| 1 | Two Sum | — | Easy | ArrayHash Table | 56% | |
| 3 | Longest Substring Without Repeating Characters | — | Medium | Hash TableStringSliding Window | 37% | |
| 12 | Integer to Roman | — | Medium | Hash TableMathString | 68% | |
| 13 | Roman to Integer | — | Easy | Hash TableMathString | 65% | |
| 17 | Letter Combinations of a Phone Number | — | Medium | Hash TableStringBacktracking | 64% | |
| 30 | Substring with Concatenation of All Words | — | Hard | Hash TableStringSliding Window | 33% | |
| 36 | Valid Sudoku | — | Medium | ArrayHash TableMatrix | 62% | |
| 37 | Sudoku Solver | — | Hard | ArrayHash TableBacktracking | 64% | |
| 41 | First Missing Positive | — | Hard | ArrayHash Table | 41% | |
| 49 | Group Anagrams | — | Medium | ArrayHash TableString | 71% | |
| 73 | Set Matrix Zeroes | — | Medium | ArrayHash TableMatrix | 60% | |
| 76 | Minimum Window Substring | — | Hard | Hash TableStringSliding Window | 45% | |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | — | Medium | ArrayHash TableDivide and Conquer | 67% | |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | — | Medium | ArrayHash TableDivide and Conquer | 66% | |
| 126 | Word Ladder II | — | Hard | Hash TableStringBacktracking | 27% | |
| 127 | Word Ladder | — | Hard | Hash TableStringBreadth-First Search | 42% | |
| 128 | Longest Consecutive Sequence | — | Medium | ArrayHash TableUnion Find | 47% | |
| 133 | Clone Graph | — | Medium | Hash TableDepth-First SearchBreadth-First Search | 62% | |
| 138 | Copy List with Random Pointer | — | Medium | Hash TableLinked List | 60% | |
| 139 | Word Break | — | Medium | ArrayHash TableString | 48% | |
| 140 | Word Break II | — | Hard | ArrayHash TableString | 53% | |
| 141 | Linked List Cycle | — | Easy | Hash TableLinked ListTwo Pointers | 52% | |
| 142 | Linked List Cycle II | — | Medium | Hash TableLinked ListTwo Pointers | 55% | |
| 146 | LRU Cache | — | Medium | Hash TableLinked ListDesign | 45% | |
| 149 | Max Points on a Line | — | Hard | ArrayHash TableMath | 29% | |
| 160 | Intersection of Two Linked Lists | — | Easy | Hash TableLinked ListTwo Pointers | 61% | |
| 166 | Fraction to Recurring Decimal | — | Medium | Hash TableMathString | 26% | |
| 169 | Majority Element | — | Easy | ArrayHash TableDivide and Conquer | 66% | |
| 187 | Repeated DNA Sequences | — | Medium | Hash TableStringBit Manipulation | 51% | |
| 202 | Happy Number | — | Easy | Hash TableMathTwo Pointers | 58% | |
| 205 | Isomorphic Strings | — | Easy | Hash TableString | 47% | |
| 208 | Implement Trie (Prefix Tree) | — | Medium | Hash TableStringDesign | 68% | |
| 217 | Contains Duplicate | — | Easy | ArrayHash TableSorting | 63% | |
| 219 | Contains Duplicate II | — | Easy | ArrayHash TableSliding Window | 49% | |
| 229 | Majority Element II | — | Medium | ArrayHash TableSorting | 54% | |
| 242 | Valid Anagram | — | Easy | Hash TableStringSorting | 66% | |
| 264 | Ugly Number II | — | Medium | Hash TableMathDynamic Programming | 49% | |
| 268 | Missing Number | — | Easy | ArrayHash TableMath | 70% | |
| 290 | Word Pattern | — | Easy | Hash TableString | 43% | |
| 299 | Bulls and Cows | — | Medium | Hash TableStringCounting | 51% | |
| 336 | Palindrome Pairs | — | Hard | ArrayHash TableString | 36% | |
| 347 | Top K Frequent Elements | — | Medium | ArrayHash TableDivide and Conquer | 64% | |
| 349 | Intersection of Two Arrays | — | Easy | ArrayHash TableTwo Pointers | 76% | |
| 350 | Intersection of Two Arrays II | — | Easy | ArrayHash TableTwo Pointers | 59% | |
| 355 | Design Twitter | — | Medium | Hash TableLinked ListDesign | 42% | |
| 380 | Insert Delete GetRandom O(1)read | — | Medium | ArrayHash TableMath | 55% | |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowedread | — | Hard | ArrayHash TableMath | 36% | |
| 383 | Ransom Note | — | Easy | Hash TableStringCounting | 64% | |
| 387 | First Unique Character in a String | — | Easy | Hash TableStringQueue | 64% | |
| 389 | Find the Difference | — | Easy | Hash TableStringBit Manipulation | 60% | |