209. Minimum Size Subarray Sum java solutions

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.

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Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

public class Solution {
    public int minSubArrayLen(int s, int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        int b = 0,e = 0,minlen = Integer.MAX_VALUE,sum = 0;
        while(e < nums.length){
            sum += nums[e++];
            while(sum >= s){
                minlen = Math.min(minlen,e-b);
                sum -= nums[b++];
            }
        }
        return minlen == Integer.MAX_VALUE ? 0:minlen;
    }
}

用两个指针，begin， end从前往后遍历。