Program to multiply two matrices

Program to multiply two matrices

Given two matrices, the task to to multiply them. Matrices can either be square or rectangular.

Multiplication of Square Matrices:

// C program to multiply two square matrices.

#include <stdio.h>

 // This function multiplies mat1[][] and mat2[][],

// and stores the result in res[][]

void multiply(int mat1[][N], int mat2[][N], int res[][N])

{

    int i, j, k;

    for (i = 0; i < N; i++)

    {

        for (j = 0; j < N; j++)

        {

            res[i][j] = 0;

            for (k = 0; k < N; k++)

                res[i][j] += mat1[i][k]*mat2[k][j];

        }

    }

}

 int main()

{

    int mat1[N][N] = { {1, 1, 1, 1},

                    {2, 2, 2, 2},

                    {3, 3, 3, 3},

                    {4, 4, 4, 4}};

 int mat2[N][N] = { {1, 1, 1, 1},

                    {2, 2, 2, 2},

      {3, 3, 3, 3},

                    {4, 4, 4, 4}};

 int res[N][N];  // To store result

    int i, j;

    multiply(mat1, mat2, res);

   printf("Result matrix is \n");

    for (i = 0; i < N; i++)

    {

        for (j = 0; j < N; j++)

           printf("%d ", res[i][j]);

        printf("\n");

    }

 return 0;

}

Output:

Result matrix is

10 10 10 10

20 20 20 20

30 30 30 30

40 40 40 40

Multiplication of Rectangular Matrices :

// C program to multiply two rectangular matrices

#include<stdio.h>

// Multiplies two matrices mat1[][] and mat2[][]

// and prints result.

// (m1) x (m2) and (n1) x (n2) are dimensions

// of given matrices.

void multiply(int m1, int m2, int mat1[][m2],

              int n1, int n2, int mat2[][n2])

{

    int x, i, j;

    int res[m1][n2];

    for (i = 0; i < m1; i++) {

        for (j = 0; j < n2; j++) {

            res[i][j] = 0;

            for (x = 0; x < m2; x++) {

                *(*(res + i) + j) += *(*(mat1 + i) + x) *

                                     *(*(mat2 + x) + j);

            }

        }

    }

    for (i = 0; i < m1; i++) {

        for (j = 0; j < n2; j++) {

            printf("%d ", *(*(res + i) + j));

            printf("\n");

    }

}

 // Driver code

int main()

{

    int mat1[][2] = { { 2, 4 }, { 3, 4 } };

    int mat2[][2] = { { 1, 2 }, { 1, 3 } };

    int m1 = 2, m2 = 2, n1 = 2, n2 = 2;

    multiply(m1, m2, mat1, n1, n2, mat2);

    return 0;

}

Output:

6 16

7 18