| 4 | Median Of Two Sorted Arrays | Array | Hard |
| 10 | Regular Expression Matching | String | Hard |
| 25 | Reverse Nodes In K Group | Linked List | Hard |
| 30 | Substring With Concatenation Of All Words | String | Hard |
| 37 | Sudoku Solver | Array | Hard |
| 51 | N Queens | Array | Hard |
| 174 | Dungeon Game | Array | Hard |
| 214 | Shortest Palindrome | String | Hard |
| 218 | The Skyline Problem | Array | Hard |
| 224 | Basic Calculator | Math | Hard |
| 239 | Sliding Window Maximum | Array | Hard |
| 282 | Expression Add Operators | Math | Hard |
| 297 | Serialize And Deserialize Binary Tree | Tree | Hard |
| 312 | Burst Balloons | Array | Hard |
| 327 | Count Of Range Sum | Array | Hard |
| 407 | Trapping Rain Water Ii | Array | Hard |
| 410 | Split Array Largest Sum | Array | Hard |
| 432 | All Oone Data Structure | Design | Hard |
| 446 | Arithmetic Slices Ii Subsequence | Array | Hard |
| 460 | Lfu Cache | Design | Hard |
| 480 | Sliding Window Median | Array | Hard |
| 679 | 24 Game | Array | Hard |
| 685 | Redundant Connection Ii | Depth-First Search | Hard |
| 689 | Maximum Sum Of 3 Non Overlapping Subarrays | Array | Hard |
| 691 | Stickers To Spell Word | Array | Hard |
| 699 | Falling Squares | Array | Hard |
| 719 | Find K Th Smallest Pair Distance | Array | Hard |
| 746 | Prefix And Suffix Search | Array | Hard |
| 759 | Set Intersection Size At Least Two | Array | Hard |
| 779 | Max Chunks To Make Sorted Ii | Array | Hard |
| 794 | Swim In Rising Water | Depth-First Search | Hard |
| 819 | Minimum Swaps To Make Sequences Increasing | Array | Hard |
| 833 | Bus Routes | Array | Hard |
| 854 | Making A Large Island | Depth-First Search | Hard |
| 855 | Count Unique Characters Of All Substrings Of A Given String | String | Hard |
| 892 | Shortest Subarray With Sum At Least K | Array | Hard |
| 902 | Minimum Number Of Refueling Stops | Array | Hard |
| 918 | Reachable Nodes In Subdivided Graph | Heap (Priority Queue) | Hard |
| 989 | Largest Component Size By Common Factor | Array | Hard |
| 1000 | Delete Columns To Make Sorted Iii | Array | Hard |
| 1042 | Minimum Cost To Merge Stones | Array | Hard |
| 1093 | Recover A Tree From Preorder Traversal | Tree | Hard |
| 1145 | Number Of Submatrices That Sum To Target | Array | Hard |
| 1170 | Shortest Common Supersequence | String | Hard |
| 1197 | Parsing A Boolean Expression | String | Hard |
| 1234 | Number Of Paths With Max Score | Array | Hard |
| 1262 | Online Majority Element In Subarray | Array | Hard |
| 1337 | Design Skiplist | Design | Hard |
| 1352 | Maximum Profit In Job Scheduling | Array | Hard |
| 1409 | Minimum Number Of Flips To Convert Binary Matrix To Zero Matrix | Array | Hard |
| 1414 | Shortest Path In A Grid With Obstacles Elimination | Array | Hard |
| 1485 | Minimum Cost To Make At Least One Valid Path In A Grid | Array | Hard |
| 1508 | Longest Happy Prefix | String | Hard |
| 1550 | Find The Kth Smallest Sum Of A Matrix With Sorted Rows | Array | Hard |
| 1676 | Minimum Number Of Days To Eat N Oranges | Dynamic Programming | Hard |
| 1740 | Count Subtrees With Max Distance Between Cities | Tree | Hard |
| 1744 | Number Of Ways To Form A Target String Given A Dictionary | Array | Hard |
| 1766 | Minimum Number Of Removals To Make Mountain Array | Array | Hard |
| 1772 | Create Sorted Array Through Instructions | Array | Hard |
| 1851 | Maximum Number Of Events That Can Be Attended Ii | Array | Hard |
| 1871 | Palindrome Partitioning Iv | String | Hard |
