leetcode.209. Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the minimal length of a 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.

class Solution {public:    int minSubArrayLen(int s, vector<int>& nums) {        if(nums.size()==0||s<0)            return 0;                    int start = 0;        int end = 0;                int sum = 0;        int len = INT_MAX;                while(start<nums.size() && end<nums.size()) {              while(sum<s && end<nums.size()) {                  sum += nums[end++];              }              while(sum>=s && start<=end) {                  len = min(len,end-start);                sum -= nums[start++];             }        }                return len == INT_MAX ? 0 : len;            }};