计算Fibonacci数的几种算法对比

#include "MyTimer.h"
#include <iostream>
#include <cmath>

using namespace std;

unsigned int fib_1(unsigned int n)
{
    if(n<=1) return n;
    return fib_1(n-1)+fib_1(n-2);
}

unsigned int fib_2(unsigned int n)
{
    unsigned int f[100];
    int i;
    memset(f,0,sizeof(unsigned int));
    f[1]=f[2]=1;
    for(i=3;i<100;i++)
        f[i]=f[i-1]+f[i-2];
    return f[n];
}

unsigned int fib_3(unsigned int n)
{
    if(n<=1) return n;
    unsigned int prev=0,next=1,fib;
    for(unsigned int i=2;i<=n;i++)
    {
        fib=prev+next;
        prev=next;
        next=fib;
    }
    return fib;
}

unsigned int fib_4(unsigned int n)
{
    double x,y;
    unsigned int fib;
    x=(1+sqrt(5))/2;
    y=(1-sqrt(5))/2;
    fib=(pow(x,n)-pow(y,n))/sqrt(5);
    return fib;
}

unsigned int deMoivreFib (unsigned int n)
{//等同于fib_4
    double x;
    x=(1+sqrt(5))/2;
    return ceil(exp(n*log(x)-log(sqrt(5))) - .5);
}

int main() {
    int n;
    MyTimer mt;
    while(cin>>n)
    {
 /*     mt.Start();
        cout<<fib_1(n)<<"     ";
        mt.Stop();
        cout<<"fib_1: "<<mt.costTime<<" us"<<endl;
 */
        mt.Start();
        cout<<fib_2(n)<<"     ";
        mt.Stop();
        cout<<"fib_2: "<<mt.costTime<<" us"<<endl;

        mt.Start();
        cout<<fib_3 (n)<<"     ";
        mt.Stop();
        cout<<"fib_3: "<<mt.costTime<<" us"<<endl;
        
        mt.Start();
        cout<<fib_4 (n)<<"     ";
        mt.Stop();
        cout<<"fib_4: "<<mt.costTime<<" us"<<endl;    
        
        mt.Start();
        cout<<deMoivreFib (n)<<"     ";
        mt.Stop();
        cout<<"deMoF: "<<mt.costTime<<" us"<<endl;
    }
    return 0;
}