| Problem | Difficulty |
|---|---|
| 155. Min Stack | Easy |
| 232. Implement Queue using Stacks | Easy |
| 225. Implement Stack using Queues | Easy |
| 1472. Design Browser History | Medium (1453) |
| 946. Validate Stack Sequences | Medium (1461) |
- https://leetcode.com/problems/build-an-array-with-stack-operations/description/ 1180
- https://leetcode.com/problems/design-a-stack-with-increment-operation/description/ 1285
- https://leetcode.com/problems/baseball-game/description/
- https://leetcode.com/problems/removing-stars-from-a-string/description/ 1347
- https://leetcode.com/problems/simplify-path/description/
- https://leetcode.com/problems/exclusive-time-of-functions/description/ m
- https://leetcode.com/problems/maximum-frequency-stack/description/ h 2027
| Problem | Difficulty |
|---|---|
| 20. Valid Parentheses | Easy |
| 921. Minimum Add to Make Parentheses Valid | Medium (1242) |
| 1047. Remove All Adjacent Duplicates In String | Easy (1286) |
| 1249. Minimum Remove to Make Valid Parentheses | Medium (1657) |
| 856. Score of Parentheses | Medium (1562) |
| 394. Decode String | Medium |
- https://leetcode.com/problems/remove-outermost-parentheses/description/ 1311
- https://leetcode.com/problems/maximum-nesting-depth-of-the-parentheses/description/ 1322
- https://leetcode.com/problems/reverse-substrings-between-each-pair-of-parentheses/description/ 1485
- https://leetcode.com/problems/reverse-substrings-between-each-pair-of-parentheses/description/ 1688
- https://leetcode.com/problems/minimum-insertions-to-balance-a-parentheses-string/description/ 1759
| Problem | Difficulty |
|---|---|
| 735. Asteroid Collision | Medium |
- https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/description/ 1286
- https://leetcode.com/problems/make-the-string-great/description/ 1344
- https://leetcode.com/problems/check-if-word-is-valid-after-substitutions/description/ 1426
- https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string-ii/description/ 1541
| Problem | Difficulty |
|---|---|
| 150. Evaluate Reverse Polish Notation | Medium |
| 224. Basic Calculator | Hard |
| Problem | Difficulty |
|---|---|
| 496. Next Greater Element I | Easy |
| 503. Next Greater Element II | Medium |
| 739. Daily Temperatures | Medium |
| 901. Online Stock Span | Medium (1709) |
| 402. Remove K Digits | Medium (1800) |
| 42. Trapping Rain Water | Hard |
| 907. Sum of Subarray Minimums | Medium (1976) |
| 2104. Sum of Subarray Ranges | Medium (2000) |
| 316. Remove Duplicate Letters | Medium (2184?) |
| 84. Largest Rectangle in Histogram | Hard |
| 2866. Beautiful Towers II | Medium (2071) |
- https://leetcode.com/problems/final-prices-with-a-special-discount-in-a-shop/description/ 1212
- https://leetcode.com/problems/next-greater-node-in-linked-list/ 1570
- https://leetcode.com/problems/maximum-width-ramp/description/ 1607
- https://leetcode.com/problems/find-the-most-competitive-subsequence/description/ 1802
- https://leetcode.com/problems/longest-well-performing-interval/description/ 1908
- https://leetcode.com/problems/maximum-score-of-a-good-subarray/description/ 1945
- https://leetcode.com/problems/132-pattern/ 2000
- https://leetcode.com/problems/maximum-subarray-min-product/description/ 2051
- https://leetcode.com/problems/maximal-rectangle/description/ h
| Problem | Difficulty |
|---|---|
| 622. Design Circular Queue | Medium |
| 1823. Find the Winner of the Circular Game | Medium |
- https://leetcode.com/problems/number-of-recent-calls/description/ 1337
- https://leetcode.com/problems/reveal-cards-in-increasing-order/description/ 1686
- https://leetcode.com/problems/dota2-senate/description/ m
- https://leetcode.com/problems/design-circular-deque/description/ m
- https://leetcode.com/problems/design-front-middle-back-queue/description/ m
| Problem | Difficulty |
|---|---|
| 239. Sliding Window Maximum | Hard |