class Solution {
public:
int minSubArrayLen(int target, std::vector<int>& nums) {
int fast = 0, slow = 0, sum = 0, windowlen = 0, res=nums.size()+1;
for (;fast < nums.size();fast++){
sum += nums[fast];
while (sum >= target){
windowlen = fast -slow+1;
res = res < windowlen ? res :windowlen;
sum -= nums[slow++];
}
}
return res==nums.size()+1 ?0:res;
}
};