Matrix-Search-D&C

import java.util.*;

public class Main {
    public static void main(String[] args) {
        // Example usage
        int[][] X = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };

        int k = 5;
        int top_left_i = 0;
        int top_left_j = 0;
        int bottom_right_i = X.length - 1;
        int bottom_right_j = X[0].length - 1;

        Pair<Integer, Integer> result = find(X, k, top_left_i, top_left_j, bottom_right_i, bottom_right_j);

        if (result.getKey() == -1 && result.getValue() == -1) {
            System.out.println("Element not found.");
        } else {
            System.out.println("Element found at position (" + result.getKey() + ", " + result.getValue() + ").");
        }
    }

    public static Pair<Integer, Integer> find(int[][] X, int k, int top_left_i, int top_left_j, int bottom_right_i, int bottom_right_j) {
        int m_i = (top_left_i + bottom_right_i) / 2;
        int m_j = (top_left_j + bottom_right_j) / 2;

        if (X[m_i][m_j] == k) {
            return new Pair<>(m_i, m_j);
        }

        if (top_left_i == bottom_right_i && top_left_j == bottom_right_j) {
            return new Pair<>(-1, -1);  // not found
        }

        if (top_left_i > bottom_right_i || top_left_j > bottom_right_j) {
            return new Pair<>(-1, -1);  // not found
        }

        if (X[m_i][m_j] > k) {
            Pair<Integer, Integer> pos = find(X, k, top_left_i, top_left_j, m_i - 1, m_j - 1);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }

            pos = find(X, k, m_i, top_left_j, bottom_right_i, m_j - 1);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }

            pos = find(X, k, top_left_i, m_j, m_i - 1, bottom_right_j);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }
        } else {
            Pair<Integer, Integer> pos = find(X, k, m_i + 1, m_j + 1, bottom_right_i, bottom_right_j);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }

            pos = find(X, k, m_i + 1, top_left_j, bottom_right_i, m_j);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }

            pos = find(X, k, top_left_i, m_j + 1, m_i, bottom_right_j);
            if (!pos.equals(new Pair<>(-1, -1))) {
                return pos;
            }
        }

        return new Pair<>(-1, -1);  // not found
    }
}