Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.
1 ≤ target ≤ 10⁹1 ≤ nums.length ≤ 10⁵1 ≤ nums[i] ≤ 10⁴Use two pointers to define a window.
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