Problem

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.

Examples

Example 1:

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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:

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

Solution

Method 1 - Using Sorting and Two Pointers

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public int twoSumLessThanK(int[] A, int K) {
	Arrays.sort(A);
	int i = 0;
	int j = A.length - 1;
	int ans = -1;
	while (i < j) {
		if (A[i] + A[j] >= K) {
			j--;
		} else {
			ans = Math.max(ans, A[i] + A[j]);
			i++;
		}
	}
	return ans;
}