組合數求解公式

#include < iostream >


using namespace std;


long fac ( int n )    //求n的階乘
{
long p;
if( n == 0 || n == 1 )
p = 1;
else
p = n * fac ( n - 1 );
return p;
}


int main()
{
int n , m , p ;
cout << " 請輸入兩個數：" << endl;


cin >> n;
cin >> m;
p = fac ( m ) / ( fac ( n ) * fac ( m - n ) );


cout << p << endl;


return 0;

}