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 isn't 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.click to show more practice.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).两指针问题，动态决定前后指针的位置*/class Solution {public:    int minSubArrayLen(int s, vector<int>& nums) {        int sum=0,start=0,end=0,minLen=INT_MAX;        while(end< nums.size())        {            sum+=nums[end++];            while(sum>=s)            {                minLen = min(minLen,end-start);                sum-=nums[start++];            }        }        return minLen==INT_MAX ? 0 : minLen;    }};