LeetCode 209. Minimum Size Subarray Sum

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 is not one, return 0 instead.

For example, given the array [2,3,1,2,4,3] and s = 7,
the subarray [4,3] has the minimal length under the problem constraint.

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

分析:sum为前i个数的和,长度比nums多一个,sum[0] = 0。这样从0开始一直到len,遍历sum计算sum[j]与sum[i]的差大于等于s的时候的j-i长度,把它与minlen比较,如果比minlen小就更新minlen。
一开始minlen的初始化值是len + 1,如果最后minlen的值仍旧为len + 1,说明没有找到这样的minlen满足题意。则直接返回0;否则返回minlen的值~~