String	Medium
1718	Construct the Lexicographically Largest Valid Sequence	Array,Backtracking	Medium
1719	Number Of Ways To Reconstruct A Tree	Tree,Graph,Topological Sort	Hard
1720	Decode XORed Array	Bit Manipulation,Array	Easy
1721	Swapping Nodes in a Linked List	Linked List,Two Pointers	Medium
1722	Minimize Hamming Distance After Swap Operations	Depth-First Search,Union Find,Array	Medium
1724	Checking Existence of Edge Length Limited Paths II	Union Find,Graph,Minimum Spanning Tree	Hard	🔒
1725	Number Of Rectangles That Can Form The Largest Square	Array	Easy
1726	Tuple with Same Product	Array,Hash Table	Medium
1727	Largest Submatrix With Rearrangements	Greedy,Array,Matrix,Sorting	Medium
1729	Find Followers Count	Database	Easy	🔒
1730	Shortest Path to Get Food	Breadth-First Search,Array,Matrix	Medium	🔒
1731	The Number of Employees Which Report to Each Employee	Database	Easy	🔒
1733	Minimum Number of People to Teach	Greedy,Array	Medium
1734	Decode XORed Permutation	Bit Manipulation,Array	Medium
1735	Count Ways to Make Array With Product	Array,Math,Dynamic Programming	Hard
1736	Latest Time by Replacing Hidden Digits	String	Easy
1737	Change Minimum Characters to Satisfy One of Three Conditions	Hash Table,String,Counting,Prefix Sum	Medium
1738	Find Kth Largest XOR Coordinate Value	Bit Manipulation,Array,Divide and Conquer,Matrix,Prefix Sum,Quickselect,Heap (Priority Queue)	Medium
1739	Building Boxes	Greedy,Math,Binary Search	Hard
1740	Find Distance in a Binary Tree	Tree,Depth-First Search,Breadth-First Search,Hash Table,Binary Tree	Medium	🔒
1742	Maximum Number of Balls in a Box	Hash Table,Math,Counting	Easy
1743	Restore the Array From Adjacent Pairs	Array,Hash Table	Medium
1744	Can You Eat Your Favorite Candy on Your Favorite Day	Array,Prefix Sum	Medium
1745	Palindrome Partitioning IV	String,Dynamic Programming	Hard
1747	Leetflex Banned Accounts	Database	Medium	🔒
1748	Sum of Unique Elements	Array,Hash Table,Counting	Easy
1749	Maximum Absolute Sum of Any Subarray	Array,Dynamic Programming	Medium
1750	Minimum Length of String After Deleting Similar Ends	Two Pointers,String	Medium
1751	Maximum Number of Events That Can Be Attended II	Array,Binary Search,Dynamic Programming	Hard
1752	Check if Array Is Sorted and Rotated	Array	Easy
1753	Maximum Score From Removing Stones	Greedy,Math,Heap (Priority Queue)	Medium
1754	Largest Merge Of Two Strings	Greedy,Two Pointers,String	Medium
1755	Closest Subsequence Sum	Bit Manipulation,Array,Two Pointers,Dynamic Programming,Bitmask	Hard
1756	Design Most Recently Used Queue	Stack,Design,Binary Indexed Tree,Array,Hash Table,Ordered Set	Medium	🔒
1757	Recyclable and Low Fat Products	Database	Easy	🔒
1758	Minimum Changes To Make Alternating Binary String	String	Easy
1759	Count Number of Homogenous Substrings	Math,String	Medium
1760	Minimum Limit of Balls in a Bag	Array,Binary Search	Medium
1761	Minimum Degree of a Connected Trio in a Graph	Graph	Hard
1762	Buildings With an Ocean View	Stack,Array,Monotonic Stack	Medium	🔒
1763	Longest Nice Substring	Bit Manipulation,Hash Table,String,Sliding Window	Easy
1764	Form Array by Concatenating Subarrays of Another Array	Greedy,Array,String Matching	Medium
1765	Map of Highest Peak	Breadth-First Search,Array,Matrix	Medium
1766	Tree of Coprimes	Tree,Depth-First Search,Breadth-First Search,Math	Hard
1767	Find the Subtasks That Did Not Execute	Database	Hard	🔒