| 1897 | Maximize Palindrome Length From Subsequences | String | Hard |
| 1953 | Finding Mk Average | Design | Hard |
| 2023 | Design Movie Rental System | Array | Hard |
| 2131 | Smallest Missing Genetic Value In Each Subtree | Tree | Hard |
| 2140 | Longest Subsequence Repeated K Times | String | Hard |
| 2150 | Kth Smallest Product Of Two Sorted Arrays | Array | Hard |
| 2162 | Partition Array Into Two Arrays To Minimize Sum Difference | Array | Hard |
| 2176 | Parallel Courses Iii | Array | Hard |
| 2180 | Maximum Number Of Tasks You Can Assign | Array | Hard |
| 2198 | Process Restricted Friend Requests | Union Find | Hard |
| 2201 | Valid Arrangement Of Pairs | Depth-First Search | Hard |
| 2213 | Find All People With Secret | Depth-First Search | Hard |
| 2229 | Maximum Fruits Harvested After At Most K Steps | Array | Hard |
| 2246 | Maximum Employees To Be Invited To A Meeting | Depth-First Search | Hard |
| 2275 | Find Substring With Given Hash Value | String | Hard |
| 2307 | Replace Non Coprime Numbers In Array | Array | Hard |
| 2311 | Minimum White Tiles After Covering With Carpets | String | Hard |
| 2375 | Minimum Obstacle Removal To Reach Corner | Array | Hard |
| 2389 | Design A Text Editor | String | Hard |
| 2394 | Count Subarrays With Score Less Than K | Array | Hard |
| 2449 | Maximum Number Of Robots Within Budget | Array | Hard |
| 2479 | Meeting Rooms Iii | Array | Hard |
| 2494 | Sum Of Prefix Scores Of Strings | Array | Hard |
| 2513 | Number Of Pairs Satisfying Inequality | Array | Hard |
| 2527 | Count Subarrays With Fixed Bounds | Array | Hard |
| 2531 | Create Components With Same Value | Tree | Hard |
| 2545 | Height Of Binary Tree After Subtree Removal Queries | Tree | Hard |
| 2554 | Minimum Total Distance Traveled | Array | Hard |
| 2583 | Divide Nodes Into The Maximum Number Of Groups | Breadth-First Search | Hard |
| 2588 | Maximum Number Of Points From Grid Queries | Array | Hard |
| 2601 | Number Of Great Partitions | Array | Hard |
| 2681 | Put Marbles In Bags | Array | Hard |
| 2689 | Rearranging Fruits | Array | Hard |
| 2711 | Minimum Time To Visit A Cell In A Grid | Array | Hard |
| 2839 | Maximum Sum Queries | Array | Hard |
| 3058 | Maximum Number Of K Divisible Components | Tree | Hard |
| 3181 | Find Building Where Alice And Bob Can Meet | Array | Hard |
| 3217 | Number Of Possible Sets Of Closing Branches | Heap (Priority Queue) | Hard |
| 3218 | Find Number Of Coins To Place In Tree Nodes | Tree | Hard |
| 3307 | Find The Maximum Sum Of Node Values | Tree | Hard |
| 3348 | Minimum Cost Walk In Weighted Graph | Array | Hard |
| 3439 | Find Minimum Diameter After Merging Two Trees | Tree | Hard |
| 3459 | Find The Minimum Area To Cover All Ones Ii | Array | Hard |
| 3466 | Number Of Subarrays With And Value Of K | Array | Hard |
| 3592 | Find X Sum Of All K Long Subarrays Ii | Array | Hard |
| 3601 | Find The K Th Character In String Game Ii | Math | Hard |
| 3640 | Maximum Frequency Of An Element After Performing Operations Ii | Array | Hard |
| 3645 | Maximize The Number Of Target Nodes After Connecting Trees Ii | Tree | Hard |
| 3648 | Find The Maximum Number Of Fruits Collected | Array | Hard |
| 3682 | Count The Number Of Arrays With K Matching Adjacent Elements | Math | Hard |
| 3733 | Length Of Longest V Shaped Diagonal Segment | Array | Hard |
| 3853 | Minimum Weighted Subgraph With The Required Paths Ii | Tree | Hard |
| 4035 | Maximum Partition Factor | Depth-First Search | Hard |