| 726 | Number of Atoms | Hash TableStringStack+1 | Hard |
| 730 | Count Different Palindromic Subsequences | StringDynamic Programming | Hard |
| 732 | My Calendar III | Binary SearchDesignSegment Tree+2 | Hard |
| 736 | Parse Lisp Expression | Hash TableStringStack+1 | Hard |
| 741 | Cherry Pickup | ArrayDynamic ProgrammingMatrix | Hard |
| 745 | Prefix and Suffix Search | ArrayHash TableString+2 | Hard |
| 749 | Contain Virus | ArrayDepth-First SearchBreadth-First Search+2 | Hard |
| 753 | Cracking the Safe | Depth-First SearchGraphEulerian Circuit | Hard |
| 757 | Set Intersection Size At Least Two | ArrayGreedySorting | Hard |
| 761 | Special Binary String | StringRecursion | Hard |
| 765 | Couples Holding Hands | GreedyDepth-First SearchBreadth-First Search+2 | Hard |
| 768 | Max Chunks To Make Sorted II | ArrayStackGreedy+2 | Hard |
| 770 | Basic Calculator IV | Hash TableMathString+2 | Hard |
| 773 | Sliding Puzzle | ArrayDynamic ProgrammingBacktracking+3 | Hard |
| 778 | Swim in Rising Water | ArrayBinary SearchDepth-First Search+4 | Hard |
| 780 | Reaching Points | Math | Hard |
| 782 | Transform to Chessboard | ArrayMathBit Manipulation+1 | Hard |
| 793 | Preimage Size of Factorial Zeroes Function | MathBinary Search | Hard |
| 798 | Smallest Rotation with Highest Score | ArrayPrefix Sum | Hard |
| 801 | Minimum Swaps To Make Sequences Increasing | ArrayDynamic Programming | Hard |
| 803 | Bricks Falling When Hit | ArrayUnion FindMatrix | Hard |
| 805 | Split Array With Same Average | ArrayMathDynamic Programming+2 | Hard |
| 810 | Chalkboard XOR Game | ArrayMathBit Manipulation+2 | Hard |
| 815 | Bus Routes | ArrayHash TableBreadth-First Search | Hard |
| 818 | Race Car | Dynamic Programming | Hard |
| 827 | Making A Large Island | ArrayDepth-First SearchBreadth-First Search+2 | Hard |
| 828 | Count Unique Characters of All Substrings of a Given String | Hash TableStringDynamic Programming | Hard |
| 829 | Consecutive Numbers Sum | MathEnumeration | Hard |
| 834 | Sum of Distances in Tree | Dynamic ProgrammingTreeDepth-First Search+1 | Hard |
| 839 | Similar String Groups | ArrayHash TableString+3 | Hard |
| 843 | Guess the Word | ArrayMathString+2 | Hard |
| 847 | Shortest Path Visiting All Nodes | Dynamic ProgrammingBit ManipulationBreadth-First Search+2 | Hard |
| 850 | Rectangle Area II | ArraySegment TreeLine Sweep+1 | Hard |
| 854 | K-Similar Strings | Hash TableStringBreadth-First Search | Hard |
| 857 | Minimum Cost to Hire K Workers | ArrayGreedySorting+1 | Hard |
| 862 | Shortest Subarray with Sum at Least K | ArrayBinary SearchQueue+4 | Hard |
| 864 | Shortest Path to Get All Keys | ArrayBit ManipulationBreadth-First Search+1 | Hard |
| 871 | Minimum Number of Refueling Stops | ArrayDynamic ProgrammingGreedy+1 | Hard |
| 878 | Nth Magical Number | MathBinary Search | Hard |
| 879 | Profitable Schemes | ArrayDynamic Programming | Hard |
| 882 | Reachable Nodes In Subdivided Graph | GraphHeap (Priority Queue)Shortest Path | Hard |
| 887 | Super Egg Drop | MathBinary SearchDynamic Programming | Hard |
| 891 | Sum of Subsequence Widths | ArrayMathSorting | Hard |
| 895 | Maximum Frequency Stack | Hash TableStackDesign+1 | Hard |
| 899 | Orderly Queue | MathStringSorting | Hard |
| 902 | Numbers At Most N Given Digit Set | ArrayMathString+2 | Hard |
| 903 | Valid Permutations for DI Sequence | StringDynamic ProgrammingPrefix Sum | Hard |
| 906 | Super Palindromes | MathStringEnumeration | Hard |
| 913 | Cat and Mouse | MathDynamic ProgrammingGraph+3 | Hard |
| 920 | Number of Music Playlists | MathDynamic ProgrammingCombinatorics | Hard |