1769	Minimum Number of Operations to Move All Balls to Each Box	Array,String	Medium
1772	Sort Features by Popularity	Array,Hash Table,String,Sorting	Medium	🔒
1773	Count Items Matching a Rule	Array,String	Easy
1774	Closest Dessert Cost	Array,Dynamic Programming,Backtracking	Medium
1775	Equal Sum Arrays With Minimum Number of Operations	Greedy,Array,Hash Table,Counting	Medium
1776	Car Fleet II	Stack,Array,Math,Monotonic Stack,Heap (Priority Queue)	Hard
1777	Product's Price for Each Store	Database	Easy	🔒
1778	Shortest Path in a Hidden Grid	Depth-First Search,Breadth-First Search,Graph,Interactive	Medium	🔒
1783	Grand Slam Titles	Database	Medium	🔒
1784	Check if Binary String Has at Most One Segment of Ones	String	Easy
1785	Minimum Elements to Add to Form a Given Sum	Greedy,Array	Medium
1786	Number of Restricted Paths From First to Last Node	Graph,Topological Sort,Dynamic Programming,Shortest Path,Heap (Priority Queue)	Medium
1787	Make the XOR of All Segments Equal to Zero	Bit Manipulation,Array,Dynamic Programming	Hard
1788	Maximize the Beauty of the Garden	Greedy,Array,Prefix Sum	Hard	🔒
1790	Check if One String Swap Can Make Strings Equal	Hash Table,String,Counting	Easy
1791	Find Center of Star Graph	Graph	Easy
1792	Maximum Average Pass Ratio	Greedy,Array,Heap (Priority Queue)	Medium
1793	Maximum Score of a Good Subarray	Stack,Array,Two Pointers,Binary Search,Monotonic Stack	Hard
1796	Second Largest Digit in a String	Hash Table,String	Easy
1797	Design Authentication Manager	Design,Hash Table	Medium
1798	Maximum Number of Consecutive Values You Can Make	Greedy,Array	Medium
1799	Maximize Score After N Operations	Bit Manipulation,Array,Math,Dynamic Programming,Backtracking,Bitmask,Number Theory	Hard
1800	Maximum Ascending Subarray Sum	Array	Easy
1801	Number of Orders in the Backlog	Array,Simulation,Heap (Priority Queue)	Medium
1802	Maximum Value at a Given Index in a Bounded Array	Greedy,Binary Search	Medium
1803	Count Pairs With XOR in a Range	Bit Manipulation,Trie,Array	Hard
1805	Number of Different Integers in a String	Hash Table,String	Easy
1806	Minimum Number of Operations to Reinitialize a Permutation	Array,Math,Simulation	Medium
1807	Evaluate the Bracket Pairs of a String	Array,Hash Table,String	Medium
1808	Maximize Number of Nice Divisors	Recursion,Math	Hard
1812	Determine Color of a Chessboard Square	Math,String	Easy
1813	Sentence Similarity III	Array,Two Pointers,String	Medium
1814	Count Nice Pairs in an Array	Array,Hash Table,Math,Counting	Medium
1815	Maximum Number of Groups Getting Fresh Donuts	Bit Manipulation,Memoization,Array,Dynamic Programming,Bitmask	Hard
1827	Minimum Operations to Make the Array Increasing	Greedy,Array	Easy
1828	Queries on Number of Points Inside a Circle	Geometry,Array,Math	Medium
1830	Minimum Number of Operations to Make String Sorted	Math,String,Combinatorics	Hard
1839	Longest Substring Of All Vowels in Order	String,Sliding Window	Medium
1852	Distinct Numbers in Each Subarray	Array,Hash Table,Sliding Window	Medium	🔒
1853	Convert Date Format	Database	Easy	🔒
1858	Longest Word With All Prefixes	Depth-First Search,Trie	Medium	🔒
1867	Orders With Maximum Quantity Above Average	Database	Medium	🔒
1868	Product of Two Run-Length Encoded Arrays	Array,Two Pointers	Medium	🔒
1871	Jump Game VII	Two Pointers,String,Prefix Sum	Medium
1872	Stone Game VIII	Array,Math,Dynamic Programming,Game Theory,Prefix Sum	Hard
1873	Calculate Special Bonus	Database	Easy	🔒
