Fibonacci数列 3

题目描述 Description
斐波纳契数列是这样的数列：
f1 = 1
f2 = 1
f3 = 2
f4 = 3
....
fn = fn-1 + fn-2
 
输入一个整数n

求fn

输入描述 Input Description

一个整数n, n<= 40

输出描述 Output Description

一个整数fn

样例输入 Sample Input

3

样例输出 Sample Output

2

数据范围及提示 Data Size & Hint

n<=40

代码：

数组版：

#include 
using namespace std;
int fibonacci[45];
int main()
{
    int n;
    cin >> n;
    fibonacci[0] = 0;
    fibonacci[1] = 1;
    fibonacci[2] = 1;
    for (int i = 3; i <= n; i++)
        fibonacci[i] = fibonacci[i-1] + fibonacci[i-2];
    cout << fibonacci[n];
    return 0;
}

递归版：

#include 
using namespace std;
int fibonacci(int n)
{
    int fn;
    if (n == 1 || n == 2)
        fn = 1;
    else
        fn = fibonacci(n - 1) + fibonacci(n - 2);
    return fn;
}
int main()
{
    int n;
    cin >> n;
    int result = fibonacci(n);
    cout << result;
    return 0;
}