Code 5 - Factorial

#include <iostream>
#include <limits>
#include <cmath>
using namespace std;

int pilihan, angka;

void askPilihan(), askNumber(int max);
int getNearestBelowNumber(int number);
int getNumbersBetweenNumbers(int min, int max);

class Count {
    public:
        virtual void startCount() {
            cout<<"Virtual for startCount"<<endl;
        }
};

class Factorial : public Count{
    private:
        int hasil;

    public:
        void startCount() {

            hasil = 1;
            for(int i=angka; i>0; --i){
                hasil *= i;
            }

            cout<<"The Result of Factorial "<<angka<<" :"<<endl;
            cout<<hasil<<endl;
        }
};

class Fibonacci : public Count{

    private:
        int t1, t2, nextTerm;

    public:
        void startCount() {

            t2 = 1;
            t1 = 0;
            nextTerm = 0;
            cout<<"The Result of Fibonacci "<<angka<<" :"<<endl;
            for (int i = 1; i <= angka; ++i){

                // Prints the first two terms.
                if(i == 1)
                {
                    cout << t1 << " ";
                    continue;
                }
                if(i == 2)
                {
                    cout << t2 << " ";
                    continue;
                }
                nextTerm = t1 + t2;
                t1 = t2;
                t2 = nextTerm;

                cout << nextTerm << " ";
            }
        }
};

class Binary : public Count{

    private:
        int hasil;

    public:
        void startCount() {

            hasil=0;
            cout<<"The Result of Binary Number "<<angka<<" :"<<endl;
            cout<<"0 ";
            while (angka>0){
                if(hasil>0){
                    for(int i=0; i<getNumbersBetweenNumbers(getNearestBelowNumber(angka), hasil); i++){
                        cout<<"0 ";
                    }
                }
                hasil = getNearestBelowNumber(angka);
                cout<<"1 ";
                angka -= pow(2,hasil);
            }
            for(int i=0; i<getNumbersBetweenNumbers(getNearestBelowNumber(angka), hasil); i++){
                cout<<"0 ";
            }
        }
};

int getNumbersBetweenNumbers(int min, int max){
    return max-(min+1);
}

int getNearestBelowNumber(int number){

    int hasil = 1, i=0;
    while(hasil<number){
        hasil *= 2;
        ++i;
    }
    if(hasil>number) return i-1;
    else return i;
}

void welcome(){
    cout<<"Factorial, Fibonacci, and Binary Calculation"<<endl;
    cout<<"============================================\n"<<endl;

    cout<<"1. Factorial"<<endl;
    cout<<"2. Fibonacci"<<endl;
    cout<<"3. Binary Number"<<endl;
    cout<<"4. Exit"<<endl;

    askPilihan();
}

void askNumber(int max){
    cout<<"Input the number[1-"<<max<<"]: ";
    cin>>angka;
    if(!cin || angka<1 || angka>max){
        cin.clear();
        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        askNumber(max);
    }
}

void hitung(Count *count) { count->startCount(); }

void askPilihan(){

    cout<<"Choose: ";
    cin>>pilihan;
    if(!cin){
        cin.clear();
        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        askPilihan();
    }

    Factorial *faktorial = new Factorial;
    Fibonacci *fibonaci = new Fibonacci;
    Binary *binari = new Binary;
    switch(pilihan){
        case 1:
            askNumber(20);
            hitung(faktorial);
            break;

        case 2:
            askNumber(20);
            hitung(fibonaci);
            break;

        case 3:
            askNumber(100);
            hitung(binari);
            break;

        case 4:
            exit(0);
            break;

        default:
            cout<<"Pilihan yang dimasukkan salah"<<endl;
            cin.clear();
            cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
            askPilihan();
    }
}

main(){
    welcome();
}