Java Program to Rotate the Matrix 90 degree

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In the previous article, we have discussed Java Program to Clockwise Rotate the Matrix Elements

In this article we are going to see how we can write a program to rotate the matrix 90 degree in JAVA language.

Java Program to Rotate the Matrix 90 degree

A 3*3 Matrix is having 3 rows and 3 columns where this 3*3 represents the dimension of the matrix. Means there are 3*3 i.e. total 9 elements in a 3*3 Matrix.

Let’s understand it in more simpler way.

                   | A00   A01   A02 |
Matrix A =  | A10   A11   A12 |
                   | A20   A21   A22 | 3*3
  • Matrix A represents a 3*3 matrix.
  • ‘A‘ represents the matrix element
  • ‘Aij‘ represents the matrix element at it’s matrix position/index.
  • ‘i‘ represents the row index
  • ‘j‘ represents the column index
  • Means A00=Aij  where i=0 and j=0,  A01=aij where i=0 and j=1 and like this.
  • Here we have started row value from 0 and column value from 0.

Let’s see different ways to to rotate the Matrix 90 degree.

Method-1: Java Program to Rotate the Matrix 90 degree By Static Initialization of Array Elements

Approach:

  • Initialize and an array of size 3×3, with elements.
  • Transpose the matrix and then reverse the elements
  • Print the matrix.

Program:

public class matrix{
    public static void main(String args[])
    {
        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = {{19,25,32},{40,54,62},{70,20,60}};
        int row, col ;

        System.out.print("\nThe matrix elements are : ");
        printMatrix(arr);
        // Calls the transpose function inside the rotate array function
        rotateArr(trans(arr));
    }

     // Method to find the transpose
    static int[][] trans(int[][] mat)
    {
        int row, col, trans[][] = new int[3][3];
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                trans[row][col] = mat[col][row];
        return trans;
    }
    
    // Reverses the array
    static void rotateArr(int arr[][])
    {
        for(int i=0;i<3;i++)
            for(int j=0,k=2;j<k;j++,k--)
            {
                int temp = arr[j][i];
                arr[j][i] = arr[k][i];
                arr[k][i] = temp;
            }
            System.out.print("\nThe rotated matrix is : ");
            printMatrix(arr);
    }

    // Method to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
        System.out.print("\n");
    }

}


Output:

The matrix elements are : 
19 25 32 
40 54 62 
70 20 60

The rotated matrix is : 
32 62 60 
25 54 20 
19 40 70

Method-2: Java Program to Rotate the Matrix 90 degree By Dynamic Initialization of Array Elements

Approach:

  • Declare one array of size 3×3.
  • Ask the user for input of array elements and store them in the array using two for loops.
  • Transpose the matrix and then reverse the elements.
  • Print the matrix.

Program:

import java.util.*;

public class matrix
{
    public static void main(String args[])
    {
        //Scanner class to take input
        Scanner scan = new Scanner(System.in);

        // Initializing the 3X3 matrix i.e. 2D array
        int arr[][] = new int[3][3];
        int row, col ;

        // Taking matrix1 input
        System.out.print("Enter matrix elements : ");
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                arr[row][col] = scan.nextInt();

        System.out.print("\nThe matrix elements are:");
        printMatrix(arr);
        // Calls the transpose function inside the rotate array function
        rotateArr(trans(arr));
    }

     // Method to find the transpose
    static int[][] trans(int[][] mat)
    {
        int row, col, trans[][] = new int[3][3];
        for(row=0;row<3;row++)
            for(col=0;col<3;col++)
                trans[row][col] = mat[col][row];
        return trans;
    }
    
    // Reverses the array
    static void rotateArr(int arr[][])
    {
        for(int i=0;i<3;i++)
            for(int j=0,k=2;j<k;j++,k--)
            {
                int temp = arr[j][i];
                arr[j][i] = arr[k][i];
                arr[k][i] = temp;
            }
            System.out.print("\nThe rotated matrix is");
            printMatrix(arr);
    }

    // Method to print the matrix
    static void printMatrix(int arr[][])
    {
        int row, col;
        // Loop to print the elements
        for(row=0;row<3;row++)
        {
            // Used for formatting
            System.out.print("\n");
            for(col=0;col<3;col++)
            {
                System.out.print(arr[row][col]+" ");
            }
        }
    }

}


Output:

Enter matrix elements : 9 8 3 4 5 6 7 3 8
The matrix elements are:
9 8 3 
4 5 6 
7 3 8 
The rotated matrix is
3 6 8 
8 5 3 
9 4 7

Guys who are serious about learning the concepts of the java programming language should practice this list of programs in java and get a good grip on it for better results in exams or interviews.

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