Sliding Window Maximum
Given an array nums and a sliding window of size k Return an array of the maximum value in each window position Example: nums = [1,3,-1,-3,5,3,6,7], k = 3 => [3,3,5,5,6,7] Use a deque (double-ended queue) for O(n) time complexity
This problem is a great test of whether you can keep window state consistent as it moves. It's a hard one for a reason: it stresses stateful scanning when the rules pile up. Be disciplined about counts and boundaries; most bugs are off-by-one window moves.
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