Description

* To multiply two matrices, the number of columns of the first matrix should be equal 
   to the number of rows of the second matrix.
* If multiplication is not possible, then it should print error message.

C/C++

/* C program to multiply two matrices */
//Save it as MultiplyTwoMatrix.c

#include<stdio.h>
int main(){

    int i, j, k, row1, column1, row2, column2, sum=0;

    printf("Enter the number of rows of first matrix : ");
    scanf("%d",&row1);

    printf("Enter the number of columns of first matrix : ");
    scanf("%d",&column1);
    
    //Declaring first matrix
    int matrix1[row1][column1];
    
    //Reading input for first matrix
    printf("Enter the elements of first matrix : \n");
    for(i=0;i<row1;i++) {
        for(j=0;j<column1;j++) {
            printf("matrix1[%d][%d] : ",i,j);
            scanf("%d",&matrix1[i][j]);
        }
    }
    
    //Displaying Output for first matrix
    printf("The elements of first matrix : \n");
    for(i=0;i<row1;i++) {
        for(j=0;j<column1;j++) {
            printf("%d ",matrix1[i][j]);
        }
        printf("\n");
    }

    printf("Enter the number of rows of second matrix : ");
    scanf("%d",&row2);

    printf("Enter the number of columns of second matrix : ");
    scanf("%d",&column2);

    //Declaring second matrix
    int matrix2[row2][column2];

    //Reading input for second matrix
    printf("Enter the elements of second matrix : \n");
    for(i=0;i<row2;i++) {
        for(j=0;j<column2;j++) {
            printf("matrix2[%d][%d] : ",i,j);
            scanf("%d",&matrix2[i][j]);
        }
    }

    //Displaying Output for second matrix
    printf("The elements of second matrix : \n");
    for(i=0;i<row2;i++) {
        for(j=0;j<column2;j++) {
            printf("%d ",matrix2[i][j]);
        }
        printf("\n");
    }

    //Declaring Result matrix after multiplication
    int matrix3[row1][column2];

    if(column1!=row2){
        printf("Matrix cannot be multiplied");
    }
    else{
        for (i = 0; i < row1; i++) {
            for (j = 0; j < column2; j++) {
                for (k = 0; k < column1; k++) {
                    sum = sum + matrix1[i][k]*matrix2[k][j];
                }
                matrix3[i][j] = sum;
                sum = 0;
            }
        }
        //Displaying Output after multiplication
        printf("The matrix after multiplication is : \n");
        for(i=0;i<row1;i++) {
            for(j=0;j<column2;j++) {
                printf("%d ",matrix3[i][j]);
            }
            printf("\n");
        }
    }
    return 0;
}

Input:
Enter the number of rows of first matrix : 2
Enter the number of columns of first matrix : 3
Enter the elements of first matrix :
matrix1[0][0] : 1
matrix1[0][1] : 2
matrix1[0][2] : 3
matrix1[1][0] : 4
matrix1[1][1] : 5
matrix1[1][2] : 6
Enter the number of rows of second matrix : 3
Enter the number of columns of second matrix : 2
Enter the elements of second matrix :
matrix2[0][0] : 1
matrix2[0][1] : 4
matrix2[1][0] : 2
matrix2[1][1] : 5
matrix2[2][0] : 3
matrix2[2][1] : 6

Output:
The elements of first matrix :
1 2 3
4 5 6
The elements of second matrix :
1 4
2 5
3 6
The matrix after multiplication is :
14 32
32 77

Java

/* Java program to multiply two matrices */
//Save it as MultiplyTwoMatrix.java

import java.io.*;
import java.util.Scanner;
public class MultiplyTwoMatrix {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        
        int i, j, k, row1, column1, row2, column2, sum=0;

        System.out.println("Enter the number of rows of first matrix : ");
        row1 = scanner.nextInt();

        System.out.println("Enter the number of columns of first matrix : ");
        column1 = scanner.nextInt();
        
        //Declaring first matrix
        int matrix1[][] = new int[row1][column1];

        //Reading input for first matrix
        for (i = 0; i < row1; i++) {
            for (j = 0; j < column1; j++) {
                System.out.println("matrix1[" + i + "]" + "[" + j + "] : ");
                matrix1[i][j] = scanner.nextInt();
            }
        }
        
        //Displaying Output for first matrix
        System.out.println("The first matrix is : ");
        for (i = 0; i < row1; i++) {
            for (j = 0; j < column1; j++) {
                System.out.print(matrix1[i][j] + " ");
            }
            System.out.println();
        }

        System.out.println("Enter the number of rows of second matrix : ");
        row2 = scanner.nextInt();

        System.out.println("Enter the number of columns of second matrix : ");
        column2 = scanner.nextInt();

        //Declaring second matrix
        int matrix2[][] = new int[row2][column2];

        //Reading input for second matrix
        System.out.println("Enter the elements of second matrix : ");
        for (i = 0; i < row2; i++) {
            for (j = 0; j < column2; j++) {
                System.out.println("matrix2[" + i + "]" + "[" + j + "] : ");
                matrix2[i][j] = scanner.nextInt();
            }
        }
        
        //Displaying Output for second matrix
        System.out.println("The second matrix is : ");
        for (i = 0; i < row2; i++) {
            for (j = 0; j < column2; j++) {
                System.out.print(matrix2[i][j] + " ");
            }
            System.out.println();
        }

        //Declaring Result matrix after multiplication
        int matrix3[][] = new int[row1][column1];

        if(column1!=row2){
            System.out.println("Matrix cannot be multiplied");
        }
        else{
            for (i = 0; i < row1; i++) {
                for (j = 0; j < column2; j++) {
                    for (k = 0; k < column1; k++) {
                        sum = sum + matrix1[i][k]*matrix2[k][j];
                    }
                    matrix3[i][j] = sum;
                    sum = 0;
                }
            }
            //Displaying Output after multiplication
            System.out.println("The matrix after multiplication is : ");
            for (i = 0; i < row1; i++) {
                for (j = 0; j < column2; j++) {
                    System.out.print(matrix3[i][j] + " ");
                }
                System.out.println();
            }
        }
    }
}

Input:
Enter the number of rows of first matrix : 
2
Enter the number of columns of first matrix : 
3
matrix1[0][0] : 
1
matrix1[0][1] : 
2
matrix1[0][2] : 
3
matrix1[1][0] : 
4
matrix1[1][1] : 
5
matrix1[1][2] : 
6 
Enter the number of rows of second matrix : 
3
Enter the number of columns of second matrix : 
2
Enter the elements of second matrix : 
matrix2[0][0] : 
1
matrix2[0][1] : 
4
matrix2[1][0] : 
2
matrix2[1][1] : 
5
matrix2[2][0] : 
3
matrix2[2][1] : 
6

Output:
The first matrix is : 
1 2 3 
4 5 6
The second matrix is : 
1 4 
2 5 
3 6 
The matrix after multiplication is : 
14 32 
32 77

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