[数据结构与算法]c语言实现斐波那契数列递归 和 非递归算法

斐波那契数列规律是从第三个数开始每个数是前两个数的和
递归:

#include ＜stdio.h＞
int Fibon(int n)
{
if (n < 0)
{
printf("n is error!\n");
return -1;
}
else if(n＜2)
   return n == 0? 0:1;
else if（n＞=2)
return Fibon(n-1) + Fibon(n-2);
}

int main()
{
int n;
print("输入查询的第几个数")
scanf("%s",n);
print("斐波那契数列第%d项为:%d",n,Fibon(n))
}

非递归

#include ＜stdio.h＞
int Fibon(int n)
{
    if (n < 0)
    {
        printf("n is error!\n");
        return -1;
    }
    int n1 = 1;
    int n2 = 2;
    int n3 = 3;
    for (int i = 3;i <= n;++i)
    {
        n3 = n1+n2;
        n1 = n2;
        n2 = n3;
    }
    return n3;
}
 
int main()
{
    int n;
    print("Please input Fibon index:")
    scanf("%s",n);
    print("斐波那契数列第%d项为:%d",n,Fibon(n))
}