| 539 | Minimum Time Difference | Medium |
| 541 | Reverse String II | Easy |
| 551 | Student Attendance Record I | Easy |
| 556 | Next Greater Element III | Medium |
| 557 | Reverse Words in a String III | Easy |
| 564 | Find the Closest Palindrome | Hard |
| 567 | Permutation in String | Medium |
| 583 | Delete Operation for Two Strings | Medium |
| 591 | Tag Validator | Hard |
| 592 | Fraction Addition and Subtraction | Medium |
| 599 | Minimum Index Sum of Two Lists | Easy |
| 606 | Construct String from Binary Tree | Easy |
| 609 | Find Duplicate File in System | Medium |
| 639 | Decode Ways II | Hard |
| 640 | Solve the Equation | Medium |
| 647 | Palindromic Substrings | Medium |
| 648 | Replace Words | Medium |
| 649 | Dota2 Senate | Medium |
| 657 | Robot Return to Origin | Easy |
| 664 | Strange Printer | Hard |
| 676 | Implement Magic Dictionary | Medium |
| 677 | Map Sum Pairs | Medium |
| 678 | Valid Parenthesis String | Medium |
| 680 | Valid Palindrome II | Easy |
| 686 | Repeated String Match | Medium |
| 691 | Stickers to Spell Word | Hard |
| 692 | Top K Frequent Words | Medium |
| 696 | Count Binary Substrings | Easy |
| 709 | To Lower Case | Easy |
| 712 | Minimum ASCII Delete Sum for Two Strings | Medium |