第二周任务二：自定义求阶乘

#include<iostream>

using namespace std;

long fac(int n)//求 N的阶乘
{
int j = 1;

while ( n > 0 )
{

j = j * n;

n--;

}
return j;
}

int main()
{
int m,n,C_mn;

cout << "请输入m,n的值" << endl;

cin >> m >> n;

C_mn = fac(m)/( fac(n)*( fac(m-n) ) );

cout << "所求组合数为" << C_mn << endl;

return 0;
}