209. Minimum Size Subarray Sum

209。Minimum Size Subarray Sum

Given an array of positive integers nums and a positive integer target, return the minimal length of a

subarray whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.

Example 1:

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

Example 2:

Input: target = 4, nums = [1,4,4]
Output: 1

Example 3:

Input: target = 11, nums = [1,1,1,1,1,1,1,1]
Output: 0

Constraints:

• 1 <= target <= 109

• 1 <= nums.length <= 105

• 1 <= nums[i] <= 104

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)).

My Solutions：

class Solution {
    public int minSubArrayLen(int target, int[] nums) {
        int min = nums.length; 
        boolean existsMin = false;
        int l = 0, sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            while (sum >= target) {
                min = Math.min(min, i - l + 1);
                existsMin = true;
                sum -= nums[l];
                l++;
            }
        }

        return existsMin ? min : 0;
    }
}