Question

Develop a C program for matrix multiplication focusing on using malloc and pointers WITHOUT USING BRACKETS [] !!

* DO not use [ ] 'brackets', focus on using malloc, calloc, etc...

Program will ask user for the name of the text file to be read
Read the datafile with format:
1
2
1
1 2
3
4
So the first three lines will represent m, n, p (Matrix A: m x n ||| Matrix B: n x p), follwing are the two matrices.
Representing:
A = |1 2|     B = |3|
                         |4|

------------------------------------------------
example input and output:
Matrix A contents:
    1    2
    3    4
    5    6

Matrix B contents:
    7    8    9   10
   11   12   13   14

Matrix A * B is:
   29   32   35   38
   65   72   79   86
101 112 123 134

The datafile read for this example is:
3
2
4
1 2
3 4
5 6
7 8 9 10
11 12 13 14

Answer 1

If you have any doubts, please give me comment...

#include<stdio.h>

#include<stdlib.h>

int main(){

    char filename[50];

    int m, n, p, i, j, k;

    int **A, **B, **mult;

    printf("Enter filename: ");

    scanf("%s", filename);

    FILE *fp;

    fp = fopen(filename, "r");

    if(fp==NULL){

        printf("Unable to open file\n");

        return 0;

    }

    fscanf(fp, "%d %d %d", &m, &n, &p);

    A = (int **)malloc(m*sizeof(int *));

    for(i=0; i<m; i++){

        *(A+i) = (int *)malloc(n*sizeof(int));

        for(j=0; j<n; j++){

            fscanf(fp, "%d", (*(A+i)+j));

        }

    }

    B = (int **)malloc(n*sizeof(int *));

    for(i=0; i<n; i++){

        *(B+i) = (int *)malloc(p*sizeof(int));

        for(j=0; j<p; j++)

            fscanf(fp, "%d", (*(B+i)+j));

    }

    

    mult = (int **)malloc(m*sizeof(int *));

    for(i=0; i<m; i++)

        *(mult+i) = (int *)malloc(p*sizeof(int));

    

    printf("Matrix A contents:\n");

    for(i=0; i<m; i++){

        for(j=0; j<n; j++){

            printf("%4d", *(*(A+i)+j));

        }

        printf("\n");

    }

    printf("Matrix B contents:\n");

    for(i=0; i<n; i++){

        for(j=0; j<p; j++){

            printf("%4d", *(*(B+i)+j));

        }

        printf("\n");

    }

    for(i=0; i<m; i++){

        for(j=0; j<p; j++){

            *(*(mult+i)+j) = 0;

            for(int k=0; k<n; k++){

                *(*(mult+i)+j) += *(*(A+i)+k) * *(*(B+k)+j);

            }

        }

    }

    printf("Matrix A * B is:\n");

    for(i=0; i<m; i++){

        for(j=0; j<p; j++){

            printf("%4d", *(*(mult+i)+j));

        }

        printf("\n");

    }

    for(i=0; i<m; i++){

        free(*(A+i));

        free(*(mult+i));

    }

    for(i=0; i<n; i++)

        free(*(B+i));

    

    free(A);

    free(B);

    free(mult);

    return 0;

}