求1+2!+3!+...+20!的和，使用函数实现

// factorial.cpp : 定义控制台应用程序的入口点。

/*

Main.cpp

Written By Namer_Mega ,Thanks for sharing your knowledge

*/

#include <iostream>

using namespace std;

int factorial(int x)

{
int product = 1,k;
int sum = 0;
for(k = 1; k <= x ;k++)
{
product = product * k;
sum += product;
}
return sum;

}

int main()

{
cout<<factorial(20)<<endl;
return 0;

}