Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.

Example:

Input: s = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: the subarray [4,3] has the minimal length under the problem constraint.

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

class Solution {
    public int minSubArrayLen(int s, int[] nums) {
        int windowSum = 0, start = 0, end = 0;
        int minLen = Integer.MAX_VALUE;
        while (end < nums.length) {
            windowSum += nums[end];
            if (windowSum >= s) {
                while (start <= end && windowSum - nums[start] >= s) {
                    windowSum -= nums[start];
                    start++;
                }
                minLen = Math.min(minLen, end - start + 1);
                windowSum -= nums[start];
                start++;
            }
            end++;
        }
        return minLen == Integer.MAX_VALUE ? 0 : minLen;
    }
}