Java Program to Interchange the Diagonals

In this article, we will understand how to interchange the diagonals. The matrix has a row and column arrangement of its elements. A matrix with m rows and n columns can be called as m × n matrix.

Individual entries in the matrix are called element and can be represented by a[i][j] which suggests that the element a is present in the ith row and jth column.

Below is a demonstration of the same −

Suppose our input is −

The matrix is defined as:
4 5 6
1 2 3
7 8 9

The desired output would be −

The matrix after interchanging the elements:
6 5 4
1 2 3
9 8 7

Algorithm

Step 1 - START
Step 2 - Declare an integer matrix namely input_matrix, and two integer value namely matrix_size and temp.
Step 3 - Define the values.
Step 4 - Iterate over each element of the matrix using multiple for-loops and swap the required elements of the matrix using a temporary variable.
Step 5 - Display the result
Step 5 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

public class InterchangeDiagonals {
   public static int matrix_size = 3;
   public static void main (String[] args) {
      int input_matrix[][] = {
         {4, 5, 6},
         {1, 2, 3},
         {7, 8, 9}
      };
      System.out.println("The matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix[i][j] + " ");
         }
         System.out.println();
      }
      for (int i = 0; i < matrix_size; ++i)
         if (i != matrix_size / 2) {
            int temp = input_matrix[i][i];
            input_matrix[i][i] = input_matrix[i][matrix_size - i - 1];
            input_matrix[i][matrix_size - i - 1] = temp;
         }
         System.out.println("\nThe matrix after interchanging the elements: ");
         for (int i = 0; i < matrix_size; ++i) {
            for (int j = 0; j < matrix_size; ++j)
               System.out.print(input_matrix[i][j]+" ");
            System.out.println();
         }
      }
}

Output

The matrix is defined as:
4 5 6
1 2 3
7 8 9

The matrix after interchanging the elements:
6 5 4
1 2 3
9 8 7

Example 2

Here, we encapsulate the operations into functions exhibiting object-oriented programming.

public class InterchangeDiagonals {
   public static int matrix_size = 3;
   static void interchange_diagonals(int input_matrix[][]) {
      for (int i = 0; i < matrix_size; ++i)
      if (i != matrix_size / 2) {
         int temp = input_matrix[i][i];
         input_matrix[i][i] = input_matrix[i][matrix_size - i - 1];
         input_matrix[i][matrix_size - i - 1] = temp;
      }
      System.out.println("\nThe matrix after interchanging the elements: ");
      for (int i = 0; i < matrix_size; ++i) {
         for (int j = 0; j < matrix_size; ++j)
         System.out.print(input_matrix[i][j]+" ");
         System.out.println();
      }
   }
   public static void main (String[] args) {
      int input_matrix[][] = {
         {4, 5, 6},
         {1, 2, 3},
         {7, 8, 9}
      };
      System.out.println("The matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix[i][j] + " ");
         }
         System.out.println();
      }
      interchange_diagonals(input_matrix);
   }
}

Output

The matrix is defined as:
4 5 6
1 2 3
7 8 9

The matrix after interchanging the elements:
6 5 4
1 2 3
9 8 7