LeetCode 209. Minimum Size Subarray Sum

class Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        // remain a range whose sum<s
        int start=0, end;
        int sum=0, res=INT_MAX;
        for (end=0;end<nums.size();++end){
            sum += nums[end];
            while (sum>=s){
                res = min(res,end-start+1);
                sum -= nums[start++];
            }
        }
        return res==INT_MAX?0:res;
    }
};