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

void readMatrix(int **, int, int);
void printMatrix(int **, int, int);
int **allocMatrix(int, int);
void freeMatrix(int **a, int m);
int ** sumMatrix(int **a, int **b, int m, int n);
int ** mulMatrix(int **a, int **b, int m, int n, int p);

int main(){
  int **a,  **b,  **c;
  int m, n, p;
  printf("enter the number m of rows of first matrix:");
  scanf("%d", &m);
  printf("enter the number n of columns of first matrix/rows of second matrix:");
  scanf("%d", &n);
  printf("enter the number p of columns of second matrix:");
  scanf("%d", &p);
  a = allocMatrix(m, n);
  b = allocMatrix(n, p);
  if( a == NULL || b == NULL)
  {
    printf("not enough memory\n");
    return 1;
  }
  printf("enter the first matrix:\n");
  readMatrix(a,m,n);
  printf("enter the second matrix:\n");
  readMatrix(b,n,p);
  c = mulMatrix(a,b,m,n,p);
  if( c == NULL){
    printf("not enough memory\n");
    return 1;
  }
  printf("The product of the matrices:\n");
  printMatrix(a,m,n);
  printf("and\n");
  printMatrix(b,n,p);
  printf("are\n");
  printMatrix(c,m,p);

}

int ** sumMatrix(int **a, int ** b, int m, int n)
{
  int **c;
  c = allocMatrix(m,n);
  if( c == NULL) return NULL;
  for(int i = 0; i < m; i ++){
    for(int j = 0; j < n; j ++){
      c[i][j] = a[i][j] + b[i][j];
    }
  }
  return c;
}
    
  
void readMatrix(int **a, int m, int n){
  for(int i = 0; i < m; i ++){
    for(int j = 0; j < n; j ++){
      printf("\tenter [%d][%d] th entry:",i,j);
      scanf("%d",&a[i][j]);
    }
  }
}
void printMatrix(int **a, int m, int n){
  for(int i = 0; i < m; i ++){
    printf("\t");
    for(int j = 0; j < n; j++){
      printf("%d\t",a[i][j]);
    }
    printf("\n");
  }
}
      
int **allocMatrix(int m, int n)
{
  int **a;
  a = (int **) malloc(m * sizeof(int *));
  if( a == NULL) return NULL;
  for(int i = 0 ; i < m; i ++){
    a[i] = (int *) malloc(n * sizeof(int));
    if(a[i] == NULL){
      for(int j = 0; j < i; j ++){
	free(a[j]);
	a[j]=NULL;
      }
      return NULL;
    }
  }
  return a;
}

int **mulMatrix(int **a, int **b, int m, int n, int p)
{
  int **c;
  c = allocMatrix(m,p);
  if ( c == NULL ) return NULL;
  for(int i = 0; i < m; i ++){
    for(int k=0; k < p; k++){
      c[i][k] = 0;
      for(int j = 0; j < n; j ++){
        c[i][k] = c[i][k]  + a[i][j] * b[j][k];
      }
    }
  }
  return c;
}