[LeetCode] 209. Minimum Size Subarray Sum (Easy version LC 862)

Problem

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.

Example:

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

Solution

class Solution {
    public int minSubArrayLen(int target, int[] nums) {
        if (nums == null || nums.length == 0) return 0;
        int i = 0, j = 0, sum = 0, min = Integer.MAX_VALUE;
        
        while (i <= j && j < nums.length) {
            sum += nums[j];
            while (sum >= target && i <= j) {
                min = Math.min(min, j-i+1);
                sum -= nums[i];
                i++;
            }
            j++;
        }
        
        return min == Integer.MAX_VALUE ? 0 : min;
    }
}