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

const int SUCCESS = 0;
const int FAILURE = 1;

int factorial_iterative(int x, int* result)
{
  if (x < 0)
   return FAILURE; 

  if (x == 0)
  {
    *result = 1;
    return SUCCESS;
  }

  *result = 1;

  while (x > 0)
  {
    *result *= x--;
  }

  return SUCCESS;
}

int factorial_recursive(int x, int* result)
{
  if (x < 0)
   return FAILURE; 

  if (x == 0 || x == 1)
  {
    *result = 1;
    return SUCCESS;
  }

  int tmp = x;

  int rc = factorial_recursive(x-1, &tmp);

  if ( SUCCESS != rc )
    return FAILURE;

  *result = x * tmp;

  return SUCCESS;
}

int main(int argc, char** argv)
{
  int result, rc;

  if ( argc != 2)
  {
    printf("usage: %s input_num\n", argv[0]);
    return FAILURE;
  }

  rc = factorial_iterative(atoi(argv[1]), &result);
  if (SUCCESS == rc)
    printf("iterative %d\n", result);
  else
    printf("iterative failure\n");

  rc = factorial_recursive(atoi(argv[1]), &result);
  if (SUCCESS == rc)
    printf("recursive %d\n", result);
  else
    printf("recursive failure\n");

  return SUCCESS;
}