/* computation of elements of the Fibonnaci sequence with and without dynamic prog.
 */

#include <stdio.h>
#include <time.h>     // for time

int fibSeq1(int n) {
  if (n <= 1 )
    return 1;
  else
    return fibSeq1 (n-1) + fibSeq1 (n-2);
}

int fibSeq2Helper (int n, int fibArr [ ]) {
  if (fibArr[n] != 0)
    return fibArr[n];
  if (n <= 1)
    return fibArr[n] = 1;
  else
    return fibArr[n] = fibSeq2Helper (n-1, fibArr)
                       + fibSeq2Helper (n-2, fibArr);
}

int fibSeq2 (int n) {
  //create NS INIRIliw local array for bookkeeping
  int arr [n+1];
  for (int i = 0; i <= n; i++)
    arr[i] = 0;
  return fibSeq2Helper (n, arr);
}

int main ( ) {
  int reps = 100;  // number of times call repeated to help timings
  
  printf ("timing of two functions to compute the nth Fib number\n");
  printf ("    (each function call repeated %d times)\n", reps);
  printf ("               Approach 1          Approach 2\n");
  printf ("     n      Fib[n]     time    Fib[n]     time\n");

  int n;
  int value;
  clock_t start_time, end_time;
  double elapsed_time;

  for (n = 1; n <= 45; n += 4) {
    printf ("%6d", n);

    // tim first approach
    start_time = clock ();
    for (int j = 0; j < reps; j++)
      value = fibSeq1 (n);
    end_time = clock();
    elapsed_time = (end_time - start_time) / (double) CLOCKS_PER_SEC;
    printf ("%11d   %6.1lf", value, elapsed_time);

    // time second approach
    start_time = clock ();
    for (int k = 0; k < reps; k++)
      value = fibSeq2 (n);
    end_time = clock();
    elapsed_time = (end_time - start_time) / (double) CLOCKS_PER_SEC;
    printf ("%11d   %6.1lf\n", value, elapsed_time);
  }
}