9.斐波那契数列

#include <iostream>
#include <ctime>
#include <time.h>
using namespace std;



long long Fibonacci_Recursion(unsigned int n)
{
    if(n <= 1)
        return n;

    return Fibonacci_Recursion(n-1) + Fibonacci_Recursion(n-2);
}


long long Fibonacci(unsigned int n)
{
    if(n<=1)
        return n;

    long long f1 = 0;
    long long f2 = 1;
    long long fn = 0;
    for(unsigned int i=2; i<=n; i++)
    {
        fn = f1 + f2;

        f1 = f2;
        f2 = fn;
    }

    return fn;
}

int main()
{

    clock_t tick = clock();
    cout<<Fibonacci_Recursion(50)<<endl;
    cout<<clock()-tick<<endl;

    tick = clock();
    cout<<Fibonacci(50)<<endl;
    cout<<clock()-tick<<endl;
    return 0;
}