[LeetCode] Minimum Size Subarray Sum

Given an array ofnpositive integers and a positive integers, 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]ands = 7,the subarray[4,3]has the minimal length under the PRoblem constraint.

这道题主要还是先要把题目的要求弄清楚。首先题目中所说的if there is not one, return 0 instead。怎样才算是没有呢？

这里意思是如果我们算出来的min length和array本身的长度一样，那么我们就应该return 0。

这里比较容易想到的是用two pointer来计算。一个pointer用来计算sum，和另一个pointer紧随其后，用来判断长度。

代码如下。~

public class Solution {    public int minSubArrayLen(int s, int[] nums) {        //two pointer         //one from start;one follows        int start = 0;          int end = 0;                    int sum = 0;          int min = nums.length;                    while(start<nums.length && end<nums.length) {              while(sum<s && end<nums.length) {                  sum=sum+nums[end];                end++;            }              while(sum>=s && start<=end) {                  min = Math.min(min, end-start);                  sum =sum-nums[start];                start++;            }          }          if(min==nums.length){            return 0;        }        return min;    }}