1874	Minimize Product Sum of Two Arrays	Greedy,Array,Sorting	Medium	🔒
1875	Group Employees of the Same Salary	Database	Medium	🔒
1880	Check if Word Equals Summation of Two Words	String	Easy
1881	Maximum Value after Insertion	Greedy,String	Medium
1882	Process Tasks Using Servers	Array,Heap (Priority Queue)	Medium
1883	Minimum Skips to Arrive at Meeting On Time	Array,Dynamic Programming	Hard
1884	Egg Drop With 2 Eggs and N Floors	Math,Dynamic Programming	Medium
1885	Count Pairs in Two Arrays	Array,Binary Search,Sorting	Medium	🔒
1886	Determine Whether Matrix Can Be Obtained By Rotation	Array,Matrix	Easy
1887	Reduction Operations to Make the Array Elements Equal	Array,Sorting	Medium
1888	Minimum Number of Flips to Make the Binary String Alternating	Greedy,String	Medium
1889	Minimum Space Wasted From Packaging	Array,Binary Search,Prefix Sum,Sorting	Hard
1890	The Latest Login in 2020	Database	Easy	🔒
1891	Cutting Ribbons	Array,Binary Search	Medium	🔒
1892	Page Recommendations II	Database	Hard	🔒
1893	Check if All the Integers in a Range Are Covered	Array,Hash Table,Prefix Sum	Easy
1894	Find the Student that Will Replace the Chalk	Array,Binary Search,Prefix Sum,Simulation	Medium
1895	Largest Magic Square	Array,Matrix,Prefix Sum	Medium
1896	Minimum Cost to Change the Final Value of Expression	Stack,Math,String,Dynamic Programming	Hard
1897	Redistribute Characters to Make All Strings Equal	Hash Table,String,Counting	Easy
1898	Maximum Number of Removable Characters	Array,String,Binary Search	Medium
1899	Merge Triplets to Form Target Triplet	Greedy,Array	Medium
1900	The Earliest and Latest Rounds Where Players Compete	Memoization,Dynamic Programming	Hard
1901	Find a Peak Element II	Array,Binary Search,Divide and Conquer,Matrix	Medium
1902	Depth of BST Given Insertion Order	Tree,Binary Search Tree,Binary Tree,Ordered Set	Medium	🔒
1903	Largest Odd Number in String	Greedy,Math,String	Easy
1904	The Number of Full Rounds You Have Played	Math,String	Medium
1905	Count Sub Islands	Depth-First Search,Breadth-First Search,Union Find,Array,Matrix	Medium
1906	Minimum Absolute Difference Queries	Array,Hash Table	Medium
1907	Count Salary Categories	Database	Medium	🔒
1908	Game of Nim	Bit Manipulation,Brainteaser,Array,Math,Dynamic Programming,Game Theory	Medium	🔒
1909	Remove One Element to Make the Array Strictly Increasing	Array	Easy
1910	Remove All Occurrences of a Substring	String	Medium
1911	Maximum Alternating Subsequence Sum	Array,Dynamic Programming	Medium
1912	Design Movie Rental System	Design,Array,Hash Table,Ordered Set,Heap (Priority Queue)	Hard
1913	Maximum Product Difference Between Two Pairs	Array,Sorting	Easy
1914	Cyclically Rotating a Grid	Array,Matrix,Simulation	Medium
1915	Number of Wonderful Substrings	Bit Manipulation,Hash Table,String,Prefix Sum	Medium
1916	Count Ways to Build Rooms in an Ant Colony	Tree,Graph,Topological Sort,Math,Dynamic Programming,Combinatorics	Hard
1917	Leetcodify Friends Recommendations	Database	Hard	🔒
1918	Kth Smallest Subarray Sum	Array,Binary Search,Sliding Window	Medium	🔒
1919	Leetcodify Similar Friends		Hard	🔒
1920	Build Array from Permutation	Array,Simulation	Easy
1921	Eliminate Maximum Number of Monsters	Greedy,Array,Sorting	Medium
1922	Count Good Numbers	Recursion,Math	Medium
1923	Longest Common Subpath	Array,Binary Search,Suffix Array,Hash Function,Rolling Hash	Hard
1924	Erect the Fence II	Geometry,Array,Math	Hard	🔒
