Minimum Size Subarray Sum

Source

• lintcode: Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the
minimal length of a subarray of which the sum ≥ s. If there isn't one,
return -1 instead.

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.

Challenge
If you have figured out the O(n) solution, try coding another solution of
which the time complexity is O(n log n).

Java

public class Solution {
    /**
     * @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 start=0;
        int end = 0;
        int sum = 0;
        int min = Integer.MAX_VALUE;

        while (end<nums.length){
            sum+=nums[end++];

            while(sum>=s) {
                min = Math.min(min, end-start);
                sum -= nums[start++];
            }
        }

        return min == Integer.MAX_VALUE ? -1 : min;
    }
}