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    // Complexity - O(nlogn)
    private int[] findPair_2(int[] A) {
        Arrays.sort(A); // O(nlogn)
        for (int i = 0, l = A.length; i < l; i++) { //O(nlogn)
            int j = Arrays.binarySearch(A, i + 1, l, -A[i]);
            if (j > i) return new int[]{A[i], A[j]};
        }
        return null;
    }