| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | Hard |
| 387 | First Unique Character in a String | Easy |
| 389 | Find the Difference | Easy |
| 395 | Longest Substring with At Least K Repeating Characters | Medium |
| 398 | Random Pick Index | Medium |
| 409 | Longest Palindrome | Easy |
| 421 | Maximum XOR of Two Numbers in an Array | Medium |
| 423 | Reconstruct Original Digits from English | Medium |
| 424 | Longest Repeating Character Replacement | Medium |
| 432 | All O`one Data Structure | Hard |
| 433 | Minimum Genetic Mutation | Medium |
| 438 | Find All Anagrams in a String | Medium |
| 442 | Find All Duplicates in an Array | Medium |
| 447 | Number of Boomerangs | Medium |
| 448 | Find All Numbers Disappeared in an Array | Easy |
| 451 | Sort Characters By Frequency | Medium |
| 454 | 4Sum II | Medium |
| 457 | Circular Array Loop | Medium |
| 460 | LFU Cache | Hard |
| 480 | Sliding Window Median | Hard |
| 491 | Increasing Subsequences | Medium |
| 496 | Next Greater Element I | Easy |
| 500 | Keyboard Row | Easy |
| 508 | Most Frequent Subtree Sum | Medium |
| 519 | Random Flip Matrix | Medium |
| 522 | Longest Uncommon Subsequence II | Medium |
| 523 | Continuous Subarray Sum | Medium |
| 525 | Contiguous Array | Medium |
| 532 | K-diff Pairs in an Array | Medium |
| 535 | Encode and Decode TinyURL | Medium |