Java Program to Accept a Matrix of Order M x N & Interchange the Diagonals

Problem Description: Write a Java program that accepts a matrix of M × N order and then interchange diagonals of the matrix.

Steps: 

1. We can only interchange diagonals for a square matrix.

2. Create a square matrix of size [M × M].

3. Check the matrix is a square matrix or not. If the matrix is square then follow step 3 else terminate the program.

4. Apply logic for interchange diagonal of the matrix some logic is given below.

Method 1: Swap element a[i][i] and a[i][n – i -1]

               for (j = 0; j < m; j++) {

               temp = a[j][j];

               a[j][j] = a[j][n – 1 – j];

               a[j][n – 1 – j] = temp;

           }

Example:

Java

//  Java Program to Accept a Matrix of Order M x N &
//  Interchange the Diagonals

import java.util.Scanner;
public class InterchangeDiagonals {
    public static void main(String[] args)
    {
        // declare variable
        int m, n, i, j, temp;

        // create a object of scanner class
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter number of rows ");

        // take number of rows
        m = sc.nextInt();

        System.out.print("Enter number of columns ");

        // take number of columns
        n = sc.nextInt();

        // declare a mxn order array
        int a[][] = new int[m][n];

        // if block it's execute when m is equals to n
        if (m == n) {
            System.out.println(
                "Enter all the values of matrix ");

            // take the matrix inputs
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    a[i][j] = sc.nextInt();
                }
            }

            System.out.println("original Matrix:");

            // print the original matrix
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    System.out.print(a[i][j] + " ");
                }
                System.out.println("");
            }

            // perform interchange
            for (j = 0; j < m; j++) {
                temp = a[j][j];
                a[j][j] = a[j][n - 1 - j];
                a[j][n - 1 - j] = temp;
            }
            System.out.println(
                " after interchanging diagonals of matrix ");

            // print interchanged matrix
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    System.out.print(a[i][j] + " ");
                }
                System.out.println("");
            }
        }

        // else block it's only execute when m is not equals
        // to n
        else {
            System.out.println("Rows not equal to columns");
        }
    }
}

Output:

Enter number of rows 3

Enter number of columns 3

Enter all the values of matrix  

1

2

3

4

5

6

7

8

9

Original Matrix:

1   2   3  

4   5   6  

7   8   9  

After interchanging diagonals of matrix  

3   2   1  

4   5   6  

9   8   7 

Example 2:

Java

//  Java Program to Accept a Matrix of Order MxN &
//  Interchange the Diagonals

import java.util.Scanner;
public class InterchangeDiagonals {
    public static void main(String[] args)
    {
        // declare variable
        int m, n, i, j, temp;

        // create a object of scanner class
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter number of rows ");

        // take number of rows
        m = sc.nextInt();

        System.out.print("Enter number of columns ");

        // take number of columns
        n = sc.nextInt();

        // declare a mxn order array
        int a[][] = new int[m][n];

        // if block it's execute when m is equals to n
        if (m == n) {
            System.out.println(
                "Enter all the values of matrix ");

            // take input matrix
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    a[i][j] = sc.nextInt();
                }
            }

            System.out.println("original Matrix:");

            // print original matrix
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    System.out.print(a[i][j] + " ");
                }
                System.out.println("");
            }

            // performing interchange
            for (j = 0; j < m; j++) {
                temp = a[j][j];
                a[j][j] = a[j][n - 1 - j];
                a[j][n - 1 - j] = temp;
            }
            System.out.println(
                " after interchanging diagonals of matrix ");

            // print interchanged matrix
            for (i = 0; i < m; i++) {
                for (j = 0; j < n; j++) {
                    System.out.print(a[i][j] + " ");
                }
                System.out.println("");
            }
        }

        // else block it's only execute when m is not equals
        // to n
        else {
            System.out.println("Rows not equal to columns");
        }
    }
}

Output:

Enter number of rows 2

Enter number of columns 1

Enter all the values of matrix  

1

2

Rows not equal to columns