KMS_studio programming KMS_studio programming

Life/PS

• [LeetCode] 42. Trapping Rain Water

  Life/PS 2026. 5. 27. 17:17

  At the point k, the height of the water surface is min(max(h[1...k]), max(h[k+1...])).

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• [LeetCode] 41. First Missing Positive

  Life/PS 2026. 5. 24. 14:24

  Naive approach to solve this problem is using hashmap.However, we can use the fact that the answer must lower that len(nums)+1.

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• [LeetCode] 32. Longest Valid Parentheses

  Life/PS 2026. 5. 23. 13:34

  It is well known that stack-based approaches are commonly used for parenthesis matching problems. However, for this problem, a different approach is also possible.

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• [LeetCode] 25. Reverse Nodes in k-Group

  Life/PS 2026. 5. 22. 23:57

  The code will destruct the parameter head. So, this code will not operate properly in real situation.

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• [LeetCode] 30. Substring with Concatenation of All Words

  Life/PS 2026. 5. 22. 00:37

  We can use hashmap (unordered_map in STL) since all of strings in words have precise length k.

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• [LeetCode] 23. Merge k Sorted Lists

  Life/PS 2026. 5. 18. 16:43

  Pick up the smallest element among k lists. Repeat this untill all elements are used.You should know that this code DESTRUCT the parameter vector& lists.

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• [LeetCode] 10. Regular Expression Matching

  Life/PS 2026. 5. 15. 13:53

  Considering a recursive solution. The helper function determines whether s[s_idx:] and p[p_idx:] match. One might worry about a time limit exceeded issue , but since the length is very short, at most 20, it passes within about 500 ms. With memoization, it passes in 0 ms at the cost of using about 10 MB of memory.

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• [LeetCode] 4. Median of Two Sorted Arrays

  Life/PS 2026. 5. 14. 13:07

  If you have studied CLRS, you may come up with a similar idea. As a side note, it does not have to be the median; you can find the t-th element of the concatenated array in $O(\log⁡(n+m))$ time.

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