Question

Please create a C program with the following C code declares variable mtx of matrix type, and dynamically allocates memory for mtx. It will then get keyboard input for the N-by-N matrix. Subsequently, the program de-allocates (free) the memory of the matrix.

A. Your task is to write the codes to dynamically allocate and de-allocate the memory for the matrix.

B. Subsequently, you have to modify the above code so that now the program will first ask the user to enter the size of the matrix, accept two matrices of the same size (maximum size 5-by-5) where each element of these matrices are manually input, and then perform matrix addition. The program will then output all the input matrices and the matrix addition results, both to the standard output screen and also to the text file called matrix.txt.

Answer 1

Below is the source code for the above:

We basically allocate a memory block of size N*N and access the memory locations using pointers

Code(gcc 5.1.0):

#include<stdio.h>
#include <stdlib.h>

//function for freeing memory
int freemem(int *var,int N){
   int i,j;
   for (i = 0; i < N; i++)
   {
       int* Ptr = var[i*N];
       free(Ptr);
   }
}

int main(){

int i, j, N, *intMatrix1,*intMatrix2,*intMatrix3;
//Taking size of the array as input  
printf("Enter N:\t");
scanf("%d", &N);

intMatrix1 = (int *)malloc(N * N * sizeof(int));
intMatrix2 = (int *)malloc(N * N * sizeof(int));
intMatrix3 = (int *)malloc(N * N * sizeof(int));
//Taking input for Matrix 1:
printf("Enter Matrix 1:\t");
for (i = 0; i < N; ++i)
{
      for (j = 0; j < N; ++j)
      {
        scanf("%d", &intMatrix1[i*N + j]);
      }
}
//Taking input for Matrix 2:
printf("Enter Matrix 2:\t");
for (i = 0; i < N; ++i)
{
      for (j = 0; j < N; ++j)
      {
        scanf("%d", &intMatrix2[i*N + j]);
      }
}
//Matrix additon taking place
for (i = 0; i < N; ++i)
{
      for (j = 0; j < N; ++j)
      {
        intMatrix3[i*N + j] = intMatrix1[i*N + j] + intMatrix2[i*N + j];
      }
}
printf("Resultant Matrix :\t");
//Printing the matrix
for (i = 0; i < N; i++) {
   for (j = 0; j < N; j++) {
          printf("%d ", intMatrix3[i*N + j]);
       }
}

//Freeing the declared memory
freemem(intMatrix1,N);
freemem(intMatrix2,N);
freemem(intMatrix3,N);
    
       
}

Output:

Enter N:        2
Enter Matrix 1: 1
1
1
1
Enter Matrix 2: 2
2
2
2
Resultant Matrix :      3 3 3 3
--------------------------------
Process exited after 14.64 seconds with return value 3221226356
Press any key to continue . . .