| 2 | Add Two Numbers | Linked ListMathRecursion | Medium |
| 3 | Longest Substring Without Repeating Characters | Hash TableStringSliding Window | Medium |
| 5 | Longest Palindromic Substring | Two PointersStringDynamic Programming | Medium |
| 6 | Zigzag Conversion | String | Medium |
| 7 | Reverse Integer | Math | Medium |
| 8 | String to Integer (atoi) | String | Medium |
| 11 | Container With Most Water | ArrayTwo PointersGreedy | Medium |
| 12 | Integer to Roman | Hash TableMathString | Medium |
| 15 | 3Sum | ArrayTwo PointersSorting | Medium |
| 16 | 3Sum Closest | ArrayTwo PointersSorting | Medium |
| 17 | Letter Combinations of a Phone Number | Hash TableStringBacktracking | Medium |
| 18 | 4Sum | ArrayTwo PointersSorting | Medium |
| 19 | Remove Nth Node From End of List | Linked ListTwo Pointers | Medium |
| 22 | Generate Parentheses | StringDynamic ProgrammingBacktracking | Medium |
| 24 | Swap Nodes in Pairs | Linked ListRecursion | Medium |
| 29 | Divide Two Integers | MathBit Manipulation | Medium |
| 31 | Next Permutation | ArrayTwo Pointers | Medium |
| 33 | Search in Rotated Sorted Array | ArrayBinary Search | Medium |
| 34 | Find First and Last Position of Element in Sorted Array | ArrayBinary Search | Medium |
| 36 | Valid Sudoku | ArrayHash TableMatrix | Medium |
| 38 | Count and Say | String | Medium |
| 39 | Combination Sum | ArrayBacktracking | Medium |
| 40 | Combination Sum II | ArrayBacktracking | Medium |
| 43 | Multiply Strings | MathStringSimulation | Medium |
| 45 | Jump Game II | ArrayDynamic ProgrammingGreedy | Medium |
| 46 | Permutations | ArrayBacktracking | Medium |
| 47 | Permutations II | ArrayBacktrackingSorting | Medium |
| 48 | Rotate Image | ArrayMathMatrix | Medium |
| 49 | Group Anagrams | ArrayHash TableString+1 | Medium |
| 50 | Pow(x, n) | MathRecursion | Medium |
| 53 | Maximum Subarray | ArrayDivide and ConquerDynamic Programming | Medium |
| 54 | Spiral Matrix | ArrayMatrixSimulation | Medium |
| 55 | Jump Game | ArrayDynamic ProgrammingGreedy | Medium |
| 56 | Merge Intervals | ArraySorting | Medium |
| 57 | Insert Interval | Array | Medium |
| 59 | Spiral Matrix II | ArrayMatrixSimulation | Medium |
| 61 | Rotate List | Linked ListTwo Pointers | Medium |
| 62 | Unique Paths | MathDynamic ProgrammingCombinatorics | Medium |
| 63 | Unique Paths II | ArrayDynamic ProgrammingMatrix | Medium |
| 64 | Minimum Path Sum | ArrayDynamic ProgrammingMatrix | Medium |
| 71 | Simplify Path | StringStack | Medium |
| 72 | Edit Distance | StringDynamic Programming | Medium |
| 73 | Set Matrix Zeroes | ArrayHash TableMatrix | Medium |
| 74 | Search a 2D Matrix | ArrayBinary SearchMatrix | Medium |
| 75 | Sort Colors | ArrayTwo PointersSorting | Medium |
| 77 | Combinations | Backtracking | Medium |
| 78 | Subsets | ArrayBacktrackingBit Manipulation | Medium |
| 79 | Word Search | ArrayStringBacktracking+2 | Medium |
| 80 | Remove Duplicates from Sorted Array II | ArrayTwo Pointers | Medium |
| 81 | Search in Rotated Sorted Array II | ArrayBinary Search | Medium |