All companies
Apple
77 Easy180 Medium46 Hard303 total
| No. | Problem | Difficulty | Frequency |
|---|---|---|---|
| 146 | LRU Cache | Medium | |
| 1 | Two Sum | Easy | |
| 56 | Merge Intervals | Medium | |
| 200 | Number of Islands | Medium | |
| 3 | Longest Substring Without Repeating Characters | Medium | |
| 14 | Longest Common Prefix | Easy | |
| 20 | Valid Parentheses | Easy | |
| 36 | Valid Sudoku | Medium | |
| 48 | Rotate Image | Medium | |
| 49 | Group Anagrams | Medium | |
| 121 | Best Time to Buy and Sell Stock | Easy | |
| 125 | Valid Palindrome | Easy | |
| 151 | Reverse Words in a String | Medium | |
| 189 | Rotate Array | Medium | |
| 206 | Reverse Linked List | Easy | |
| 207 | Course Schedule | Medium | |
| 210 | Course Schedule II | Medium | |
| 215 | Kth Largest Element in an Array | Medium | |
| 238 | Product of Array Except Self | Medium | |
| 347 | Top K Frequent Elements | Medium | |
| 362 | Design Hit Counter | Medium | |
| 4 | Median of Two Sorted Arrays | Hard | |
| 7 | Reverse Integer | Medium | |
| 15 | 3Sum | Medium | |
| 21 | Merge Two Sorted Lists | Easy | |
| 23 | Merge k Sorted Lists | Hard | |
| 28 | Find the Index of the First Occurrence in a String | Easy | |
| 34 | Find First and Last Position of Element in Sorted Array | Medium | |
| 42 | Trapping Rain Water | Hard | |
| 53 | Maximum Subarray | Medium | |
| 54 | Spiral Matrix | Medium | |
| 70 | Climbing Stairs | Easy | |
| 88 | Merge Sorted Array | Easy | |
| 102 | Binary Tree Level Order Traversal | Medium | |
| 118 | Pascal's Triangle | Easy | |
| 122 | Best Time to Buy and Sell Stock II | Medium | |
| 127 | Word Ladder | Hard | |
| 139 | Word Break | Medium | |
| 155 | Min Stack | Medium | |
| 165 | Compare Version Numbers | Medium | |
| 190 | Reverse Bits | Easy | |
| 191 | Number of 1 Bits | Easy | |
| 208 | Implement Trie (Prefix Tree) | Medium | |
| 227 | Basic Calculator II | Medium | |
| 236 | Lowest Common Ancestor of a Binary Tree | Medium | |
| 240 | Search a 2D Matrix II | Medium | |
| 253 | Meeting Rooms II | Medium | |
| 283 | Move Zeroes | Easy | |
| 284 | Peeking Iterator | Medium | |
| 295 | Find Median from Data Stream | Hard | |
| 348 | Design Tic-Tac-Toe | Medium | |
| 380 | Insert Delete GetRandom O(1) | Medium | |
| 383 | Ransom Note | Easy | |
| 443 | String Compression | Medium | |
| 560 | Subarray Sum Equals K | Medium | |
| 713 | Subarray Product Less Than K | Medium | |
| 622 | Design Circular Queue | Medium | |
| 981 | Time Based Key-Value Store | Medium | |
| 1146 | Snapshot Array | Medium | |
| 5 | Longest Palindromic Substring | Medium | |
| 10 | Regular Expression Matching | Hard | |
| 11 | Container With Most Water | Medium | |
| 17 | Letter Combinations of a Phone Number | Medium | |
| 19 | Remove Nth Node From End of List | Medium | |
| 22 | Generate Parentheses | Medium | |
| 26 | Remove Duplicates from Sorted Array | Easy | |
| 33 | Search in Rotated Sorted Array | Medium | |
| 55 | Jump Game | Medium | |
| 68 | Text Justification | Hard | |
| 69 | Sqrt(x) | Easy | |
| 104 | Maximum Depth of Binary Tree | Easy | |
| 128 | Longest Consecutive Sequence | Medium | |
| 149 | Max Points on a Line | Hard | |
| 167 | Two Sum II - Input Array Is Sorted | Medium | |
| 221 | Maximal Square | Medium | |
| 232 | Implement Queue using Stacks | Easy | |
| 237 | Delete Node in a Linked List | Medium | |
