/****************************************************
 * A program to compute and print Fibonacci numbers *
 * using recursion and iteration.                   *
 ****************************************************/

#include <stdio.h>

/* Function prototypes */
void recfib(int,int,int,int);
void iterfib(int);


int main()
{
  int fnum = -1;

  /* Read in a value until a valid one is provided */
  do
  {
    printf("Please enter the number of Fibonacci");
    printf(" numbers you would like to see: ");
    scanf("%d", &fnum);
  } while(fnum < 1);

  printf("Printing %d Fibonacci numbers recursively\n", fnum);

  /* Print the Fibonacci numbers using recursion. */
  recfib(fnum,0,1,0);

  printf("Printing %d Fibonacci numbers iteratively\n", fnum);

  /* Print the Fibonacci numbers iteratively. */
  iterfib(fnum);

  return 0;

}

/* function recfib                                       *
 * This function prints Fibonacci numbers recursivly.    *
 * parameters:                                           *
 *   n - the number of Fibonacci numbers left to print   *
 *   f_1 - the current Fibonacci number                  *
 *   f_2 - the next Fibonacci number                     *
 *   k - the current position in the list of Fibonacci   *
 *       numbers                                         */

void recfib(int n, int f_1, int f_2, int k)
{
  /* If we are on the last Fibonacci number, print it and return */
  if(n == 0)
  {
    printf("%5d: %5d\n",k,f_1);
  }
  /* Otherwise print the current Fibonacci number and call recfib
   * again to print the next number
   */
  else
  {
    printf("%5d: %5d\n",k,f_1);
    recfib(n-1, f_2, f_2+f_1, k+1);
  }
}

/* function iterfib                                   * 
 * This function prints Fibonacci numbers iteratively *
 * parameters:                                        *
 *   fnum - the number of Fibonacci numbers to print  */

void iterfib(int fnum)
{
  /* Declare variables */
  int i = 0, current = 1, current_1 = 0, temp;

  /* Begin the loop to print out the Fibonacci numbers */
  for(i = 0; i <= fnum; i++)
  {
    /* If printing out f_0 or f_1, just print them */
    if(i == 0)
      printf("%5d: %5d\n", i, 0);
    else if(i == 1)
      printf("%5d: %5d\n", i, 1);
    /* otherwise, compute the current Fibonacci number using
     * the previous two Fibonacci numbers
     */
    else
    {
      temp = current;
      current = current + current_1;
      current_1 = temp;
      printf("%5d: %5d\n", i, current);
    }
  }
}