C 斐波那契數列

1.題目

遞歸和非遞歸分別實現求第n個斐波那契數。

2.程序代碼

#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>
#include <windows.h>

int fib_num2(int num)//用遞歸實現求第n個斐波那契數列
{
    if (num <= 2)
    {
        return 1;
    }
    return fib_num2(num - 1) + fib_num2(num - 2);
}

int fib_num1(int num)//用非遞歸實現求第n個斐波那契數列
{
    int i = 0;
    int arr[50] = {1, 1};//定義一個長度爲50的數組來存放斐波那契數列，
                    //並給前兩位初始化爲1

    for (i = 0; i < num; i++)
    {
        if (i >= 2)
        {
            arr[i] = arr[i - 1] + arr[i - 2];
        }
    }
    return arr[num - 1];
}

int main()
{
    int n = 0;
    int ret = 0;//存放自定義函數的返回值

    printf("please input a number about Fibonacci numbers:");
    scanf("%d", &n);

    printf("%d\n", ret = fib_num1(n));
    printf("%d\n", ret = fib_num2(n));

    system("pause");
    return 0;
}

3.執行結果