Problems
Browse 154 curated LeetCode problems with approach summaries and pattern hints.
154 / 154
| # ↑ | Title | Difficulty | Pattern | Actions |
|---|---|---|---|---|
| 1 | Two Sum | Easy | Arrays & Hashing | |
| 2 | Add Two Numbers | Medium | Linked Lists | |
| 3 | Longest Substring Without Repeating Characters | Medium | Sliding Window | |
| 4 | Median of Two Sorted Arrays | Hard | Binary Search | |
| 5 | Longest Palindromic Substring | Medium | Dynamic Programming (1D) | |
| 7 | Reverse Integer | Medium | Bit Manipulation | |
| 10 | Regular Expression Matching | Hard | Dynamic Programming (2D) | |
| 11 | Container With Most Water | Medium | Two Pointers | |
| 15 | 3Sum | Medium | Two Pointers | |
| 17 | Letter Combinations of a Phone Number | Medium | Backtracking | |
| 19 | Remove Nth Node From End of List | Medium | Linked Lists | |
| 20 | Valid Parentheses | Easy | Stack | |
| 21 | Merge Two Sorted Lists | Easy | Linked Lists | |
| 22 | Generate Parentheses | Medium | Stack | |
| 23 | Merge k Sorted Lists | Hard | Linked Lists | |
| 25 | Reverse Nodes in k-Group | Hard | Linked Lists | |
| 33 | Search in Rotated Sorted Array | Medium | Binary Search | |
| 35 | Search Insert Position | Easy | Binary Search | |
| 36 | Valid Sudoku | Medium | Arrays & Hashing | |
| 39 | Combination Sum | Medium | Backtracking | |
| 40 | Combination Sum II | Medium | Backtracking | |
| 42 | Trapping Rain Water | Hard | Two Pointers | |
| 43 | Multiply Strings | Medium | Bit Manipulation | |
| 45 | Jump Game II | Medium | Greedy | |
| 46 | Permutations | Medium | Backtracking | |
| 48 | Rotate Image | Medium | Math & Geometry | |
| 49 | Group Anagrams | Medium | Arrays & Hashing | |
| 50 | Pow(x, n) | Medium | Math & Geometry | |
| 51 | N-Queens | Hard | Backtracking | |
| 53 | Maximum Subarray | Medium | Greedy | |
| 54 | Spiral Matrix | Medium | Math & Geometry | |
| 55 | Jump Game | Medium | Greedy | |
| 56 | Merge Intervals | Medium | Intervals | |
| 57 | Insert Interval | Medium | Intervals | |
| 62 | Unique Paths | Medium | Dynamic Programming (2D) | |
| 66 | Plus One | Easy | Math & Geometry | |
| 70 | Climbing Stairs | Easy | Dynamic Programming (1D) | |
| 72 | Edit Distance | Medium | Dynamic Programming (2D) | |
| 73 | Set Matrix Zeroes | Medium | Math & Geometry | |
| 74 | Search a 2D Matrix | Medium | Binary Search | |
| 76 | Minimum Window Substring | Hard | Sliding Window | |
| 78 | Subsets | Medium | Backtracking | |
| 79 | Word Search | Medium | Backtracking | |
| 84 | Largest Rectangle in Histogram | Hard | Stack | |
| 90 | Subsets II | Medium | Backtracking | |
| 91 | Decode Ways | Medium | Dynamic Programming (1D) | |
| 92 | Reverse Linked List II | Medium | Linked Lists | |
| 94 | Binary Tree Inorder Traversal | Easy | Trees | |
| 97 | Interleaving String | Medium | Dynamic Programming (2D) | |
| 98 | Validate Binary Search Tree | Medium | Trees | |
| 100 | Same Tree | Easy | Trees | |
| 102 | Binary Tree Level Order Traversal | Medium | Trees | |
| 104 | Maximum Depth of Binary Tree | Easy | Trees | |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | Medium | Trees | |
| 110 | Balanced Binary Tree | Easy | Trees | |
| 115 | Distinct Subsequences | Hard | Dynamic Programming (2D) | |
| 121 | Best Time to Buy and Sell Stock | Easy | Sliding Window | |
| 124 | Binary Tree Maximum Path Sum | Hard | Trees | |
| 125 | Valid Palindrome | Easy | Two Pointers | |
| 127 | Word Ladder | Hard | Graphs | |
| 128 | Longest Consecutive Sequence | Medium | Arrays & Hashing | |
| 130 | Surrounded Regions | Medium | Graphs | |
| 131 | Palindrome Partitioning | Medium | Backtracking | |
| 133 | Clone Graph | Medium | Graphs | |
| 134 | Gas Station | Medium | Greedy | |
| 136 | Single Number | Easy | Bit Manipulation | |
| 138 | Copy List with Random Pointer | Medium | Linked Lists | |
| 139 | Word Break | Medium | Dynamic Programming (1D) | |
| 141 | Linked List Cycle | Easy | Linked Lists | |
| 143 | Reorder List | Medium | Linked Lists | |
| 144 | Binary Tree Preorder Traversal | Easy | Trees | |
| 150 | Evaluate Reverse Polish Notation | Medium | Stack | |
| 152 | Maximum Product Subarray | Medium | Dynamic Programming (1D) | |
| 153 | Find Minimum in Rotated Sorted Array | Medium | Binary Search | |
| 155 | Min Stack | Medium | Stack | |
| 167 | Two Sum II - Input Array Is Sorted | Medium | Two Pointers | |
| 190 | Reverse Bits | Easy | Bit Manipulation | |
| 191 | Number of 1 Bits | Easy | Bit Manipulation | |
| 198 | House Robber | Medium | Dynamic Programming (1D) | |
