| # | Solution | Tag | Difficulty | Remark |
|---|---|---|---|---|
| 0001 | Two Sum | Array, Hash Table |  |
|
| 0002 | Add Two Numbers | Linked List, Math, Recursion |  |
|
| 0004 | Median of Two Sorted Arrays | Array, Binary Search, Divide & Conquer |  |
|
| 0007 | Reverse Integer | Math | |
|
| 0009 | Palindrome Number | Math | |
|
| 0013 | Roman to Integer | String, Math, Hash Table | |
|
| 0014 | Longest Common Prefix | String | |
|
| 0020 | Valid Parentheses | String, ST | |
|
| 0021 | Merge Two Sorted Lists | LL, Recursion | |
|
| 0022 | Generate Parentheses | String, DP, Backtracking | |
|
| 0024 | Swap Nodes in Pairs | Linked List, Recursion | |
|
| 0026 | Remove Duplicates | Array, Two Pointers | |
|
| 0027 | Remove Element | Array, Two Pointers | |
|
| 0028 | Find the Index of the First Occurrence in a String | 2P, String, String Matching | |
|
| 0035 | Search Insert Position | Array, BS | |
|
| 0037 | Sudoku Solver | Array, Backtracking, Matrix | |
|
| 0041 | First Missing Positive | Array, Hash Table | |
|
| 0042 | Trapping Rain Water | Array, 2P, DP, ST, Monotonic Stack | |
|
| 0048 | Rotate Image | Array, Math, Matrix | |
|
| 0051 | N-Queens | Array, Backtracking | |
|
| 0053 | Maximum Subarray | Array, DNC, DP | |
|
| 0055 | Jump Game | Array, DP, Greedy | |
|
| 0058 | Length of Last Word | String | |
|
| 0061 | Rotate List | Linked List, Two Pointers | |
|
| 0066 | Plus One | Array, Math | |
|
| 0067 | Add Binary | Math, String, Bit Manip, Simulation | |
|
| 0069 | Sqrt(x) | Math, BS | |
|
| 0070 | Climbing Stairs | Math, DP, Memorization | |
|
| 0072 | Edit Distance | String, DP | |
|
| 0074 | Search a 2D Matrix | Array, BS, Matrix | |
|
| 0075 | Sort Colors | Array, Two Pointers, Sorting | |
|
| 0078 | Subsets | Array, Backtracking, Bit Manip | |
|
| 0083 | Remove Duplicates from Sorted List | LL | |
|
| 0088 | Merge Sorted Array | Array, 2P, Sorting | |
|
| 0094 | Binary Tree Inorder Traversal | Tree, Stack, DFS, Binary Tree | |
|
| 0098 | Validate BST | Tree, DFS, BST, Binary Tree | |
|
| 0100 | Same Tree | Tree, DFS, BFS, Binary Tree | |
|
| 0101 | Symmetric Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | |
|
| 0103 | Binary Tree Zigzag Level Order Traversal | Tree, BFS, Binary Tree | |
|
| 0104 | Maximum Depth of Binary Tree | Tree, BFS, DFS, Binary Tree | |
|
| 0106 | Construct Binary Tree from Inorder and Postorder Traversal | Array, Hash Table, DNC, Tree, Binary Tree | |
|
| 0108 | Convert Sorted Array to Binary Search Tree | Array, DNC, Tree, BST, Binary Tree | |
|
| 0109 | Convert Sorted List to Binary Search Tree | LL, DNC, Tree, BST, Binary Tree | |
|
| 0110 | Balanced Binary Tree | Tree, DFS, Binary Tree | |
|
| 0111 | Minimum Depth of Binary Tree | Tree, DFS, BFS, Binary Tree | |
|
| 0112 | Path Sum | Tree, Depth-First Search, Breadth-First Search, Binary Tree | |
|
| 0118 | Pascal's Triangle | Array, DP | |
|
| 0119 | Pascal's Triangle II | Array, DP | |
|
| 0121 | Best Time to Buy and Sell Stock | Array, DP | |
|
| 0122 | Best Time to Buy and Sell Stock II | Array, DP, Greedy | |
|
| 0125 | Valid Palindrome | 2P, String | |
