计算斐波那契数字 递归和非递归

#include<stdio.h>
#include<stdlib.h>
int main()
{
	int n = 0;
	int ret = 0;
	scanf("%d",&n);
	ret = fib(n);
	printf("%d\n", ret);
	system("pause");
	return 0;
}
int main()
{
	int i = 0;
	int n = 0;
	int sum = 0;
	int j = 1;
	int p = 0;
	scanf("%d", &n);
	for (i = 1; i <=n; i++)
	{
		p = 1;
		for (j = 1; j <=i; j++)
		{
			p = p*j;
		}
		sum = sum + p;
	}
	printf("sum = %d\n", sum);
	system("pause");
	return 0;
}

#include<stdio.h>
#include<stdlib.h>
int fib(int n)
{
	int a = 1;
	int b = 1;
	int c = 1;
	while (n > 2)
	{
		c = a + b;
		a = b;
		b = c;
		n--;
	}
	return c;
}
int main()
{
	int ret = 0;
	int n = 0;
	scanf("%d", &n);
	ret = fib(n);
	printf("%d", ret);
	system("pause");
}