递归和非递归分别实现求第n个斐波那契数

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int fib(int n) {
if (n == 1 || n == 2) {
return 1;
}
else
{
return fib(n - 1) + fib(n - 2);
}
}
int main()
{
int n;
scanf("%d", &n);
fib(n);
printf("%d", fib(n));
printf("\n");
system(“pause”);
return 0;
}

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int fib(int n)
{
if (n == 1 || n == 2)
{
return 1;
}
int i;
int a = 1;
int b= 1;
int c = 0;
for (i = 3; i <= n; i++)
{
c=a + b;
a=b;
b=c;
}
return c;
}
int main()
{
int n;
scanf("%d", &n);
fib(n);
printf("%d", fib(n));
printf("\n");
system(“pause”);
return 0;
}