最小的子数字的和 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.

Example: 

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

class Solution {

public:
    int minSubArrayLen(int s, vector<int>& nums) {
     
        int i=0,j=0,sum=0;  // 通过滑动窗口的方式
        int res=INT_MAX;
        
        for(;i<nums.size();++i){
            sum+=nums[i];
            while(sum>=s){
                res=min(res,i-j+1);
                sum-=nums[j++];
            }
        }
        
        return res==INT_MAX?0:res;
    }
};