Generated by Codex with GPT-5
MEDIUMArray, BacktrackingThe input contains distinct integers, and the task is to return every possible ordering of those integers.
That means the algorithm is not trying to find one best answer. It is trying to systematically explore a decision tree where:
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MEDIUMArray, Math, MatrixThe input is an n x n matrix, and the task is to rotate it 90 degrees clockwise.
The important constraint is that the rotation must happen in place. That means the matrix itself must be rearranged without allocating another full n x n matrix for the final answer.
Generated by Codex with GPT-5
MEDIUMString, Dynamic ProgrammingTwo strings are given, word1 and word2.
The goal is to transform word1 into word2 using as few operations as possible. The allowed operations are:
This is not a greedy string-matching problem. A locally good edit can make the rest of the string worse, so the real challenge is deciding which prefixes of the two words should be matched together.
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MEDIUMArray, Two Pointers, SortingThe input array contains only 0, 1, and 2. Those values represent three categories, and the goal is to reorder the array in place so all 0s come first, then all 1s, then all 2s.
Generated by Codex with GPT-5
HARDArray, BacktrackingThe board details can make this problem look more complicated than it is.
At a higher level, the task is:
That “one queen per row” reframing is the key simplification.
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MEDIUMArray, Dynamic ProgrammingEach house has some amount of money. The thief wants the largest total possible, but robbing two neighboring houses triggers the alarm.
So the real question is:
At every house, is it better to:
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MEDIUMString, Dynamic Programming, BacktrackingGiven n pairs of parentheses, generate every string that is:
2n characters long( and )The last condition is the important one.
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MEDIUMArray, Binary SearchThe array started out sorted in ascending order, then got rotated at some pivot.
That means a sequence like [0, 1, 2, 4, 5, 6, 7] might become [4, 5, 6, 7, 0, 1, 2].
Generated by Codex with GPT-5
MEDIUMArray, Binary SearchThe input array is sorted, and the target value may appear many times in one contiguous block.
The task is not just to decide whether the target exists. It is to return the exact starting and ending indices of that block.
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MEDIUMArray, Hash Table, String, SortingTwo strings belong in the same group if they use the exact same letters with the exact same counts, just in a different order.
So the problem is not really about comparing every string against every other string. It is about finding a stable “signature” for each word, so all words with the same signature land in the same bucket.
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