[John]

Originally Posted by HAL 9000

I made a non recursive Fibonacci function in C for fun because it can't solve 100 fast with recursion.
Did anyone else besides me do it this way

#include<stdio.h>

/*prototypes*/
double fib(int n);

int main(void)
{
	int i;
	
	for(i = 0;i <= 100;++ i)
	{
		printf("%1.0f \n",fib(i));
	}

	return 0;
}

/*non recursive fibonacci function*/
double fib(int n)
{
	double prev = -1;
	double result = 1;
	double sum;
	int i;
	
	for(i = 0;i <= n;++ i)
	{
		sum = result + prev;
		prev = result;
		result = sum;
	}
	
	return result;
}

A few months ago, I posted this:

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <math.h>
using namespace std;
 
//Non-recrusive: O(1)
unsigned long fib(int n)
{
     return (1/sqrt(5)) * (pow(((1 + sqrt(5)) / 2), n) - pow(((1 - sqrt(5)) / 2), n));
}
 
//Recrusive: O(n)
unsigned long fib2(int n)
{
    if(n <= 2) return 1;
    else return fib2(n - 1) + fib2(n - 2);
}
 
//Iterative: O(n)
unsigned long fib3(int n)
{
    int u = 0;
    int v = 1;
    int i, t;
 
    for(i = 2; i <= n; i++)
    {
        t = u + v;
        u = v;
        v = t;
    }
    return v;        
}