|
| 0129 | Sum Root to Leaf Numbers | Tree, Depth-First Search, Binary Tree | |
|
| 0136 | Single Number | Array, Bit Manip | |
|
| 0141 | Linked List Cycle | Hash Table, LL, 2P | |
|
| 0142 | Linked List Cycle II | Hash Table, LL, 2P | |
|
| 0144 | Binary Tree Preorder Traversal | Stack, Tree, DFS, Binary Tree | |
|
| 0145 | Binary Tree Postorder Traversal | Stack, Tree, DFS, Binary Tree | |
|
| 0160 | Intersection of Two Linked Lists | Hash Table, LL, 2P | |
|
| 0169 | Majority Element | Array, Hash Table, DNC, Sorting, Counting | |
|
| 0172 | Factorial Trailing Zeroes | Math | |
|
| 0190 | Reverse Bits | DNC, Bit Manip | |
|
| 0191 | Number of 1 Bits | Divide & Conquer, Bit Manipulation | |
|
| 0193 | Valid Phone Numbers | Shell | |
|
| 0195 | Tenth Line | Shell | |
|
| 0199 | Binary Tree Right Side View | Tree, DFS, BFS, Binary Tree | |
|
| 0200 | Number of Islands | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | |
|
| 0202 | Happy Number | Hash Table, Math, 2P | |
|
| 0203 | Remove Linked List Elements | LL, Recursion | |
|
| 0205 | Isomorphic Strings | Hash Table, String | |
|
| 0206 | Reverse Linked List | Linked List, Recursion | |
|
| 0211 | Design Add and Search Words Data Structure | String, Depth-First Search, Design, Trie | |
|
| 0217 | Contains Duplicate | Array, Hash Table, Sorting | |
|
| 0219 | Contains Duplicate II | Array, Hash Table, Sliding Window | |
|
| 0222 | Count Complete Tree Nodes | Binary Search, Tree, DFS, Binary Tree | |
|
| 0225 | Implement Stack using Queues | ST, Design, Q | |
|
| 0226 | Invert Binary Tree | Tree, Depth-First Search, Breadth-First Search, Binary Tree | |
|
| 0228 | Summary Ranges | Array | |
|
| 0230 | Kth Smallest Element in a BST | Tree, DFS, BST, Binary Tree | |
|
| 0231 | Power of Two | Math, Bit Manipulation, Recursion | |
|
| 0232 | Implement Queue using Stacks | ST, Design, Q | |
|
| 0234 | Palindrome Linked List | LL, 2P, ST, Recursion | |
|
| 0236 | Lowest Common Ancestor of a Binary Tree | Tree, Depth-First Search, Binary Tree | |
|
| 0242 | Valid Anagram | Hash Table, String, Sorting | |
|
| 0257 | Binary Tree Paths | String, Backtracking, Tree, Depth-First Search, Binary Tree | |
|
| 0258 | Add Digits | Math, Simulation, Number Theory | |
|
| 0263 | Ugly Number | Math | |
|
| 0268 | Missing Number | Array, Hash Table, Math, BS, Bit Manip, Sorting | |
|
| 0278 | First Bad Version | Binary Search, Interactive | |
|
| 0279 | Perfect Squares | Math, DP, Breadth-First Search | |
|
| 0283 | Move Zeroes | Array, Two Pointers | |
|
| 0290 | Word Pattern | Hash Table, String | |
|
| 0292 | Nim Game | Math, Brainteaser, Game Theory | |
|
| 0300 | Longest Increasing Subsequence | Array, Binary Search, DP | |
|
| 0322 | Coin Change | Array, DP, BFS | |
|
| 0326 | Power of Three | Math, Recursion | |
|
| 0337 | House Robber III | DP, Tree, DFS, Binary Tree | |
|
| 0338 | Counting Bits | DP, Bit Manip | |
|
| 0342 | Power of Four | Math, Bit Manip, Recursion | |
|
| 0344 | Reverse String | Two Pointers, String, Recursion | |
|
| 0345 | Reverse Vowels of a String | 2P, String | |
|
