Multiply Two Matrix Using Multi-dimensional Arrays using C++

This program asks user to enter two matrices and this program multiplies these two matrix and displays it. If you don't know matrix multiplication, visit this page to learn, how two matrix can be multiplied.

Source code to multiply two matrix in C++ programming

#include <iostream>
using namespace std;
int main()
{
    int a[10][10], b[10][10], mult[10][10], r1, c1, r2, c2, i, j, k;
    cout << "Enter rows and columns for first matrix: ";
    cin >> r1 >> c1;
    cout << "Enter rows and columns for second matrix: ";
    cin >> r2 >> c2;

/* If colum of first matrix in not equal to row of second matrix, asking user to enter the size of matrix again. */
    while (c1!=r2)
    {
        cout << "Error! column of first matrix not equal to row of second.";
        cout << "Enter rows and columns for first matrix: ";
        cin >> r1 >> c1;
        cout << "Enter rows and columns for second matrix: ";
        cin >> r2 >> c2;
    }

/* Storing elements of first matrix. */
    cout << endl << "Enter elements of matrix 1:" << endl;
    for(i=0; i<r1; ++i)
    for(j=0; j<c1; ++j)
    {
        cout << "Enter element a" << i+1 << j+1 << " : ";
        cin >> a[i][j];
    }

/* Storing elements of second matrix. */
    cout << endl << "Enter elements of matrix 2:" << endl;
    for(i=0; i<r2; ++i)
    for(j=0; j<c2; ++j)
    {
        cout << "Enter element b" << i+1 << j+1 << " : ";
        cin >> b[i][j];
    }

/* Initializing elements of matrix mult to 0.*/
    for(i=0; i<r1; ++i)
    for(j=0; j<c2; ++j)
    {
       mult[i][j]=0;
    }

/* Multiplying matrix a and b and storing in array mult. */
    for(i=0; i<r1; ++i)
    for(j=0; j<c2; ++j)
    for(k=0; k<c1; ++k)
    {
        mult[i][j]+=a[i][k]*b[k][j];
    }

/* Displaying the multiplication of two matrix. */
    cout << endl << "Output Matrix: " << endl;
    for(i=0; i<r1; ++i)
    for(j=0; j<c2; ++j)
    {
        cout << " " << mult[i][j];
        if(j==c2-1)
            cout << endl;
    }
    return 0;
}

Output

Enter rows and column for first matrix: 3
2
Enter rows and column for second matrix: 3
2
Error! column of first matrix not equal to row of second.

Enter rows and column for first matrix: 2
3
Enter rows and column for second matrix: 3
2

Enter elements of matrix 1:
Enter elements a11: 3
Enter elements a12: -2
Enter elements a13: 5
Enter elements a21: 3
Enter elements a22: 0
Enter elements a23: 4

Enter elements of matrix 2:
Enter elements b11: 2
Enter elements b12: 3
Enter elements b21: -9
Enter elements b22: 0
Enter elements b31: 0
Enter elements b32: 4

Output Matrix:
24 29
6  25

In this program, user is asked to enter the size of two matrix at first. The column of first matrix should be equal to row of second matrix for multiplication. If this condition is not satisfied then, the size of matrix is again asked using while loop. Then, user is asked to enter two matrix and finally the output of two matrix is calculated and displayed.