#include<iostream>
#include<iostream>
#include<stdio.h>
using namespace std;
long fac (int n);
int main () {
int n, i;
cout<<"请输入正整数:";
cin>>n ;
cout<<fac(n)<<endl;
cout<<"按enter继续"<<endl;
fflush(stdin);
getchar();
main();
return 0;
}
long fac (int n)
{
if(n==1)
return 1;
else
return (2*n-1)*fac(n-1);
}
运行结果: