how to declare 2 d array using malloc

#include <stdio.h> 
#include <stdlib.h> 
  
int main() 
{ 
    int r = 3, c = 4; 
    int *arr = (int *)malloc(r * c * sizeof(int)); 
  
    int i, j, count = 0; 
    for (i = 0; i <  r; i++) 
      for (j = 0; j < c; j++) 
         *(arr + i*c + j) = ++count; 
  
    for (i = 0; i <  r; i++) 
      for (j = 0; j < c; j++) 
         printf("%d ", *(arr + i*c + j)); 
  
   /* Code for further processing and free the  
      dynamically allocated memory */
    
   return 0; 
}