c语言求1！+2！+3！+……+20!

#include<stdio.h>
void main()
{
long t,sum;
int i;
t=1;sum=0;i=1;
while(i<=20)
{
t=t*i;
sum=sum+t;
i=i+1;
}
printf("sum=%ld\n",sum);
}

用二重循环结构，不用函数：

int main()
{
int i, j, jc, sum = 0;

for (i = 1; i<=20; i++)
{
jc=1;
for(j = 1; j <= i; j++)
{
jc*=j;
}
sum += jc;
}
printf("sum:%d\n", sum);
return 0;
}

int main()
{
int i, sum = 0;
for (i = 1; i<=20; i++)
{
sum += jc(i);
}
printf("sum:%d\n", sum);
return 0;
}

int jc(int n)
{
int i, f = 1;

for (i = 1; i <= n; i++)
{
f *= i;
}
return f;
}