FAANG Coding Interview Questions - 2025 Edition

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Two Sum | Easy | O(n) | O(n) | | 2 | Longest Substring Without Repeating Characters | Medium | O(n) | O(min(m,n)) | | 3 | Longest Palindromic Substring | Medium | O(n²) | O(1) | | 4 | Container With Most Water | Medium | O(n) | O(1) | | 5 | 3Sum | Medium | O(n²) | O(1) | | 6 | Remove Nth Node From End of List | Medium | O(n) | O(1) | | 7 | Valid Parentheses | Easy | O(n) | O(n) | | 8 | Merge Two Sorted Lists | Easy | O(n+m) | O(1) | | 9 | Merge k Sorted Lists | Hard | O(n log k) | O(1) | | 10 | Search in Rotated Sorted Array | Medium | O(log n) | O(1) | | 11 | Combination Sum | Medium | O(2ⁿ) | O(n) | | 12 | Rotate Image | Medium | O(n²) | O(1) | | 13 | Group Anagrams | Medium | O(n k log k) | O(n k) | | 14 | Maximum Subarray | Easy | O(n) | O(1) | | 15 | Spiral Matrix | Medium | O(m×n) | O(1) | | 16 | Jump Game | Medium | O(n) | O(1) | | 17 | Merge Intervals | Medium | O(n log n) | O(n) | | 18 | Insert Interval | Medium | O(n) | O(n) | | 19 | Unique Paths | Medium | O(m×n) | O(m×n) | | 20 | Climbing Stairs | Easy | O(n) | O(1) | | 21 | Set Matrix Zeroes | Medium | O(m×n) | O(1) | | 22 | Minimum Window Substring | Hard | O(n) | O(k) | | 23 | Word Search | Medium | O(m×n×4ᵏ) | O(k) | | 24 | Decode Ways | Medium | O(n) | O(n) | | 25 | Validate Binary Search Tree | Medium | O(n) | O(h) | | 26 | Same Tree | Easy | O(n) | O(h) | | 27 | Binary Tree Level Order Traversal | Medium | O(n) | O(n) | | 28 | Maximum Depth of Binary Tree | Easy | O(n) | O(h) | | 29 | Construct Binary Tree from Preorder and Inorder Traversal | Medium | O(n) | O(n) | | 30 | Best Time to Buy and Sell Stock | Easy | O(n) | O(1) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Two Sum | Easy | O(n) | O(n) | | 2 | Add Two Numbers | Medium | O(max(m,n)) | O(max(m,n)) | | 3 | Longest Substring Without Repeating Characters | Medium | O(n) | O(min(m,n)) | | 4 | Median of Two Sorted Arrays | Hard | O(log(min(m,n))) | O(1) | | 5 | Longest Palindromic Substring | Medium | O(n²) | O(1) | | 6 | ZigZag Conversion | Medium | O(n) | O(n) | | 7 | String to Integer (atoi) | Medium | O(n) | O(1) | | 8 | 3Sum | Medium | O(n²) | O(1) or O(n) | | 9 | Letter Combinations of a Phone Number | Medium | O(4ⁿ) | O(n) | | 10 | Valid Parentheses | Easy | O(n) | O(n) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Two Sum | Easy | O(n) | O(n) | | 2 | Add Two Numbers | Medium | O(max(m,n)) | O(max(m,n)) | | 3 | Median of Two Sorted Arrays | Hard | O(log(min(m,n))) | O(1) | | 4 | Longest Palindromic Substring | Medium | O(n²) | O(1) | | 5 | String to Integer (atoi) | Medium | O(n) | O(1) | | 6 | Roman to Integer | Easy | O(n) | O(1) | | 7 | 3Sum | Medium | O(n²) | O(1) or O(n) | | 8 | Valid Parentheses | Easy | O(n) | O(n) | | 9 | Merge Two Sorted Lists | Easy | O(n+m) | O(1) | | 10 | Merge k Sorted Lists | Hard | O(n log k) | O(1) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Regular Expression Matching | Hard | O(m×n) | O(m×n) | | 2 | Roman to Integer | Easy | O(n) | O(1) | | 3 | 3Sum | Medium | O(n²) | O(1) or O(n) | | 4 | Letter Combinations of a Phone Number | Medium | O(4ⁿ) | O(n) | | 5 | Valid Parentheses | Easy | O(n) | O(n) | | 6 | Merge k Sorted Lists | Hard | O(n log k) | O(1) | | 7 | Reverse