[leedcode 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.

public class Solution {
    public int minSubArrayLen(int s, int[] nums) {
        //借助一个指针start，判断从start到i的sum是否大于s，如果大于，start++，并且不断更新minLen
        //注意，一开始需要将minLen初始化为Integer.MAX_VALUE
        int minLen=Integer.MAX_VALUE;
        int start=0;
        int sum=0;
        for(int i=0;i<nums.length;i++){
            sum+=nums[i];
            while(sum>=s){
                minLen=Math.min(minLen,i-start+1);
                sum-=nums[start];
                start++;
                
            }
        }
        return minLen==Integer.MAX_VALUE?0:minLen;
    }
}