| 623 | Add One Row to Tree | TreeDepth-First SearchBreadth-First Search+1 | Medium |
| 624 | Maximum Distance in Arrays | ArrayGreedy | Medium |
| 626 | Exchange Seats | Database | Medium |
| 627 | Swap Salary | Database | Easy |
| 628 | Maximum Product of Three Numbers | ArrayMathSorting | Easy |
| 629 | K Inverse Pairs Array | Dynamic Programming | Hard |
| 630 | Course Schedule III | ArrayGreedySorting+1 | Hard |
| 632 | Smallest Range Covering Elements from K Lists | ArrayHash TableGreedy+3 | Hard |
| 633 | Sum of Square Numbers | MathTwo PointersBinary Search | Medium |
| 636 | Exclusive Time of Functions | ArrayStack | Medium |
| 637 | Average of Levels in Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Easy |
| 638 | Shopping Offers | ArrayDynamic ProgrammingBacktracking+3 | Medium |
| 639 | Decode Ways II | StringDynamic Programming | Hard |
| 640 | Solve the Equation | MathStringSimulation | Medium |
| 641 | Design Circular Deque | ArrayLinked ListDesign+1 | Medium |
| 643 | Maximum Average Subarray I | ArraySliding Window | Easy |
| 645 | Set Mismatch | ArrayHash TableBit Manipulation+1 | Easy |
| 646 | Maximum Length of Pair Chain | ArrayDynamic ProgrammingGreedy+1 | Medium |
| 647 | Palindromic Substrings | Two PointersStringDynamic Programming | Medium |
| 648 | Replace Words | ArrayHash TableString+1 | Medium |
| 649 | Dota2 Senate | StringGreedyQueue | Medium |
| 650 | 2 Keys Keyboard | MathDynamic Programming | Medium |
| 652 | Find Duplicate Subtrees | Hash TableTreeDepth-First Search+1 | Medium |
| 653 | Two Sum IV - Input is a BST | Hash TableTwo PointersTree+4 | Easy |
| 654 | Maximum Binary Tree | ArrayDivide and ConquerStack+3 | Medium |
| 655 | Print Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Medium |
| 657 | Robot Return to Origin | StringSimulation | Easy |
| 658 | Find K Closest Elements | ArrayTwo PointersBinary Search+3 | Medium |
| 659 | Split Array into Consecutive Subsequences | ArrayHash TableGreedy+1 | Medium |
| 661 | Image Smoother | ArrayMatrix | Easy |
| 662 | Maximum Width of Binary Tree | TreeDepth-First SearchBreadth-First Search+1 | Medium |
| 664 | Strange Printer | StringDynamic Programming | Hard |
| 665 | Non-decreasing Array | Array | Medium |
| 667 | Beautiful Arrangement II | ArrayMath | Medium |
| 668 | Kth Smallest Number in Multiplication Table | MathBinary Search | Hard |
| 669 | Trim a Binary Search Tree | TreeDepth-First SearchBinary Search Tree+1 | Medium |
| 670 | Maximum Swap | MathGreedy | Medium |
| 671 | Second Minimum Node In a Binary Tree | TreeDepth-First SearchBinary Tree | Easy |
| 672 | Bulb Switcher II | MathBit ManipulationDepth-First Search+1 | Medium |
| 673 | Number of Longest Increasing Subsequence | ArrayDynamic ProgrammingBinary Indexed Tree+1 | Medium |
| 674 | Longest Continuous Increasing Subsequence | Array | Easy |
| 675 | Cut Off Trees for Golf Event | ArrayBreadth-First SearchHeap (Priority Queue)+1 | Hard |
| 676 | Implement Magic Dictionary | Hash TableStringDepth-First Search+2 | Medium |
| 677 | Map Sum Pairs | Hash TableStringDesign+1 | Medium |
| 678 | Valid Parenthesis String | StringDynamic ProgrammingStack+1 | Medium |
| 679 | 24 Game | ArrayMathBacktracking | Hard |
| 680 | Valid Palindrome II | Two PointersStringGreedy | Easy |
| 682 | Baseball Game | ArrayStackSimulation | Easy |
| 684 | Redundant Connection | Depth-First SearchBreadth-First SearchUnion Find+1 | Medium |
| 685 | Redundant Connection II | Depth-First SearchBreadth-First SearchUnion Find+1 | Hard |