| 146 | LRU Cache | Hard |
| 155 | Min Stack | Easy |
| 173 | Binary Search Tree Iterator | Medium |
| 208 | Implement Trie (Prefix Tree) | Medium |
| 211 | Design Add and Search Words Data Structure | Medium |
| 225 | Implement Stack using Queues | Easy |
| 232 | Implement Queue using Stacks | Easy |
| 284 | Peeking Iterator | Medium |
| 295 | Find Median from Data Stream | Hard |
| 297 | Serialize and Deserialize Binary Tree | Hard |
| 303 | Range Sum Query - Immutable | Easy |
| 304 | Range Sum Query 2D - Immutable | Medium |
| 307 | Range Sum Query - Mutable | Medium |
| 341 | Flatten Nested List Iterator | Medium |
| 352 | Data Stream as Disjoint Intervals | Hard |
| 355 | Design Twitter | Medium |
| 380 | Insert Delete GetRandom O(1) | Medium |
| 381 | Insert Delete GetRandom O(1) - Duplicates allowed | Hard |
| 432 | All O`one Data Structure | Hard |
| 449 | Serialize and Deserialize BST | Medium |
| 460 | LFU Cache | Hard |
| 535 | Encode and Decode TinyURL | Medium |
| 622 | Design Circular Queue | Medium |
| 641 | Design Circular Deque | Medium |
| 676 | Implement Magic Dictionary | Medium |
| 677 | Map Sum Pairs | Medium |
| 703 | Kth Largest Element in a Stream | Easy |
| 705 | Design HashSet | Easy |
| 706 | Design HashMap | Easy |
| 707 | Design Linked List | Medium |