| 252 | Meeting Rooms | Easy | |
| 257 | Binary Tree Paths | Easy | |
| 273 | Integer to English Words | Hard | |
| 297 | Serialize and Deserialize Binary Tree | Hard | |
| 341 | Flatten Nested List Iterator | Medium | |
| 344 | Reverse String | Easy | |
| 387 | First Unique Character in a String | Easy | |
| 394 | Decode String | Medium | |
| 565 | Array Nesting | Medium | |
| 621 | Task Scheduler | Medium | |
| 658 | Find K Closest Elements | Medium | |
| 714 | Best Time to Buy and Sell Stock with Transaction Fee | Medium | |
| 733 | Flood Fill | Easy | |
| 706 | Design HashMap | Easy | |
| 509 | Fibonacci Number | Easy | |
| 996 | Number of Squareful Arrays | Hard | |
| 1047 | Remove All Adjacent Duplicates In String | Easy | |
| 1275 | Find Winner on a Tic Tac Toe Game | Easy | |
| 2023 | Number of Pairs of Strings With Concatenation Equal to Target | Medium | |
| 2397 | Maximum Rows Covered by Columns | Medium | |
| 2972 | Count the Number of Incremovable Subarrays II | Hard | |
| 2970 | Count the Number of Incremovable Subarrays I | Easy | |
| 3030 | Find the Grid of Region Average | Medium | |
| 3522 | Calculate Score After Performing Instructions | Medium | |
| 1606 | Find Servers That Handled Most Number of Requests | Hard | |
| 2 | Add Two Numbers | Medium | |
| 8 | String to Integer (atoi) | Medium | |
| 13 | Roman to Integer | Easy | |
| 39 | Combination Sum | Medium | |
| 46 | Permutations | Medium | |
| 57 | Insert Interval | Medium | |
| 71 | Simplify Path | Medium | |
| 73 | Set Matrix Zeroes | Medium | |
| 75 | Sort Colors | Medium | |
| 79 | Word Search | Medium | |
| 92 | Reverse Linked List II | Medium | |
| 97 | Interleaving String | Medium | |
| 123 | Best Time to Buy and Sell Stock III | Hard | |
| 124 | Binary Tree Maximum Path Sum | Hard | |
| 134 | Gas Station | Medium | |
| 143 | Reorder List | Medium | |
| 162 | Find Peak Element | Medium | |
| 188 | Best Time to Buy and Sell Stock IV | Hard | |
| 198 | House Robber | Medium | |
| 202 | Happy Number | Easy | |
| 239 | Sliding Window Maximum | Hard | |
| 242 | Valid Anagram | Easy | |
| 268 | Missing Number | Easy | |
| 274 | H-Index | Medium | |
| 314 | Binary Tree Vertical Order Traversal | Medium | |
| 322 | Coin Change | Medium | |
| 328 | Odd Even Linked List | Medium | |
| 378 | Kth Smallest Element in a Sorted Matrix | Medium | |
| 412 | Fizz Buzz | Easy | |
| 460 | LFU Cache | Hard | |
| 468 | Validate IP Address | Medium | |
| 647 | Palindromic Substrings | Medium | |
| 787 | Cheapest Flights Within K Stops | Medium | |
| 876 | Middle of the Linked List | Easy | |
| 994 | Rotting Oranges | Medium | |
| 1011 | Capacity To Ship Packages Within D Days | Medium | |
| 3074 | Apple Redistribution into Boxes | Easy | |
| 688 | Knight Probability in Chessboard | Medium | |
| 1650 | Lowest Common Ancestor of a Binary Tree III | Medium | |
| 895 | Maximum Frequency Stack | Hard | |
| 855 | Exam Room | Medium | |
| 2591 | Distribute Money to Maximum Children | Easy | |
| 269 | Alien Dictionary | Hard | |
| 841 | Keys and Rooms | Medium | |
| 635 | Design Log Storage System | Medium | |
| 211 | Design Add and Search Words Data Structure | Medium | |
| 112 | Path Sum | Easy | |
| 2065 | Maximum Path Quality of a Graph | Hard | |
| 309 | Best Time to Buy and Sell Stock with Cooldown | Medium | |
| 108 | Convert Sorted Array to Binary Search Tree | Easy | |
