求某个数的阶乘

此代码易学 

#include<iostream>
using namespace std;
int fac(int);
int main()
{
	int n;
	while (cin >> n)
	{
		cout << n << "!= " << fac(n) << endl;
	}

	return 0;
}

int fac(int x)
{
	register int i, f = 1; 
	for (i = 1; i <= x; i++)
		f *= i;

	return f;
}

下面这个较为高效。 

#include <iostream>
using namespace std;
int main()
{
	int i, n, factorial=1;
	cout << "请输入数字：";
	cin >> n;
	for (i = 1; i <= n; i++)
	{
		factorial *= i;
	}
	cout << factorial << endl;
	return 0;
}