209. 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.
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.

click to show more practice.
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.

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** 解题思路 **
Two pointers, O(n) Time complexity

/**
     * @param nums: an array of integers
     * @param s: an integer
     * @return: an integer representing the minimum size of subarray
     */
    public int minimumSize(int[] nums, int s) {
        if (nums == null || nums.length == 0) return -1;
        
        int i = 0, j = 0, sum = 0, min = Integer.MAX_VALUE;
        
        while (j < nums.length) {
            if (sum < s && j < nums.length) {        
              sum += nums[j++];
            }
            while (sum >=s ) {
                min = Math.min(min, j - i);
                sum -= nums[i++];
            }
        }
        return min == Integer.MAX_VALUE ? -1 : min;
    }