209

class Solution {
public:
    int minSubArrayLen(int target, vector<int>& nums) {
        int left, right, ans, sum, n=nums.size();
        ans = n+1;

        for(left=0, right=0, sum=0; right<n; right++){
            sum += nums[right];
            if(sum >= target) ans = min(ans, right+1);

            while(sum-nums[left] >= target){
                sum -= nums[left++];
                ans = min(ans, right-left+1);
            }
        }
        if(ans == n+1) ans = 0;
        return ans;
    }
};