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.

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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.

Solution

public class Solution {
 public int minSubArrayLen(int s, int[] nums) {
        if (nums == null || nums.length == 0) return 0;

        int left = 0;
        int right = 0;
        int sum = nums[0];
        int result = Integer.MAX_VALUE;
        boolean flag = false;
        while (right < nums.length) {
            if (sum >= s) {
                if (right == left) {
                    return 1;
                }

                result = Math.min(right - left + 1, result);
                flag = true;
                sum -= nums[left];
                left++;
            } else {
                right++;

                if (right < nums.length) {
                    sum += nums[right];
                }
            }
        }

        if (flag) {
            return result;
        } else {
            return 0;
        }
    }
}