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.

Solution:

public class Solution {
    public int minSubArrayLen(int s, int[] nums) {
        int slow=0, fast=0, sum=0, ans=Integer.MAX_VALUE;
        while(fast<nums.length){
            while(sum<s && fast<nums.length) sum += nums[fast++];
            while(sum>=s && slow<fast){
                ans = Math.min(ans, fast-slow);
                sum -= nums[slow++];
            } 
        }
        return ans==Integer.MAX_VALUE ? 0 : ans;
    }
}