Leetcode209 subarray with the smallest length

Given a containing  n  An array of positive integers and a positive integer target .

Find the sum of the array ≥ target The smallest length of Continuous subarray  [numsl, numsl+1, ..., numsr-1, numsr] , And return its length . If there is no sub array that meets the conditions , return 0 .

The sliding window ：

Define two pointers start and end Each represents a subarray （ Sliding window ） Start and end positions of , Maintenance variables sum Stores the elements and in the subarray nums[start] To nums[end] Elements and .

In the initial state ,start and end All point to subscripts 0,sum The value of is 0.

Every iteration , take nums[end] Add to sum, If sum≥s, Then update the minimum length of the subarray （ At this point, the length of the subarray is end−start+1）, And then nums[start] from sum Subtract from and start Move right , until sum<s, In this process, the minimum length of the subarray is also updated . At the end of each iteration , take end Move right .

public int minSubArrayLen(int target, int[] nums) {
    int start = 0;
    int len = Integer.MAX_VALUE;
    int sum = 0;
    for(int end = 0; end < nums.length; end++){
        sum += nums[right];
        while(sum >= target){
            len = Math.min(len,end-start+1);
            sum -= nums[start++];
            }
        }
    return len == Integer.MAX_VALUE ? 0 : len;
}