| 330 | Patching Array | ArrayGreedy | Hard |
| 332 | Reconstruct Itinerary | Depth-First SearchGraphEulerian Circuit | Hard |
| 335 | Self Crossing | ArrayMathGeometry | Hard |
| 336 | Palindrome Pairs | ArrayHash TableString+1 | Hard |
| 352 | Data Stream as Disjoint Intervals | Binary SearchDesignOrdered Set | Hard |
| 354 | Russian Doll Envelopes | ArrayBinary SearchDynamic Programming+1 | Hard |
| 363 | Max Sum of Rectangle No Larger Than K | ArrayBinary SearchMatrix+2 | Hard |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | ArrayHash TableMath+2 | Hard |
| 391 | Perfect Rectangle | ArrayHash TableMath+2 | Hard |
| 403 | Frog Jump | ArrayDynamic Programming | Hard |
| 407 | Trapping Rain Water II | ArrayBreadth-First SearchHeap (Priority Queue)+1 | Hard |
| 410 | Split Array Largest Sum | ArrayBinary SearchDynamic Programming+2 | Hard |
| 420 | Strong Password Checker | StringGreedyHeap (Priority Queue) | Hard |
| 432 | All O`one Data Structure | Hash TableLinked ListDesign+1 | Hard |
| 440 | K-th Smallest in Lexicographical Order | Trie | Hard |
| 446 | Arithmetic Slices II - Subsequence | ArrayDynamic Programming | Hard |
| 458 | Poor Pigs | MathDynamic ProgrammingCombinatorics | Hard |
| 460 | LFU Cache | Hash TableLinked ListDesign+1 | Hard |
| 466 | Count The Repetitions | StringDynamic Programming | Hard |
| 472 | Concatenated Words | ArrayStringDynamic Programming+3 | Hard |
| 479 | Largest Palindrome Product | MathEnumeration | Hard |
| 480 | Sliding Window Median | ArrayHash TableSliding Window+1 | Hard |
| 483 | Smallest Good Base | MathBinary Search | Hard |
| 488 | Zuma Game | StringDynamic ProgrammingStack+2 | Hard |
| 493 | Reverse Pairs | ArrayBinary SearchDivide and Conquer+4 | Hard |
| 502 | IPO | ArrayGreedySorting+1 | Hard |
| 514 | Freedom Trail | StringDynamic ProgrammingDepth-First Search+1 | Hard |
| 517 | Super Washing Machines | ArrayGreedy | Hard |
| 546 | Remove Boxes | ArrayDynamic ProgrammingMemoization | Hard |
| 552 | Student Attendance Record II | Dynamic Programming | Hard |
| 564 | Find the Closest Palindrome | MathString | Hard |
| 587 | Erect the Fence | ArrayMathGeometry | Hard |
| 591 | Tag Validator | StringStack | Hard |
| 600 | Non-negative Integers without Consecutive Ones | Dynamic Programming | Hard |
| 601 | Human Traffic of Stadium | Database | Hard |
| 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 |
| 639 | Decode Ways II | StringDynamic Programming | Hard |
| 664 | Strange Printer | StringDynamic Programming | Hard |
| 668 | Kth Smallest Number in Multiplication Table | MathBinary Search | Hard |
| 675 | Cut Off Trees for Golf Event | ArrayBreadth-First SearchHeap (Priority Queue)+1 | Hard |
| 679 | 24 Game | ArrayMathBacktracking | Hard |
| 685 | Redundant Connection II | Depth-First SearchBreadth-First SearchUnion Find+1 | Hard |
| 689 | Maximum Sum of 3 Non-Overlapping Subarrays | ArrayDynamic ProgrammingSliding Window+1 | Hard |
| 691 | Stickers to Spell Word | ArrayHash TableString+5 | Hard |
| 699 | Falling Squares | ArraySegment TreeOrdered Set | Hard |
| 710 | Random Pick with Blacklist | ArrayHash TableMath+3 | Hard |
| 715 | Range Module | DesignSegment TreeOrdered Set | Hard |
| 719 | Find K-th Smallest Pair Distance | ArrayTwo PointersBinary Search+1 | Hard |