Question

求（1！+2！+3！+4！+...+20！）的C语言编程

Answer 1

#include<stdio.h>
#define N 20
void main()
{
int f(int n);
long sum=0;
int i;
for(i=1;i<=N;i++)
sum+=f(i);
printf("sum=%ld\n",sum);
}
int f(int n)
{
if(n==1)
return 1;
else if(n>1)
return n*f(n-1);
return 0;
}

Answer 2

#include "stdio.h"
#include "conio.h"
main()
{
float n,s=0,t=1;
for(n=1;n<=20;n++)
{
t*=n;
s+=t;
}
printf("1+2!+3!...+20!=%e\n",s);
getch();
}

Answer 3

float fuc(float n)
{
return (0==n)?1:(n*fuc(n-1));
}

int _tmain(int argc, _TCHAR* argv[])
{
float i;
float sum=0;
for(i=20;i>0;i--)
{
//printf("%f\n",fuc(i));
sum+=fuc(i);
}
printf("%f",sum);
getchar();
return 0;
}