19-2h tutoring https://git.io/Je4r2

w1-1.cpp

// https://rextester.com/KAY13591

// import modules
#include <iostream>

// define Character class
class Character {
private:
  // declare fields
  int x;
  int hp;

public:
  // constructor
  Character(int initX, int initHp): x(initX), hp(initHp) {
    // print message
    std::cout << "캐릭터 생성" << std::endl;
  }

  // print character's status
  void print() {
    std::cout << "상태 출력 => x: "
      << x
      << ", HP: "
      << hp << std::endl;
  }

  // 'x' setter
  void setX(int newX) {
      std::cout << "캐릭터 이동" << std::endl;
    x = newX; // set new x
  }
};

// entry point function
int main(void) {
    Character c { 0, 100 };
    
    c.print();
    
    c.setX(90);
    
    c.print();
  
    return 0;
}

w1-2.cpp

// https://rextester.com/RPWF16481

// import modules
#include <iostream>
#include <vector>

// using namespace for 'string' type
using namespace std;

// define Todo Class
class Todo {
    private:
    vector<string> todos; // todo array

    public:
    // Constructor
    Todo() {
      // creation message
      std::cout << "Created todo class" << std::endl;
    }

    // add todo into the 'todos' list
    int add(string todo) {
      todos.push_back(todo); // push_back

      return todos.size(); // return this size
    }

    // print todos
    void print() {
      for (string &t : todos) { // for-eaching
        std::cout << t << std::endl; // print todo
      }
    }
};

// entry point function
int main(void) {
    // create Todo instance
    Todo todo;

    // append todos
    todo.add("item 1");
    todo.add("item 2");
    todo.add("item 3");

    // print
    todo.print();
  
    return 0;
}

w2-1.cpp

// https://rextester.com/HLH22324

// import module
#include <iostream>

// define Apple class
class Apple {
    public:
    // print method
    void print() {
        // print message
        std::cout << "Apple" << std::endl;
    }
};

// define People class
class People {
    private:
    Apple * apple; // apple field variable (using pointer type)

    public:
    // constructor
    // pointer type var => to point to a Heap instance (Apple instance)
    People(Apple * a) { // shallow copy
        apple = a;
    }

    // eat function
    void eat() {
        // call print method
        apple->print(); // or `(*apple).print();`
    }
};

// entry point
int main()
{
    // create instances
    Apple * a = new Apple();
    People * p = new People(a);

    // call eat
    p->eat(); // or `(*p).eat();`

    return 0;
}

w3-1.cpp

// https://rextester.com/BROY71588

#include <iostream>

using namespace std;

class Ticket {
    private:
    static int cnt;
    
    public:
    Ticket() {
        cnt++; // Ticket::cnt++;
    }

    static int count() {
        return cnt; // Ticket::cnt;
    }
};

int Ticket::cnt = 0;

int main()
{    
    Ticket t1;
    Ticket t2;
    Ticket t3;
    
    cout << Ticket::count() << endl;
}

w4-1.cpp

// https://rextester.com/LECWL51773
//g++  5.4.0

#include <iostream>

class B; // declaration class

class A {
    private:
    int numberA;
    
    public:
    A(): numberA(100) { }
    
    friend int add(A, B);
};

class B{
    private:
    int numberB;
    
    public:
    B(): numberB(200) { }
    
    friend int add(A, B);
};

int add(A a, B b) {
    return a.numberA + b.numberB;
}

int main()
{
    A a;
    B b;
    
    std::cout << add(a, b);
    
    return 0;
}

w4-2.cpp

// https://rextester.com/ISUB26014
//g++  5.4.0

#include <iostream>

class Counter {
    private:
    int value;
    
    public:
    Counter(): value(0) { }
    
    int operator ++ () {
        value += 2;
        std::cout << value << std::endl;
        return value;
    }
};

int main()
{
    Counter c;
    
    ++c;
    ++c;
    ++c;
    
    return 0;
}

w5-1.cpp

//g++  5.4.0

#include <iostream>

class Friend {
    private:
    int friendValue;
    friend class Father;
        
    public:
    Friend(): friendValue(100) { }
};

class Father {
    protected:
    int getFriendValue(Friend f) {
        return f.friendValue;
    }
};

class Son: public Father {
    public:
    int getValue(Friend f) {
        return getFriendValue(f);
    }
};

int main()
{
    Friend f;
    Son s;
    std::cout << s.getValue(f) << std::endl;
}