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.

click to show more practice.

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

 1 public class Solution {
 2     public int minSubArrayLen(int s, int[] nums) {
 3         if(nums == null || nums.length == 0) return 0;
 4         int b = 0,e = 0,minlen = Integer.MAX_VALUE,sum = 0;
 5         while(e < nums.length){
 6             sum += nums[e++];
 7             while(sum >= s){
 8                 minlen = Math.min(minlen,e-b);
 9                 sum -= nums[b++];
10             }
11         }
12         return minlen == Integer.MAX_VALUE ? 0:minlen;
13     }
14 }

用两个指针，begin， end从前往后遍历。