program C++ kombinasi & permutasi

 hanya coba2 saj,, masih kurang optimal ki,,??? wkwwkkwkwkwkw


#include <iostream.h>
#include <cstdlib>
#include <stdio.h>
#include <conio.h>
long int fak (long int x);
int main()




{
int n,r, Prts,pilihan,p;
char ulang;
do
{


cout<<"PERHITUNGAN KOMBINASI DAN PERMUTASI"<<endl;
cout<<"1. KOMBINASI"<<endl;
cout<<"2. PERMUTASI"<<endl;
cout<<"3. EXIT"<<endl;
cout<<endl<<endl;
cout<<"Pilihan Anda : ";cin>>pilihan;
switch (pilihan)
{
case 1 :
cout<<" Program Menghitung Kombinasi(nCr)";
cout<<endl;
cout<<" Masukkan Nilai n : "; cin>>n;
cout<<endl;
cout<<" Masukkan Nilai r : "; cin>>r;
cout<<endl;
if (n>r){
Prts = fak(n)/(fak(n-r)*fak (r));
cout<<endl;
printf(" Kombinasinya adalah: %d",Prts);
cout<<endl; }
else if (n<r){
cout<<"data tak valid";}
cout<<endl ;
break;
case 2 :
cout<<" Program Menghitung Permutasi(nPr)";
cout<<endl;
cout<<" Masukkan Nilai n : "; cin>>n;
cout<<endl;
cout<<" Masukkan Nilai r : "; cin>>r;
cout<<endl;
if (n>r){
Prts = fak (n)/fak(n-r);
cout<<endl;

printf(" Permutasinya adalah: %d",Prts);
cout<<endl; }
else if (n<r){
cout<<"data tak valid";}
cout<<endl ;
break;
case 3 :
cout<<"Exitâ?¦"<<endl;
break;
default:
cout<<"Menu tidak tersedia"<<endl;
break;
}
cout<<"Kembali ke Menu Utama (y/n)?";cin>>ulang;
}while(ulang == 'y');
}


long int fak (long int n)
{
int f;
if (n<=1)
{
f=1;
}
else
{
f=n*fak(n-1);
}
return (f);
}

saran n koment apabila salah dan kurang2 nya,,, terima kasihhh