Nodes in k-Group | Hard | O(n) | O(1) | | 8 | Remove Duplicates from Sorted Array | Easy | O(n) | O(1) | | 9 | Implement strStr() | Easy | O(n×m) | O(1) | | 10 | Search in Rotated Sorted Array | Medium | O(log n) | O(1) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Two Sum | Easy | O(n) | O(n) | | 2 | Insert Interval | Medium | O(n) | O(n) | | 3 | Text Justification | Hard | O(n) | O(n) | | 4 | Minimum Window Substring | Hard | O(n) | O(k) | | 5 | Maximal Rectangle | Hard | O(m×n) | O(n) | | 6 | The Skyline Problem | Hard | O(n log n) | O(n) | | 7 | Maximal Square | Medium | O(m×n) | O(m×n) | | 8 | Find Median from Data Stream | Hard | O(log n) insert, O(1) find | O(n) | | 9 | Bulls and Cows | Medium | O(n) | O(1) | | 10 | Count of Smaller Numbers After Self | Hard | O(n log n) | O(n) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Two Sum | Easy | O(n) | O(n) | | 2 | Insert Interval | Medium | O(n) | O(n) | | 3 | Text Justification | Hard | O(n) | O(n) | | 4 | Minimum Window Substring | Hard | O(n) | O(k) | | 5 | Maximal Rectangle | Hard | O(m×n) | O(n) | | 6 | The Skyline Problem | Hard | O(n log n) | O(n) | | 7 | Maximal Square | Medium | O(m×n) | O(m×n) | | 8 | Find Median from Data Stream | Hard | O(log n) insert, O(1) find | O(n) | | 9 | Bulls and Cows | Medium | O(n) | O(1) | | 10 | Count of Smaller Numbers After Self | Hard | O(n log n) | O(n) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Nested List Weight Sum II | Medium | O(n) | O(n) | | 2 | Shortest Word Distance II | Medium | O(n) | O(n) | | 3 | Closest Binary Search Tree Value II | Medium | O(n) | O(n) | | 4 | Two Sum III - Data structure design | Easy | O(n) | O(n) | | 5 | Nested List Weight Sum | Medium | O(n) | O(n) | | 6 | Max Stack | Medium | O(n) | O(n) | | 7 | Find Leaves of Binary Tree | Medium | O(n) | O(n) | | 8 | All O'one Data Structure | Hard | O(1) for each operation | O(n) | | 9 | Can Place Flowers | Easy | O(n) | O(1) | | 10 | Factor Combinations | Medium | O(2ⁿ) | O(n) | | 11 | Paint House | Medium | O(n) | O(1) | | 12 | Paint House II | Hard | O(n×k) | O(n) | | 13 | Evaluate Reverse Polish Notation | Medium | O(n) | O(n) | | 14 | Shortest Word Distance | Easy | O(n) | O(1) | | 15 | Text Justification | Hard | O(n) | O(n) | | 16 | Count Different Palindromic Subsequences | Hard | O(n²) | O(n²) | | 17 | Binary Tree Upside Down | Medium | O(n) | O(n) | | 18 | Max Points on a Line | Hard | O(n²) | O(n) | | 19 | Partition to K Equal Sum Subsets | Hard | O(n×2^n) | O(n) | | 20 | Insert Delete GetRandom O(1) | Medium | O(1) for each operation | O(n) | | 21 | Number of Islands | Medium | O(m×n) | O(m×n) | | 22 | Exclusive Time of Functions | Medium | O(n) | O(n) | | 23 | Valid Triangle Number | Medium | O(n²) | O(1) | | 24 | Valid Number | Medium | O(n) | O(1) | | 25 | Repeated DNA Sequences | Medium | O(n) | O(n) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | Add Two Numbers | Medium | O(max(m,n)) | O(max(m,n)) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | | --- | ------- | ---------- | --------------- | ---------------- | | 1 | LRU Cache | Medium | O(1) for each operation | O(n) | | 2 | Department Top Three Salaries | Hard | O(n log k) | O(n) |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | Notes | | --- | ------- | ---------- | --------------- | ---------------- | ----- | | 