Preparing for FAANG (Facebook, Amazon, Apple, Netflix, Google) interviews requires mastering data structures, algorithms, and system design. LeetCode is one of the best platforms to sharpen problem-solving skills.
In this guide, we’ll cover 50 must-solve LeetCode problems, categorized by topic, with Difficulty.
| No. | Problem Title (Link to solution) | Leet Code# | Difficulty# | Topics |
|---|---|---|---|---|
| 1 | Two Sum | 1 | Easy | Array, Hash Table |
| 2 | Add Two Numbers | 2 | Medium | Linked List, Math |
| 3 | Longest Substring Without Repeating Characters | 3 | Medium | String, Sliding Window |
| 4 | Median of Two Sorted Arrays | 4 | Hard | Array, Binary Search, Divide & Conquer |
| 5 | Longest Palindromic Substring | 5 | Medium | String, Dynamic Programming |
| 6 | Container With Most Water | 11 | Medium | Array, Two Pointers |
| 7 | 3Sum | 15 | Medium | Array, Two Pointers |
| 8 | 4Sum | 18 | Medium | Array, Two Pointers |
| 9 | Letter Combinations of a Phone Number | 17 | Medium | String, Backtracking |
| 10 | Valid Parentheses | 20 | Easy | String, Stack |
| 11 | Merge Two Sorted Lists | 21 | Easy | Linked List |
| 12 | Remove Nth Node From End of List | 19 | Medium | Linked List, Two Pointers |
| 13 | Generate Parentheses | 22 | Medium | Backtracking, String |
| 14 | Merge k Sorted Lists | 23 | Hard | Linked List, Heap |
| 15 | Swap Nodes in Pairs | 24 | Medium | Linked List |
| 16 | Reverse Nodes in k-Group | 25 | Hard | Linked List |
| 17 | Valid Anagram | 242 | Easy | String, Hash Table |
| 18 | Group Anagrams | 49 | Medium | String, Hash Table, Sorting |
| 19 | Pow(x, n) | 50 | Medium | Math, Recursion |
| 20 | Combination Sum | 39 | Medium | Backtracking |
| 21 | Subsets | 78 | Medium | Backtracking, Bit Manipulation |
| 22 | Word Search | 79 | Medium | Backtracking, Matrix |
| 23 | Search in Rotated Sorted Array | 33 | Medium | Array, Binary Search |
| 24 | Find Minimum in Rotated Sorted Array | 153 | Medium | Array, Binary Search |
| 25 | Maximum Subarray | 53 | Easy | Array, Dynamic Programming |
| 26 | Spiral Matrix | 54 | Medium | Array, Matrix |
| 27 | Jump Game | 55 | Medium | Array, Greedy |
| 28 | Merge Intervals | 56 | Medium | Array, Sorting |
| 29 | Insert Interval | 57 | Medium | Array, Sorting |
| 30 | Unique Paths | 62 | Medium | Dynamic Programming, Combinatorics |
| 31 | Unique Paths II | 63 | Medium | Dynamic Programming |
| 32 | Minimum Path Sum | 64 | Medium | Dynamic Programming, Matrix |
| 33 | Valid Number | 65 | Hard | String, Parsing |
| 34 | Climbing Stairs | 70 | Easy | Dynamic Programming, Recursion |
| 35 | Simplify Path | 71 | Medium | Stack, String |
| 36 | Set Matrix Zeroes | 73 | Medium | Array, Matrix |
| 37 | Search a 2D Matrix | 74 | Medium | Array, Binary Search |
| 38 | Sort Colors | 75 | Medium | Array, Two Pointers |
| 39 | Minimum Window Substring | 76 | Hard | String, Sliding Window |
| 40 | Word Break | 139 | Medium | Dynamic Programming, String |
| 41 | Linked List Cycle | 141 | Easy | Linked List, Two Pointers |
| 42 | Reorder List | 143 | Medium | Linked List |
| 43 | Binary Tree Inorder Traversal | 94 | Medium | Tree, Stack, Recursion |
| 44 | Binary Tree Level Order Traversal | 102 | Medium | Tree, Breadth-First Search |
| 45 | Serialize and Deserialize Binary Tree | 297 | Hard | Tree, Design |
| 46 | Lowest Common Ancestor of a Binary Tree | 236 | Medium | Tree, Recursion |
| 47 | Number of Islands | 200 | Medium | Matrix, DFS/BFS |
| 48 | Course Schedule | 207 | Medium | Graph, Topological Sort |
| 49 | Word Ladder | 127 | Hard | Graph, Breadth-First Search |
| 50 | LRU Cache | 146 | Medium | Design, Hash Table, Linked List |
Feel free to explore each problem on LeetCode by searching for its title or number. Happy practicing!