// fib.c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <assert.h>

int
fib(int n)
{
  if(n <= 0) {
    return 0;
  } else if(n == 1) {
    return 1;
  } else {
    return fib(n-1) + fib(n-2);
  }
}

int FibHash[100];

// uses memoization
int
memoFib(int n)
{
  int ret;

  // what happens if you leave out this line?
  if (n < 1) return 0;

  if(FibHash[n]) {
    return FibHash[n];
  } else {
    ret = memoFib(n-1) + memoFib(n-2);
    FibHash[n] = ret;
    return ret;
  }
}

// uses dynamic programming
int
fib2(int n)
{
  int *a;
  int i;
  int ret;
  
  if(n < 2) {
    return 1;
  } else {
    a = malloc(sizeof(*a) * (n+1));
    assert(a);
    
    a[0] = a[1] = a[2] = 1;
    
    for(i = 3; i <= n; i++) {
      a[i] = a[i-1] + a[i-2];
    }
  }
  
  ret = a[n];
  free(a);
  return ret;
}


int main(int argc, char ** argv){

  if (argc == 1) {
    fprintf(stderr, "Usage: fib [integers]+\n");
    exit(1);
  }

  FibHash[0] = 0;
  FibHash[1] = 1;
  for (int k = 2; k < 100; k++) FibHash[k] = 0;

  clock_t t;
  double time_taken;
  for (int i = 1; i < argc; i++){
    int j = atoi(argv[i]);
    if (j > 0) {

      t = clock();
      printf("fib(%d) = %d  \t", j, fib(j));
      t = clock() - t;
      time_taken = ((double) t)/CLOCKS_PER_SEC;
      printf("Time: %f\n", time_taken);

      t = clock();
      printf("memoFib(%d) = %d  \t", j, memoFib(j));
      t = clock() - t;
      time_taken = ((double) t)/CLOCKS_PER_SEC;
      printf("Time: %f\n", time_taken);

      t = clock();
      printf("fib2(%d) = %d  \t", j, fib2(j));
      t = clock() - t;
      time_taken = ((double) t)/CLOCKS_PER_SEC;
      printf("Time: %f\n", time_taken);
    }
  }

  return (0);

}