| 2150 | Find All Lonely Numbers in the Array | Medium | |
| 2502 | Design Memory Allocator | Medium | |
| 477 | Total Hamming Distance | Medium | |
| 1087 | Brace Expansion | Medium | |
| 428 | Serialize and Deserialize N-ary Tree | Hard | |
| 72 | Edit Distance | Medium | |
| 6 | Zigzag Conversion | Medium | |
| 18 | 4Sum | Medium | |
| 25 | Reverse Nodes in k-Group | Hard | |
| 27 | Remove Element | Easy | |
| 41 | First Missing Positive | Hard | |
| 45 | Jump Game II | Medium | |
| 47 | Permutations II | Medium | |
| 67 | Add Binary | Easy | |
| 74 | Search a 2D Matrix | Medium | |
| 76 | Minimum Window Substring | Hard | |
| 84 | Largest Rectangle in Histogram | Hard | |
| 90 | Subsets II | Medium | |
| 91 | Decode Ways | Medium | |
| 98 | Validate Binary Search Tree | Medium | |
| 100 | Same Tree | Easy | |
| 101 | Symmetric Tree | Easy | |
| 138 | Copy List with Random Pointer | Medium | |
| 150 | Evaluate Reverse Polish Notation | Medium | |
| 153 | Find Minimum in Rotated Sorted Array | Medium | |
| 160 | Intersection of Two Linked Lists | Easy | |
| 176 | Second Highest Salary | Medium | |
| 203 | Remove Linked List Elements | Easy | |
| 204 | Count Primes | Medium | |
| 213 | House Robber II | Medium | |
| 217 | Contains Duplicate | Easy | |
| 218 | The Skyline Problem | Hard | |
| 219 | Contains Duplicate II | Easy | |
| 224 | Basic Calculator | Hard | |
| 225 | Implement Stack using Queues | Easy | |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Medium | |
| 278 | First Bad Version | Easy | |
| 332 | Reconstruct Itinerary | Hard | |
| 345 | Reverse Vowels of a String | Easy | |
| 349 | Intersection of Two Arrays | Easy | |
| 355 | Design Twitter | Medium | |
| 424 | Longest Repeating Character Replacement | Medium | |
| 438 | Find All Anagrams in a String | Medium | |
| 463 | Island Perimeter | Easy | |
| 485 | Max Consecutive Ones | Easy | |
| 493 | Reverse Pairs | Hard | |
| 503 | Next Greater Element II | Medium | |
| 515 | Find Largest Value in Each Tree Row | Medium | |
| 523 | Continuous Subarray Sum | Medium | |
| 542 | 01 Matrix | Medium | |
| 543 | Diameter of Binary Tree | Easy | |
| 605 | Can Place Flowers | Easy | |
| 628 | Maximum Product of Three Numbers | Easy | |
| 680 | Valid Palindrome II | Easy | |
| 692 | Top K Frequent Words | Medium | |
| 839 | Similar String Groups | Hard | |
| 849 | Maximize Distance to Closest Person | Medium | |
| 867 | Transpose Matrix | Easy | |
| 528 | Random Pick with Weight | Medium | |
| 885 | Spiral Matrix III | Medium | |
| 907 | Sum of Subarray Minimums | Medium | |
| 909 | Snakes and Ladders | Medium | |
| 953 | Verifying an Alien Dictionary | Easy | |
| 973 | K Closest Points to Origin | Medium | |
| 1249 | Minimum Remove to Make Valid Parentheses | Medium | |
| 1352 | Product of the Last K Numbers | Medium | |
| 1570 | Dot Product of Two Sparse Vectors | Medium | |
| 1657 | Determine if Two Strings Are Close | Medium | |
| 2104 | Sum of Subarray Ranges | Medium | |
| 2351 | First Letter to Appear Twice | Easy | |
| 317 | Shortest Distance from All Buildings | Hard | |
| 1242 | Web Crawler Multithreaded | Medium | |
| 291 | Word Pattern II | Medium | |
| 759 | Employee Free Time | Hard | |
| 769 | Max Chunks To Make Sorted | Medium | |
| 3163 | String Compression III | Medium | |
| 103 | Binary Tree Zigzag Level Order Traversal | Medium | |
