Minimum_Size_Subarray_Sum.java

/*

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)). */


class Solution {
    public int minSubArrayLen(int target, int[] nums) {
        int low =0;
        int sum = 0;
        int n = nums.length;
        int result = Integer.MAX_VALUE;
        for (int high = 0 ; high <n ; high ++){
            sum += nums[high];

            while(sum >= target){
                result = Math.min(result,(high-low+1));
                sum -= nums[low];
                low ++;
            }
        }
        return result == Integer.MAX_VALUE ? 0 : result;
        
    }
}