Divide and conquer approach to find if sum of any two value a and b is equal to user given input.

App.java

public class App {
    public static void main(String[] args) {
        int x = 8;
        int[] arr = {-3, -2, 1, 7, 8, 11, 12, 21};
        for (int i = 0; i < arr.length; i++) {
            int a = arr[i];
            int b = x - a;
            if (b <= arr[arr.length - 1]) {
                int result = divideAndConquer(arr, b, i + 1, arr.length - 1);
                if (result != -1) {
                    System.out.println("Pair is (a + b) (" + a + " + " + b + ") x = " + x);
                    break;
                }
            }
        }
    }

    private static int divideAndConquer(int[] values, int target, int start, int end) {
        if (start > end) { // Code here means the value does not exist
            return -1;
        }

        int middle = (start + end) / 2;
        int value = values[middle];

        if (value > target) {
            return divideAndConquer(values, target, start, middle - 1);
        }
        if (value < target) {
            return divideAndConquer(values, target, middle + 1, end);
        }
        return middle;
    }
}