Minimum Size Subarray Sum

题目
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.

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).

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

答案

    public int minSubArrayLen(int s, int[] nums) {
        if(nums.length == 0) return 0;
        int sub_sum = nums[0];
        int left = 0, right = 0, min = Integer.MAX_VALUE;
        while(right < nums.length) {
            if(sub_sum >= s) {
                min = Math.min(min, right - left + 1);
                sub_sum -= nums[left];
                if(right == left) right++;
                left++;
            }
            else {
                right++;
                if(right < nums.length)
                    sub_sum += nums[right];
            }
        }
        return (min == Integer.MAX_VALUE)? 0 : min;
    }