| 0349 | Intersection of Two Arrays | Array, Hash Table, 2P, BS, Sorting | |
|
| 0350 | Intersection of Two Arrays II | Array, Hash Table, 2P, BS, Sorting | |
|
| 0367 | Valid Perfect Square | Math, Binary Search | |
|
| 0369 | Plus One Linked List | Linked List, Math | |
🔒 |
| 0374 | Guess Number Higher or Lower | BS, Interactive | |
|
| 0382 | Linked List Random Node | LL, Math, Reservoir Sampling, Randomized | |
|
| 0383 | Ransom Note | Hash Table, String, Counting | |
|
| 0387 | First Unique Character in a String | Hash Table, String, Q, Counting | |
|
| 0389 | Find the Difference | Hash Table, String, Bit Manipulation, Sorting | |
|
| 0392 | Is Subsequence | 2P, String, DP | |
|
| 0401 | Binary Watch | Backtracking, Bit Manip | |
|
| 0404 | Sum of Left Leaves | Tree, Depth-First Search, Breadth-First Search, Binary Tree | |
|
| 0412 | Fizz Buzz | Math, String, Simulation | |
|
| 0414 | Third Maximum Number | Array, Sorting | |
|
| 0434 | Number of Segments in a String | String | |
|
| 0438 | Find All Anagrams in a String | Hash Table, String, Sliding Window | |
|
| 0441 | Arranging Coins | Math, BS | |
|
| 0442 | Find All Duplicates | Array, Hash Table | |
|
| 0443 | String Compression | 2P, String | |
|
| 0445 | Add Two Numbers II | Linked List, Math, Stack | |
|
| 0448 | Find All Numbers Disappeared in an Array | Array, Hash Table | |
|
| 0461 | Hamming Distance | Bit Manip | |
|
| 0463 | Island Perimeter | Array, Depth-First Search, Breadth-First Search, Matrix | |
|
| 0476 | Number Complement | Bit Manip | |
|
| 0482 | License Key Formatting | String | |
|
| 0485 | Max Consecutive Ones | Array | |
|
| 0492 | Construct the Rectangle | Math | |
|
| 0498 | Diagonal Traverse | Array, Matrix, Simulation | |
|
| 0502 | IPO | Array, Greedy, Sorting, Heap (Priority Queue) | |
|
| 0504 | Base 7 | Math | |
|
| 0506 | Relative Ranks | Array, Sorting, Heap | |
|
| 0507 | Perfect Number | Math | |
|
| 0509 | Fibonacci Number | Math, Recursion, DP, Memoization | |
|
| 0516 | Longest Palindromic Subsequence | String, DP | |
|
| 0518 | Coin Change 2 | Array, DP | |
|
| 0530 | Minimum Absolute Difference in BST | Tree, Depth-First Search, Breadth-First Search, BST, Binary Tree | |
|
| 0540 | Single Element in a Sorted Array | Array, BS | |
|
| 0541 | Reverse String II | Two Pointers, String | |
|
| 0543 | Diameter of Binary Tree | Tree, DFS, Binary Tree | |
|
| 0605 | Can Place Flowers | Array, Greedy | |
|
| 0652 | Find Duplicate Subtrees | Hash Table, Tree, Depth-First Search, Binary Tree | |
|
| 0653 | Two Sum IV - Input is a BST | Tree, DFS, BST, Binary Tree | |
|
| 0695 | Max Area of Island | Array, Depth-First Search, Breadth-First Search, Union Find, Matrix | |
|
| 0704 | Binary Search | Array, Binary Search | |
|
| 0739 | Daily Temperatures | Array, Stack, Monotonic Stack | |
|
| 0771 | Jewels and Stones | String, Hashtable | |
|
| 0799 | Minimum Distance Between BST Nodes | Tree, Depth-First Search, Breadth-First Search, BST, Binary Tree | |
|
| 0875 | Koko Eating Bananas | Array, BS | |
|
| 0876 | Middle of the Linked List | Linked List, Two Pointers | |
|
