| Problem | Difficulty |
|---|---|
| 844. Backspace String Compare | Easy (1227) |
| 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) |
| 71. Simplify Path | Medium |
| @@636. Exclusive Time of Functions | Medium |
My contest https://leetcode.com/problems/find-mirror-score-of-a-string/description/ 1578
https://leetcode.com/problems/maximum-frequency-stack/description/ h 2027
Solved: https://leetcode.com/problems/build-an-array-with-stack-operations/description/ 1180
Solved: https://leetcode.com/problems/design-a-stack-with-increment-operation/description/ 1285 // Using array + top pointer to simulate stack, should have very clear definition of the top pointer. 2024/10/21
Solved: https://leetcode.com/problems/baseball-game/description/ // To get previous elements, use stack. 2024/10/21
Solved: https://leetcode.com/problems/removing-stars-from-a-string/description/ 1347 // Very easy problem, mind the edge case. 2024/10/21
| Problem | Difficulty |
|---|---|
| 150. Evaluate Reverse Polish Notation | Medium |
| @@1190. Reverse Substrings Between Each Pair of Parentheses | Medium (1485) |
| 394. Decode String | Medium |
| @@856. Score of Parentheses | Medium (1562) |
| 1106. Parsing A Boolean Expression | Hard (1880) |
| @@227. Basic Calculator II | Medium |
| @@224. Basic Calculator | Hard |
| Problem | Difficulty |
|---|---|
| 20. Valid Parentheses | Easy |
| 1614. Maximum Nesting Depth of the Parentheses | Easy (1322) |
| @@1021. Remove Outermost Parentheses | Easy (1311) |
| @@921. Minimum Add to Make Parentheses Valid | Medium (1242) |
| 1249. Minimum Remove to Make Valid Parentheses | Medium (1657) |
| @@1541. Minimum Insertions to Balance a Parentheses String | Medium (1759) |
| @@678. Valid Parenthesis String | Medium (1700) |
| @@1963. Minimum Number of Swaps to Make the String Balanced | Medium (1688) |
| Problem | Difficulty |
|---|---|
| 735. Asteroid Collision | Medium |
| 1047. Remove All Adjacent Duplicates In String | Easy (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/minimum-deletions-to-make-array-beautiful/description/ 1510
- https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string-ii/description/ 1541
- https://leetcode.com/problems/maximum-score-from-removing-substrings/description/ 1868
- https://leetcode.com/problems/robot-collisions/description/ 2091
- Solved: https://leetcode.com/problems/minimum-string-length-after-removing-substrings 1282 // Easy to solve by stack and learned two pointers approach, 2024/10/30
| Problem | Difficulty |
|---|---|
| 739. Daily Temperatures | Medium |
| 496. Next Greater Element I | Easy |
| 503. Next Greater Element II | Medium |
| 901. Online Stock Span | Medium (1709) |
| Problem | Difficulty |
|---|
- https://leetcode.com/problems/next-greater-node-in-linked-list/ 1570
- https://leetcode.com/problems/maximum-width-ramp/description/ 1607
- https://leetcode.com/problems/longest-well-performing-interval/description/ 1908
- https://leetcode.com/problems/132-pattern/ 2000
- TODO: 2866. Beautiful Towers II 2071
| Problem | Difficulty |
|---|---|
| 42. Trapping Rain Water | Hard |
| 84. Largest Rectangle in Histogram | Hard |
| 85. Maximal Rectangle | Hard |
| Problem | Difficulty |
|---|---|
| 907. Sum of Subarray Minimums | Medium (1976) |
| 2104. Sum of Subarray Ranges | Medium (2000) |
| Problem | Difficulty |
|---|---|
| 402. Remove K Digits | Medium (1800) |
| 316. Remove Duplicate Letters | Medium (2184?) |
| 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/ 1610
| Problem | Difficulty |
|---|---|
| 239. Sliding Window Maximum | Hard |
- 155. Min Stack
- 946. Validate Stack Sequences
- 636. Exclusive Time of Functions
- 150. Evaluate Reverse Polish Notation
- 394. Decode String
- 856. Score of Parentheses
- 1106. Parsing A Boolean Expression
- 227. Basic Calculator II
- 224. Basic Calculator
- 921. Minimum Add to Make Parentheses Valid
- 1249. Minimum Remove to Make Valid Parentheses
- 1541. Minimum Insertions to Balance a Parentheses String
- 678. Valid Parenthesis String
- 1963. Minimum Number of Swaps to Make the String Balanced
- 735. Asteroid Collision
- 239. Sliding Window Maximum
TODO: Add more explanation videos for monotonous stack.