Leetcode 题目解析之 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.

More practice:

If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n).

定义两个指针，st和ed。如果sum>=s，sum从前面元素开始减；如果sum< s，ed++。

   public int minSubArrayLen(int s, int[] nums) {
        int sum = 0;
        int st = 0;
        int min = Integer.MAX_VALUE;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (sum >= s) {
                while (sum - nums[st] >= s) {
                    sum -= nums[st++];
                }
                min = Math.min(min, i - st + 1);
            }
        }
        if (min > nums.length) {
            return 0;
        }
        return min;
    }