1925	Count Square Sum Triples	Math,Enumeration	Easy
1926	Nearest Exit from Entrance in Maze	Breadth-First Search,Array,Matrix	Medium
1927	Sum Game	Greedy,Math,Game Theory	Medium
1928	Minimum Cost to Reach Destination in Time	Graph,Dynamic Programming	Hard
1929	Concatenation of Array	Array	Easy
1930	Unique Length-3 Palindromic Subsequences	Hash Table,String,Prefix Sum	Medium
1931	Painting a Grid With Three Different Colors	Dynamic Programming	Hard
1932	Merge BSTs to Create Single BST	Tree,Depth-First Search,Hash Table,Binary Search,Binary Tree	Hard
1933	Check if String Is Decomposable Into Value-Equal Substrings	String	Easy	🔒
1934	Confirmation Rate		Medium	🔒
1935	Maximum Number of Words You Can Type	Hash Table,String	Easy
1936	Add Minimum Number of Rungs		Medium
1937	Maximum Number of Points with Cost		Medium
1938	Maximum Genetic Difference Query		Hard
1939	Users That Actively Request Confirmation Messages		Easy	🔒
1940	Longest Common Subsequence Between Sorted Arrays	Array,Hash Table,Counting	Medium	🔒
1941	Check if All Characters Have Equal Number of Occurrences	Hash Table,String,Counting	Easy
1942	The Number of the Smallest Unoccupied Chair	Array,Ordered Set,Heap (Priority Queue)	Medium
1943	Describe the Painting	Array,Prefix Sum	Medium
1944	Number of Visible People in a Queue	Stack,Array,Monotonic Stack	Hard
1945	Sum of Digits of String After Convert	String,Simulation	Easy
1946	Largest Number After Mutating Substring	Greedy,Array,String	Medium
1947	Maximum Compatibility Score Sum	Bit Manipulation,Array,Dynamic Programming,Backtracking,Bitmask	Medium
1948	Delete Duplicate Folders in System	Trie,Array,Hash Table,String,Hash Function	Hard
1949	Strong Friendship		Medium	🔒
1950	Maximum of Minimum Values in All Subarrays		Medium	🔒
1951	All the Pairs With the Maximum Number of Common Followers		Medium	🔒
1952	Three Divisors	Math	Easy
1953	Maximum Number of Weeks for Which You Can Work	Greedy,Array	Medium
1954	Minimum Garden Perimeter to Collect Enough Apples	Math,Binary Search	Medium
1955	Count Number of Special Subsequences	Array,Dynamic Programming	Hard
1956	Minimum Time For K Virus Variants to Spread	Geometry,Array,Math,Binary Search,Enumeration	Hard	🔒
1957	Delete Characters to Make Fancy String	String	Easy
1958	Check if Move is Legal	Array,Enumeration,Matrix	Medium
1959	Minimum Total Space Wasted With K Resizing Operations	Array,Dynamic Programming	Medium
1961	Check If String Is a Prefix of Array	Array,String	Easy
1962	Remove Stones to Minimize the Total	Array,Heap (Priority Queue)	Medium
1963	Minimum Number of Swaps to Make the String Balanced	Stack,Greedy,Two Pointers,String	Medium
1964	Find the Longest Valid Obstacle Course at Each Position	Binary Indexed Tree,Array,Binary Search	Hard
1965	Employees With Missing Information		Easy	🔒
1966	Binary Searchable Numbers in an Unsorted Array		Medium	🔒
1967	Number of Strings That Appear as Substrings in Word	String	Easy
1968	Array With Elements Not Equal to Average of Neighbors	Greedy,Array,Sorting	Medium
1969	Minimum Non-Zero Product of the Array Elements	Greedy,Recursion,Math	Medium
1970	Last Day Where You Can Still Cross	Depth-First Search,Breadth-First Search,Union Find,Array,Binary Search,Matrix	Hard
1971	Find if Path Exists in Graph	Depth-First Search,Breadth-First Search,Graph	Easy
1972	First and Last Call On the Same Day		Hard	🔒
1973	Count Nodes Equal to Sum of Descendants		Medium	🔒
