Stacks
25 problems — 6 easy, 16 medium, 3 hard.
| # | Title | Difficulty | Frequency |
|---|---|---|---|
| 20 | Valid Parentheses | easy | foundational |
| 22 | Generate Parentheses | medium | frequently asked |
| 42 | Trapping Rain Water | hard | foundational |
| 71 | Simplify Path | medium | frequently asked |
| 84 | Largest Rectangle in Histogram | hard | company favorite |
| 150 | Evaluate Reverse Polish Notation | medium | frequently asked |
| 155 | Min Stack | medium | frequently asked |
| 232 | Implement Queue using Stacks | easy | frequently asked |
| 394 | Decode String | medium | frequently asked |
| 402 | Remove K Digits | medium | frequently asked |
| 456 | 132 Pattern | medium | frequently asked |
| 496 | Next Greater Element I | easy | foundational |
| 503 | Next Greater Element II | medium | frequently asked |
| 682 | Baseball Game | easy | occasionally asked |
| 735 | Asteroid Collision | medium | frequently asked |
| 739 | Daily Temperatures | medium | frequently asked |
| 844 | Backspace String Compare | easy | frequently asked |
| 853 | Car Fleet | medium | less common |
| 856 | Score of Parentheses | medium | frequently asked |
| 895 | Maximum Frequency Stack | hard | less common |
| 901 | Online Stock Span | medium | frequently asked |
| 921 | Minimum Add to Make Parentheses Valid | medium | frequently asked |
| 946 | Validate Stack Sequences | medium | frequently asked |
| 1047 | Remove All Adjacent Duplicates In String | easy | frequently asked |
| 2390 | Removing Stars From a String | medium | occasionally asked |