用C语言编辑求和1/1!-3/2!+5/3!-7/4!+9/5!

用C语言编辑求和1/1!-3/2!+5/3!-7/4!+9/5!

int main()
{
int a,b,k=1,i,j;
double s=0;

for(i=0;i<5;i++)
{
a = 1 + i * 2;
for(j=i+1,b=1;j>0;j--)
{
b *= j;
}
s += (double)a/b*k;
k *= -1;
}

printf("s=%f\n",s);
getchar();
}

#include "stdio.h"

float fun(int n) {  if(n==1)   return 1;  else  return n*fun(n-1); }

void main() {  float sum=1/fun(1)-3/fun(2)+5/fun(3)-7/fun(4)+9/fun(5);    printf("%f\n",sum); }

int jiecheng(int n) { if(n==1||n==0)return 1; else return n*jiecheng(n-1); } double fun(int n) { if(n==1)return 1; else if(!(n%2)) return fun(n-1)-1.0*(2*n-1)/jiecheng(n); else return 1.0*(2*n-1)/jiecheng(n)-fun(n-1); } void main() { printf("%lf",fun(5)); }