PERMUTASI & KOMBINASI

#include <cstdlib>
#include <iostream>

using namespace std;
class matdis{

      friend istream& operator>>(istream&, matdis&);
      friend ostream& operator<<(ostream&, matdis&);
      public:
             matdis();
             int permutasi();
             int kombinasi();
             void pilihan();
             void exit();
      private:
              int n,r,x,y,z,a,p,c;
              };
      matdis::matdis(){
                       cout<<"\t==PROGRAM PERMUTASI DAN KOMBINASI=="<<endl;
                       cout<<"\t+++++++++++DENGAN PROSEDUR"<<endl;
                       cout<<"\t====SILAHKAN PILIH PILIHAN ANDA===="<<endl;
                       cout<<"\t+++++++++++1. PERMUTASI +++++++++++"<<endl;
                       cout<<"\t+++++++++++ 2. COMBINASI +++++++++++"<<endl;
                       cout<<"\t+++++++++++ 0. EXIT      +++++++++=++"<<endl;
                       cout<<"\t+++++++++++ TERIMA KASIH ++++++++++++"<<endl;
                       };
                     
      int matdis::permutasi(){
           cout<<"Program Menghitung Permutasi"<<endl;
           cout<<"Masukkan n harus lebih besar dari r :"<<endl;
           cout<<"Masukkan n :"; cin>>n;
           cout<<"Masukkan r :"; cin>>r;
           x=1;
           y=1;
           for(int i=1; i<=n; i++){
                   x=x*i;
                   }
           for(int j=1; j<=(n-r); j++){
                   y=y*j;
                   }
           p=x/y;
           cout<<"Nilai n ="<<n<<endl;
           cout<<"Nilai r ="<<r<<endl;
           cout<<"Nilai n! ="<<x<<endl;
           cout<<"Hasil (n-r)! ="<<y<<endl;
           cout<<"Hasil Permutasi "<<"("<<n<<","<<r<<") : "<<p<<endl;
           pilihan();
           return p;
           }
         
      int matdis::kombinasi(){
           cout<<"Program Menghitung Kombinasi"<<endl;
           cout<<"Masukkan n harus lebih besar dari r :"<<endl;
           cout<<"Masukkan n :"; cin>>n;
           cout<<"Masukkan r :"; cin>>r;
           x=1;
           y=1;
           z=1;
           a=(n-r);
           for(int i=1; i<=n; i++){
                   x=x*i;
                   }
           for(int j=1; j<=r; j++){
                   y=y*j;
                   }
           for(int k=1; k<=a; k++){
                   z=z*k;
                   }
           c=x/(z*y);
           cout<<"Nilai n ="<<n<<endl;
           cout<<"Nilai r ="<<r<<endl;
           cout<<"Nilai n! ="<<x<<endl;
           cout<<"Hasil r! ="<<y<<endl;
           cout<<"Nilai (n-r)! ="<<z<<endl;
           cout<<"Hasil Kombinasi "<<"("<<n<<","<<r<<") : "<<c<<endl;
           pilihan();
           return c;
           }
      void matdis::pilihan(){
                int pil;
                cout<<endl;
                cout<<"masukan pilihan anda = ";
                cin>>pil;
                switch(pil){
                 case 1 : permutasi ();break;
                 case 2 : kombinasi ();break;
                 case 0 : exit (); break;
                 default :
                         cout<<"Maaf anda salah tulis"<<endl;
                         cout<<"Pilih kembali Pilihan "<<endl;
                         pilihan();
                          break;     
                 }}
      void matdis::exit(){
                          cout << "TERIMA KASIH"<<endl;
                          }

int main(int argc, char *argv[])
{
    matdis x;
    x.pilihan();
    system("PAUSE");
    return EXIT_SUCCESS;
}