求一個整數的階乘 C/C++

//法一：

#include "stdio.h"
void main()
{
	int n,p=1;
	printf("Please enter an integer N:n");
	scanf("%d",&n);
	for(;n>0;n--)
		p*=n;
	printf("n!=%d",p);
}


//法二：遞歸法

#include "stdio.h"
int rec(int n)
{
	if(n==0)return 1;
	return n*rec(n-1);
}


void main()
{
	int i;
	printf("Please enter an integer N:n");
	scanf("%d",&i);
	printf("n!=%d",rec(i));
}