/*
 * Demonstrate that recursion can be slow
 *
 * gcc -o fibonacci fibonacci.c my_timing.c
 */

#include <stdio.h>
#include "my_timing.h"
 
/* recursive method: double recursion, variable n grows exponentially */ 
unsigned long FibonacciR (unsigned n) {
	if (n > 2) 
		return FibonacciR(n-1) + FibonacciR(n-2);
	else
		return 1;
}

/* without recursion */
unsigned long Fibonacci (unsigned n) {
	if (n <= 1) {
		return n;
	}
	
	unsigned long curr = 1;
	unsigned long prev = 1;
	for (int i = 2; i < n; ++i) {
		unsigned long temp = curr;
		curr += prev;
		prev = temp; 
	}
	
	return curr;
}

long SumR( long n ) {
    if (n == 0 || (n > 100000 && n % 100 == 0)) {
        printf( "n=%ld @%p\n", n, &n );
    }
    if (n < 1) {
        return 0;
    }
    else {
        return SumR( n-1 ) + n;
    }
}

long Sum( long n ) {
    long ret = 0;
    for (int i = 1; i < n; i++) {
        ret += i;
    }
    return ret;
}

int main () {
	double t1, t2, t3;
	unsigned d;
	printf( "Enter desired Fibonacci number: ");
	while (scanf("%d", &d) != 0) {
		printf("Entered: %d\n", d);
		t1 = get_time_sec();
		unsigned i = FibonacciR(d);
// 		unsigned i = SumR(d);
//         unsigned i = 0;
		t2 = get_time_sec();
		unsigned j = Fibonacci(d);
// 		unsigned j = Sum(d);
		t3 = get_time_sec();
		printf("FibonacciR number is: %u, Time: %f sec\n", i, t2 - t1);
		printf("Fibonacci number is: %u, Time: %f sec\n", j, t3 - t2);
    	printf( "Enter desired Fibonacci number: ");
	}
	
	return 0;
}