209. Minimum Size Subarray Sum

 双指针，start和end之间维护一段>=s的数列，

class Solution {public:    int minSubArrayLen(int s, vector<int>& nums) {        int n=nums.size();        int sum=0,start=0,end=0;        int m=n+1;        while(end<n)        {            while(end<n&&sum<s)            {                sum+=nums[end++];            }            while(sum>=s&&start<=end)            {                m=min(end-start,m);                sum-=nums[start++];            }        }        if(m==n+1)            return 0;        return m;    }};