[LC] 1099. Two Sum Less Than K

Given an array A of integers and integer K, return the maximum S such that there exists i < j with A[i] + A[j] = S and S < K. If no i, j exist satisfying this equation, return -1.

Example 1:

Input: A = [34,23,1,24,75,33,54,8], K = 60
Output: 58
Explanation: 
We can use 34 and 24 to sum 58 which is less than 60.

Example 2:

Input: A = [10,20,30], K = 15
Output: -1
Explanation: 
In this case it's not possible to get a pair sum less that 15.

Note:

1. 1 <= A.length <= 100
2. 1 <= A[i] <= 1000
3. 1 <= K <= 2000

class Solution {
    public int twoSumLessThanK(int[] A, int K) {
        if (A == null || A.length == 0) {
            return -1;
        }
        Arrays.sort(A);
        int start = 0, end = A.length - 1;
        int res = -1;
        while (start < end) {
            if (A[start] + A[end] >= K) {
                end -= 1;
            } else {
                res = Math.max(res, A[start] + A[end]);
                start += 1;
            }
        }
        return res;
    }
}