| 0888 | Fair Candy Swap | Array, Hash Table, Binary Search, Sorting | |
|
| 0912 | Sort an Array | Array, DNC, Sorting, Heap (Priority Queue), Merge Sort, Bucket Sort, Radix Sort, Counting Sort | |
|
| 0944 | Delete Columns to Make Sorted | Array, String | |
|
| 0958 | Check Completeness of a Binary Tree | Tree, Breadth-First Search, Binary Tree | |
|
| 0997 | Find the Town Judge | Array, Hash Table, Graph | |
|
| 1011 | Capacity To Ship Packages Within D Days | Array, BS | |
|
| 1029 | Two City Scheduling | Array, Greedy, Sorting | |
|
| 1047 | Remove All Adjacent Duplicates In String | String, Stack | |
|
| 1092 | Shortest Common Supersequence | String, DP | |
|
| 1108 | Defanging an IP Address | String | |
|
| 1143 | Longest Common Subsequence | String, DP | |
|
| 1232 | Check If It Is a Straight Line | Array, Math, Geometry | |
|
| 1345 | Jump Game IV | Array, Hash Table, Breadth-First Search | |
|
| 1431 | Kids With the Greatest Number of Candies | Array | |
|
| 1461 | Check If a String Contains All Binary Codes of Size K | String, Hash Table, Bit Manipulation | |
|
| 1472 | Design Browser History | Array, LL, ST, Design, Doubly-Linked List, Data Stream | |
|
| 1480 | Running Sum of 1d Array | Array, Prefix Sum | |
|
| 1491 | Average Salary Excluding the Minimum and Maximum | Array, Sorting | |
|
| 1498 | Number of Subsequences That Satisfy the Given Sum Condition | Array, Two Pointer, Binary Search, Sorting | |
|
| 1512 | Number of Good Pairs | Array, Hash Table, Math, Counting | |
|
| 1537 | Get the Maximum Score | Array, Two Pointer, DP, Greedy | |
|
| 1539 | Kth Missing Positive Number | Array, BS | |
|
| 1580 | Shuffle the Array | Array | |
|
| 1630 | Count Odd Numbers in an Interval Range | Math | |
|
| 1672 | Richest Customer Wealth | Array, Matrix | |
|
| 1689 | Partitioning Into Minimum Number Of Deci-Binary Numbers | String, Greedy | |
|
| 1920 | Build Array from Permutation | Array, Simulation | |
|
| 1929 | Concatenation of Array | Array | |
|
| 1957 | Delete Characters to Make Fancy String | String | |
|
| 2011 | Final Value of Variable After Performing Operations | Array, String, Simulation | |
|
| 2114 | Maximum Number of Words Found in Sentences | Array, String | |
|
| 2160 | Minimum Sum of Four Digit Number After Splitting Digits | Math, Greedy, Sorting | |
|
| 2176 | Count Equal and Divisible Pairs in an Array | Array | |
|
| 2187 | Minimum Time to Complete Trips | Array, BS | |
|
| 2235 | Add Two Integers | Math | |
|
| 2236 | Root Equal to Sum of Children | Tree, Binary Tree | |
|
| 2348 | Number of Zero-Filled Subarrays | Array, Math | |
|
| 2396 | Strictly Palindromic Number | Math, 2P, Brainteaser | |
|
| 2413 | Smallest Even Multiple | Math, Number Theory | |
|
| 2427 | Number of Common Factors | Math, Enumeration, Number Theory | |
|
| 2444 | Count Subarrays With Fixed Bounds | Array, Q, Sliding Window, Monotonic Queue | |
|
| 2469 | Convert the Temperature | Math | |
|
| 2551 | Put Marbles in Bags | Array, Greedy, Sorting, Heap (Priority Queue) | |
|
| 2574 | Left and Right Sum Differences | Array, Prefix Sum | |
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