I Problem

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.

Example 1:
Input: target = 7, nums = [2, 3, 1, 2, 4, 3]
Output: 2
Explanation: The subarray [4, 3] has the minimal length under the problem constraint.