| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 121 | Dutch National Flag | Medium | ArraysArrayPartitioning |
| 122 | Temperature Tracker | Medium | ArraysArrayStack |
| 123 | Sparse Matrix Operations | Medium | Arrays2D ArrayOptimization |
| 124 | Time Slot Scheduler | Medium | ArraysArraySorting |
| 125 | Building Shadow Calculator | Medium | ArraysArrayLogic |
| 126 | Singly Linked List | Medium | Linked ListsLinked ListPointers |
| 127 | Doubly Linked List | Medium | Linked ListsLinked ListPointers |
| 128 | Linked List Partitioner | Medium | Linked ListsLinked ListPointers |
| 129 | Linked List Intersection Finder | Medium | Linked ListsLinked ListTwo Pointers |
| 130 | Linked List Sorter | Medium | Linked ListsLinked ListMerge Sort |
| 131 | MFU Cache Implementation | Medium | Linked ListsLinked ListHashMap |
| 132 | Polynomial Addition | Medium | Linked ListsLinked ListMath |
| 133 | Linked List Group Reverser | Medium | Linked ListsLinked ListLogic |
| 134 | Skip List Implementation | Medium | Linked ListsLinked ListProbability |
| 135 | Linked List Zipper | Medium | Linked ListsLinked ListReorder |
| 136 | Binary Search Tree | Medium | TreesBSTRecursion |
| 137 | Tree Height and Depth | Medium | TreesBinary TreeRecursion |
| 138 | Level Order Traversal | Medium | TreesBinary TreeQueue |
| 139 | BST to Balanced BST | Medium | TreesBSTArray |
| 140 | Tree Boundary Traversal | Medium | TreesBinary TreeTraversal |