1974	Minimum Time to Type Word Using Special Typewriter	Greedy,String	Easy
1975	Maximum Matrix Sum	Greedy,Array,Matrix	Medium
1976	Number of Ways to Arrive at Destination	Graph,Topological Sort,Dynamic Programming,Shortest Path	Medium
1977	Number of Ways to Separate Numbers	String,Dynamic Programming,Suffix Array	Hard
1978	Employees Whose Manager Left the Company		Easy	🔒
1979	Find Greatest Common Divisor of Array	Array,Math	Easy
1980	Find Unique Binary String	Array,String,Backtracking	Medium
1981	Minimize the Difference Between Target and Chosen Elements	Array,Dynamic Programming,Matrix	Medium
1982	Find Array Given Subset Sums	Array,Divide and Conquer	Hard
1983	Widest Pair of Indices With Equal Range Sum		Medium	🔒
1984	Minimum Difference Between Highest and Lowest of K Scores	Array,Sorting	Easy
1985	Find the Kth Largest Integer in the Array	Array,String,Divide and Conquer,Quickselect,Sorting,Heap (Priority Queue)	Medium
1986	Minimum Number of Work Sessions to Finish the Tasks	Bit Manipulation,Array,Dynamic Programming,Backtracking,Bitmask	Medium
1987	Number of Unique Good Subsequences	String,Dynamic Programming	Hard
1988	Find Cutoff Score for Each School		Medium	🔒
1990	Count the Number of Experiments		Easy	🔒
1991	Find the Middle Index in Array	Array,Prefix Sum	Easy
1992	Find All Groups of Farmland	Depth-First Search,Breadth-First Search,Array,Matrix	Medium
1993	Operations on Tree	Tree,Breadth-First Search,Design,Hash Table	Medium
1994	The Number of Good Subsets	Bit Manipulation,Array,Math,Dynamic Programming,Bitmask	Hard
1995	Count Special Quadruplets	Array,Enumeration	Easy
1996	The Number of Weak Characters in the Game	Stack,Greedy,Array,Sorting,Monotonic Stack	Medium
1997	First Day Where You Have Been in All the Rooms	Array,Dynamic Programming	Medium
1998	GCD Sort of an Array	Union Find,Array,Math,Sorting	Hard
1999	Smallest Greater Multiple Made of Two Digits		Medium	🔒
2000	Reverse Prefix of Word	Two Pointers,String	Easy
2001	Number of Pairs of Interchangeable Rectangles	Array,Hash Table,Math,Counting,Number Theory	Medium
2002	Maximum Product of the Length of Two Palindromic Subsequences	Bit Manipulation,String,Dynamic Programming,Backtracking,Bitmask	Medium
2003	Smallest Missing Genetic Value in Each Subtree	Tree,Depth-First Search,Union Find,Dynamic Programming	Hard
2004	The Number of Seniors and Juniors to Join the Company		Hard	🔒
2005	Subtree Removal Game with Fibonacci Tree		Hard	🔒
2006	Count Number of Pairs With Absolute Difference K	Array	Easy
2007	Find Original Array From Doubled Array	Greedy,Array,Hash Table,Sorting	Medium
2008	Maximum Earnings From Taxi	Array,Binary Search,Dynamic Programming,Sorting	Medium
2009	Minimum Number of Operations to Make Array Continuous	Array,Binary Search	Hard
2010	The Number of Seniors and Juniors to Join the Company II		Hard	🔒
2011	Final Value of Variable After Performing Operations	Array,String,Simulation	Easy
2012	Sum of Beauty in the Array	Array	Medium
2013	Detect Squares	Design,Array,Hash Table,Counting	Medium
2014	Longest Subsequence Repeated k Times	Greedy,String,Backtracking,Counting,Enumeration	Hard
2015	Average Height of Buildings in Each Segment		Medium	🔒
2016	Maximum Difference Between Increasing Elements		Easy
2017	Grid Game		Medium
2018	Check if Word Can Be Placed In Crossword		Medium
2019	The Score of Students Solving Math Expression		Hard

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