Main.java

import java.util.Scanner;

public class Main{
    int [][] matrix;

    Main(int [][] mat)
    {
        matrix=mat;
    }


    public static Main add(Main a,Main b)
    {
        if (a.matrix.length==0) return null;
        int[][] c = new int[a.matrix.length][a.matrix[0].length];
        for(int i=0;i<a.matrix.length;i++){
            for(int j=0;j<a.matrix[0].length;j++){
                c[i][j]=a.matrix[i][j]+b.matrix[i][j];    //use - for subtraction
            }
        }
        return new Main(c);
    }
    public static int[][] matrixMultiplication(
            int[][] matrix1, int rows1, int cols1,
            int[][] matrix2, int rows2, int cols2)
            throws Exception
    {

        // Required condition for matrix multiplication
        if (cols1 != rows2) {
            throw new Exception("Invalid matrix given.");
        }

        // create a result matrix
        int resultMatrix[][] = new int[rows1][cols2];

        // Core logic for 2 matrices multiplication
        for (int i = 0; i < resultMatrix.length; i++)
        {
            for (int j = 0;
                 j < resultMatrix[i].length;
                 j++)
            {
                for (int k = 0; k < cols1; k++)
                {
                    resultMatrix[i][j]
                            += matrix1[i][k] * matrix2[k][j];
                }
            }
        }
        return resultMatrix;
    }
    public static Main multiply(Main a,Main b)
    {
        if (a.matrix.length == 0||b.matrix.length==0) return null;
        try {
            return new Main(matrixMultiplication(a.matrix,a.matrix.length,a.matrix[0].length,b.matrix,b.matrix.length,b.matrix[0].length));
        } catch (Exception e) {
            return null;
        }
    }
    public static Main transpose(Main m)
    {
        if (m.matrix.length==0) return null;
        int[][] B = new int[m.matrix[0].length][m.matrix.length];
        int i, j;
        for (i = 0; i < m.matrix[0].length; i++)
            for (j = 0; j < m.matrix.length; j++)
                B[i][j] = m.matrix[j][i];

        return new Main(B);
    }
    public static Main rotate(Main m)
    {
        int [][] matrix = m.matrix;
        int n = matrix.length;
        if (n == 1) {
            return null;
        }
        for (int k=0;k<3;k++){
            for (int i = 0; i < n / 2; i++) {
                for (int j = i; j < n - 1 - i; j++) {
                    int temp = matrix[i][j];
                    matrix[i][j] = matrix[n - 1 - j][i];
                    matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];
                    matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];
                    matrix[j][n - 1 - i] = temp;
                }
            }
        }
        return new Main(matrix);
    }
    public void print()
    {
        for(int i=0;i<matrix.length;i++)
        {
            for(int j=0;j<matrix[0].length;j++)
            {
                System.out.print(matrix[i][j]+" ");
            }
            System.out.println();
        }
    }

    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        int option=s.nextInt();
        if(option==1)
        {
            int r1=s.nextInt();
            int c1=s.nextInt();
            int [][] m1=new int[r1][c1];
            for(int i=0;i<r1;i++)
            {
                for(int j=0;j<c1;j++)
                {
                    m1[i][j]=s.nextInt();
                }
            }
            Main mat1=new Main(m1);
            int r2=s.nextInt();
            int c2=s.nextInt();
            int [][] m2=new int[r2][c2];
            for(int i=0;i<r2;i++)
            {
                for(int j=0;j<c2;j++)
                {
                    m2[i][j]=s.nextInt();
                }
            }
            Main mat2=new Main(m2);
            Main ans=Main.add(mat1,mat2);
            ans.print();
        }
        else if (option==2)
        {
            int r1=s.nextInt();
            int c1=s.nextInt();
            int [][] m1=new int[r1][c1];
            for(int i=0;i<r1;i++)
            {
                for(int j=0;j<c1;j++)
                {
                    m1[i][j]=s.nextInt();
                }
            }
            Main mat1=new Main(m1);
            int r2=s.nextInt();
            int c2=s.nextInt();
            int [][] m2=new int[r2][c2];
            for(int i=0;i<r2;i++)
            {
                for(int j=0;j<c2;j++)
                {
                    m2[i][j]=s.nextInt();
                }
            }
            Main mat2=new Main(m2);
            Main ans=Main.multiply(mat1,mat2);
            ans.print();
        }
        else if(option==3)
        {
            int r1=s.nextInt();
            int c1=s.nextInt();
            int [][] m1=new int[r1][c1];
            for(int i=0;i<r1;i++)
            {
                for(int j=0;j<c1;j++)
                {
                    m1[i][j]=s.nextInt();
                }
            }
            Main mat1=new Main(m1);
            Main ans=Main.transpose(mat1);
            ans.print();
        }
        else
        {
            int r1=s.nextInt();
            int c1=s.nextInt();
            int [][] m1=new int[r1][c1];
            for(int i=0;i<r1;i++)
            {
                for(int j=0;j<c1;j++)
                {
                    m1[i][j]=s.nextInt();
                }
            }
            Main mat1=new Main(m1);
            Main ans=Main.rotate (mat1);
            ans.print();
        }
    }
}