| 1 | To lower case |  Easy |
| 2 | Anagrams | Easy |
| 3 | Compare strings | Easy |
| 4 | Reverse string | Easy |
| 5 | Reverse words | Easy |
| 6 | Kth smallest node in a binary search tree |  Medium |
| 7 | Reverse words 2 | Easy |
| 8 | Contains duplicate | Easy |
| 9 | Same tree | Easy |
| 10 | Reverse integer | Easy |
| 11 | Hamming weight | Easy |
| 12 | Missing number | Easy |
| 13 | Maximum subarray | Easy |
| 14 | Merge sorted lists |  Hard |
| 15 | Unique number | Easy |
| 16 | First unique character | Easy |
| 17 | Longest common prefix | Easy |
| 18 | Valid palindrome | Easy |
| 19 | Valid parentheses | Easy |
| 20 | Majority item | Easy |
| 21 | Find difference | Easy |
| 22 | Detect capital | Easy |
| 23 | Excel sheet column number | Easy |
| 24 | Count bits | Medium |
| 25 | Reverse bits | Easy |
| 26 | Linked list cycle | Easy |
| 27 | Climb stairs | Easy |
| 28 | Arrays intersection | Easy |
| 29 | Largest Number | Medium |
| 30 | Subarrays of sum K | Medium |
| 31 | Find array duplicates | Medium |
| 32 | Arrays intersection 2 | Easy |
| 33 | Longest continuous increasing subsequence | Easy |
| 34 | Longest increasing subsequence | Medium |
| 35 | Maximum average subarray | Easy |
| 36 | Add one | Easy |
| 37 | Smallest subarray | Medium |
| 38 | Hamming distance | Easy |
| 39 | Jewels and stones | Easy |
| 40 | Longest substring without repeating | Medium |
| 41 | Sum of the left leaves | Easy |
| 42 | Symmetric tree | Easy |
| 43 | Invert binary tree | Easy |
| 44 | Maximum depth of a binary tree | Easy |
| 45 | Minimum depth of a binary tree | Easy |
| 46 | Averages of levels in a binary tree | Easy |
| 47 | Level order traversal of a binary tree | Easy |
| 48 | Balanced binary tree | Easy |
| 49 | Binary tree path sum | Easy |
| 50 | Binary tree sum numbers | Medium |