用C语言做,1~20的阶乘的和

Question

要求过程,越快越好

Answer 1

#include "stdio.h"
void main()
{
doulbe sum=0,f=1;
for(int i=1;i<=20;i++)
{
f*=i;
sum+=f;
}
printf("1!+2!+...+20!=%0.0lf",sum);
}

Answer 2

#include <stdio.h>

double FacSum(double x, double y)
{
return y > 1 ? FacSum((x+1)*(y-1), y-1) : x;
}

int main()
{
printf("%lf", FacSum(20, 20));
}

Answer 3

int i,p,sigma;

p = 1; //阶乘单项变量
sigma = 0; //求和结果

for(i=0;i<20;i++;)
{
p = p*(i+1);
sigma = sigma + p;
}