LeetCode 209. Minimum Size Subarray Sum--从数组中查找某个最短子段的和大于等于s时，返回子段的长度，反之返回0

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.

Example: 

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

Follow up:

If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n). 

public class LeetCode_209_MinimumS