1 | LRU Cache | Medium | O(1) | O(capacity) | System design classic | | 2 | Time Based Key-Value Store | Medium | O(log n) | O(n) | Practical data structure | | 3 | Design Search Autocomplete System | Hard | O(p + q log q) | O(n) | Real-world system | | 4 | Implement Trie (Prefix Tree) | Medium | O(m) | O(ALPHABET_SIZE×N×M) | NLP applications | | 5 | Word Search II | Hard | O(m×n×4^s) | O(n) | Advanced trie usage | | 6 | Serialize and Deserialize Binary Tree | Hard | O(n) | O(n) | Data persistence | | 7 | Design In-Memory File System | Hard | O(m + k log k) | O(n) | Unix cd simulation | | 8 | LFU Cache | Hard | O(1) | O(capacity) | Advanced caching | | 9 | Design Twitter | Medium | O(n log n) | O(n) | Social media system | | 10 | Top K Frequent Elements | Medium | O(n log k) | O(n + k) | ML preprocessing | | 11 | K Closest Points to Origin | Medium | O(n log k) | O(k) | ML algorithms | | 12 | Merge k Sorted Lists | Hard | O(n log k) | O(1) | Distributed systems | | 13 | Course Schedule II | Medium | O(V + E) | O(V + E) | Dependency resolution | | 14 | Word Ladder | Hard | O(M²×N) | O(M²×N) | NLP transformations | | 15 | Minimum Window Substring | Hard | O(|s| + |t|) | O(|s| + |t|) | String processing | | 16 | Design Hit Counter | Medium | O(1) amortized | O(1) | Rate limiting | | 17 | Design Log Storage System | Medium | O(n) | O(n) | System monitoring | | 18 | Valid Parentheses | Easy | O(n) | O(n) | Code parsing | | 19 | Longest Increasing Path in a Matrix | Hard | O(m×n) | O(m×n) | DP optimization | | 20 | Maximum Subarray | Medium | O(n) | O(1) | ML loss functions |

| No. | Problem | Difficulty | Time Complexity | Space Complexity | Notes | | --- | ------- | ---------- | --------------- | ---------------- | ----- | | 1 | Binary Search | Easy | O(log n) | O(1) | Core algorithm | | 2 | Search Insert Position | Easy | O(log n) | O(1) | Binary search variant | | 3 | Find Peak Element | Medium | O(log n) | O(1) | Binary search on unsorted | | 4 | Search in Rotated Sorted Array | Medium | O(log n) | O(1) | Modified binary search | | 5 | Find Minimum in Rotated Sorted Array | Medium | O(log n) | O(1) | Rotation point | | 6 | Search a 2D Matrix | Medium | O(log(m*n)) | O(1) | 2D binary search | | 7 | Median of Two Sorted Arrays | Hard | O(log(min(m,n))) | O(1) | Advanced binary search | | 8 | Shortest Path in Binary Matrix | Medium | O(n²) | O(n²) | BFS shortest path | | 9 | Number of Islands | Medium | O(m×n) | O(m×n) | DFS/BFS | | 10 | Word Ladder | Hard | O(M²×N) | O(M²×N) | BFS word transformation | | 11 | Course Schedule | Medium | O(V+E) | O(V+E) | Topological sort | | 12 | Course Schedule II | Medium | O(V+E) | O(V+E) | Topological ordering | | 13 | Alien Dictionary | Hard | O(C) | O(1) | Topological sort | | 14 | Valid IP Addresses | Medium | O(3^4) | O(1) | IP validation | | 15 | LRU Cache | Medium | O(1) | O(capacity) | Data structure design | | 16 | Implement Trie (Prefix Tree) | Medium | O(m) | O(26×N×M) | Trie data structure | | 17 | Design Hit Counter | Medium | O(1) amortized | O(1) | Time series design | | 18 | Logger Rate Limiter | Easy | O(1) | O(M) | Rate limiting | | 19 | Print in Order | Easy | O(1) | O(1) | Concurrency | | 20 | Print FooBar Alternately | Medium | O(n) | O(1) | Concurrency/Threading |