| 1041 | Robot Bounded In Circle | Medium | |
| 2788 | Split Strings by Separator | Easy | |
| 824 | Goat Latin | Easy | |
| 2347 | Best Poker Hand | Easy | |
| 843 | Guess the Word | Hard | |
| 480 | Sliding Window Median | Hard | |
| 359 | Logger Rate Limiter | Easy | |
| 661 | Image Smoother | Easy | |
| 1197 | Minimum Knight Moves | Medium | |
| 133 | Clone Graph | Medium | |
| 126 | Word Ladder II | Hard | |
| 874 | Walking Robot Simulation | Medium | |
| 340 | Longest Substring with At Most K Distinct Characters | Medium | |
| 724 | Find Pivot Index | Easy | |
| 1213 | Intersection of Three Sorted Arrays | Easy | |
| 157 | Read N Characters Given Read4 | Easy | |
| 1472 | Design Browser History | Medium | |
| 1168 | Optimize Water Distribution in a Village | Hard | |
| 158 | Read N Characters Given read4 II - Call Multiple Times | Hard | |
| 1143 | Longest Common Subsequence | Medium | |
| 3613 | Minimize Maximum Component Cost | Medium | |
| 199 | Binary Tree Right Side View | Medium | |
| 820 | Short Encoding of Words | Medium | |
| 30 | Substring with Concatenation of All Words | Hard | |
| 173 | Binary Search Tree Iterator | Medium | |
| 243 | Shortest Word Distance | Easy | |
| 1870 | Minimum Speed to Arrive on Time | Medium | |
| 37 | Sudoku Solver | Hard | |
| 731 | My Calendar II | Medium | |
| 986 | Interval List Intersections | Medium | |
| 1091 | Shortest Path in Binary Matrix | Medium | |
| 109 | Convert Sorted List to Binary Search Tree | Medium | |
| 1854 | Maximum Population Year | Easy | |
| 338 | Counting Bits | Easy | |
| 737 | Sentence Similarity II | Medium | |
| 2435 | Paths in Matrix Whose Sum Is Divisible by K | Hard | |
| 329 | Longest Increasing Path in a Matrix | Hard | |
| 277 | Find the Celebrity | Medium | |
| 707 | Design Linked List | Medium | |
| 535 | Encode and Decode TinyURL | Medium | |
| 365 | Water and Jug Problem | Medium | |
| 209 | Minimum Size Subarray Sum | Medium | |
| 435 | Non-overlapping Intervals | Medium | |
| 490 | The Maze | Medium | |
| 933 | Number of Recent Calls | Easy | |
| 399 | Evaluate Division | Medium | |
| 912 | Sort an Array | Medium | |
| 455 | Assign Cookies | Easy | |
| 212 | Word Search II | Hard | |
| 1229 | Meeting Scheduler | Medium | |
| 695 | Max Area of Island | Medium | |
| 3019 | Number of Changing Keys | Easy | |
| 161 | One Edit Distance | Medium | |
| 636 | Exclusive Time of Functions | Medium | |
| 931 | Minimum Falling Path Sum | Medium | |
| 567 | Permutation in String | Medium | |
| 918 | Maximum Sum Circular Subarray | Medium | |
| 82 | Remove Duplicates from Sorted List II | Medium | |
| 889 | Construct Binary Tree from Preorder and Postorder Traversal | Medium | |
| 2633 | Convert Object to JSON String | Medium | |
| 346 | Moving Average from Data Stream | Easy | |
| 863 | All Nodes Distance K in Binary Tree | Medium | |
| 432 | All O`one Data Structure | Hard | |
| 1392 | Longest Happy Prefix | Hard | |
| 736 | Parse Lisp Expression | Hard | |
| 110 | Balanced Binary Tree | Easy | |
| 1740 | Find Distance in a Binary Tree | Medium | |
| 678 | Valid Parenthesis String | Medium | |
| 3408 | Design Task Manager | Medium | |
| 875 | Koko Eating Bananas | Medium | |
| 670 | Maximum Swap | Medium | |
| 496 | Next Greater Element I | Easy | |
| 729 | My Calendar I | Medium | |
| 785 | Is Graph Bipartite? | Medium |