| 199 | Binary Tree Right Side View | Medium | Trees | |
| 200 | Number of Islands | Medium | Graphs | |
| 202 | Happy Number | Easy | Math & Geometry | |
| 206 | Reverse Linked List | Easy | Linked Lists | |
| 207 | Course Schedule | Medium | Graphs | |
| 208 | Implement Trie (Prefix Tree) | Medium | Tries | |
| 209 | Minimum Size Subarray Sum | Medium | Sliding Window | |
| 210 | Course Schedule II | Medium | Graphs | |
| 211 | Design Add and Search Words Data Structure | Medium | Tries | |
| 212 | Word Search II | Hard | Tries | |
| 213 | House Robber II | Medium | Dynamic Programming (1D) | |
| 215 | Kth Largest Element in an Array | Medium | Heap / Priority Queue | |
| 217 | Contains Duplicate | Easy | Arrays & Hashing | |
| 226 | Invert Binary Tree | Easy | Trees | |
| 230 | Kth Smallest Element in a BST | Medium | Trees | |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Medium | Trees | |
| 238 | Product of Array Except Self | Medium | Arrays & Hashing | |
| 239 | Sliding Window Maximum | Hard | Sliding Window | |
| 242 | Valid Anagram | Easy | Arrays & Hashing | |
| 252 | Meeting Rooms | Easy | Intervals | |
| 253 | Meeting Rooms II | Medium | Intervals | |
| 261 | Graph Valid Tree | Medium | Graphs | |
| 268 | Missing Number | Easy | Bit Manipulation | |
| 271 | Encode and Decode Strings | Medium | Arrays & Hashing | |
| 287 | Find the Duplicate Number | Medium | Linked Lists | |
| 295 | Find Median from Data Stream | Hard | Heap / Priority Queue | |
| 297 | Serialize and Deserialize Binary Tree | Hard | Trees | |
| 300 | Longest Increasing Subsequence | Medium | Dynamic Programming (1D) | |
| 309 | Best Time to Buy and Sell Stock with Cooldown | Medium | Dynamic Programming (2D) | |
| 312 | Burst Balloons | Hard | Dynamic Programming (2D) | |
| 322 | Coin Change | Medium | Dynamic Programming (1D) | |
| 323 | Number of Connected Components in an Undirected Graph | Medium | Graphs | |
| 329 | Longest Increasing Path in a Matrix | Hard | Dynamic Programming (2D) | |
| 332 | Reconstruct Itinerary | Hard | Graphs | |
| 338 | Counting Bits | Easy | Bit Manipulation | |
| 347 | Top K Frequent Elements | Medium | Arrays & Hashing | |
| 355 | Design Twitter | Medium | Heap / Priority Queue | |
| 371 | Sum of Two Integers | Medium | Bit Manipulation | |
| 416 | Partition Equal Subset Sum | Medium | Dynamic Programming (1D) | |
| 417 | Pacific Atlantic Water Flow | Medium | Graphs | |
| 424 | Longest Repeating Character Replacement | Medium | Sliding Window | |
| 435 | Non-overlapping Intervals | Medium | Intervals | |
| 494 | Target Sum | Medium | Dynamic Programming (2D) | |
| 518 | Coin Change II | Medium | Dynamic Programming (2D) | |
| 543 | Diameter of Binary Tree | Easy | Trees | |
| 567 | Permutation in String | Medium | Sliding Window | |
| 572 | Subtree of Another Tree | Easy | Trees | |
| 621 | Task Scheduler | Medium | Heap / Priority Queue | |
| 647 | Palindromic Substrings | Medium | Dynamic Programming (1D) | |
| 659 | Encode and Decode Strings | Medium | Arrays & Hashing | |
| 678 | Valid Parenthesis String | Medium | Greedy | |
| 684 | Redundant Connection | Medium | Graphs | |
| 695 | Max Area of Island | Medium | Graphs | |
| 698 | Partition to K Equal Sum Subsets | Medium | Backtracking | |
| 703 | Kth Largest Element in a Stream | Easy | Heap / Priority Queue | |
| 704 | Binary Search | Easy | Binary Search | |
| 739 | Daily Temperatures | Medium | Stack | |
| 743 | Network Delay Time | Medium | Graphs | |
| 746 | Min Cost Climbing Stairs | Easy | Dynamic Programming (1D) | |
| 763 | Partition Labels | Medium | Greedy | |
| 787 | Cheapest Flights Within K Stops | Medium | Graphs | |
| 846 | Hand of Straights | Medium | Greedy | |
| 853 | Car Fleet | Medium | Stack | |
| 875 | Koko Eating Bananas | Medium | Binary Search | |
| 912 | Sort an Array | Medium | Arrays & Hashing | |
| 973 | K Closest Points to Origin | Medium | Heap / Priority Queue | |
| 981 | Time Based Key-Value Store | Medium | Binary Search | |
| 994 | Rotting Oranges | Medium | Graphs | |
| 1046 | Last Stone Weight | Easy | Heap / Priority Queue | |
| 1143 | Longest Common Subsequence | Medium | Dynamic Programming (2D) | |
| 1192 | Critical Connections in a Network | Hard | Graphs | |
| 1448 | Count Good Nodes in Binary Tree | Medium | Trees | |
| 1584 | Min Cost to Connect All Points | Medium | Graphs | |
| 1851 | Minimum Interval to Include Each Query | Hard | Intervals | |
| 2013 | Detect Squares | Medium | Math & Geometry |