C++中的多态和虚函数

#include <iostream>
    using namespace std;
    //基类People
    class People{
    public:
        People(char *name, int age);
        void display();
    protected:
        char *m_name;
        int m_age;
    };
    People::People(char *name, int age): m_name(name), m_age(age){}
    void People::display(){
        cout<<m_name<<"今年"<<m_age<<"岁了，是个无业游民。"<<endl;
    }
    //派生类Teacher
    class Teacher: public People{
    public:
        Teacher(char *name, int age, int salary);
        void display();
    private:
        int m_salary;
    };
    Teacher::Teacher(char *name, int age, int salary): People(name, age), m_salary(salary){}
    void Teacher::display(){
        cout<<m_name<<"今年"<<m_age<<"岁了，是一名教师，每月有"<<m_salary<<"元的收入。"<<endl;
    }
    int main(){
        People *p = new People("王志刚", 23);
        p -> display();
        p = new Teacher("赵宏佳", 45, 8200);
        p -> display();
        return 0;
    }

#include <iostream>
    using namespace std;
    //基类People
    class People{
    public:
        People(char *name, int age);
        virtual void display();  //声明为虚函数
    protected:
        char *m_name;
        int m_age;
    };
    People::People(char *name, int age): m_name(name), m_age(age){}
    void People::display(){
        cout<<m_name<<"今年"<<m_age<<"岁了，是个无业游民。"<<endl;
    }
    //派生类Teacher
    class Teacher: public People{
    public:
        Teacher(char *name, int age, int salary);
        virtual void display();  //声明为虚函数
    private:
        int m_salary;
    };
    Teacher::Teacher(char *name, int age, int salary): People(name, age), m_salary(salary){}
    void Teacher::display(){
        cout<<m_name<<"今年"<<m_age<<"岁了，是一名教师，每月有"<<m_salary<<"元的收入。"<<endl;
    }
    int main(){
        People *p = new People("王志刚", 23);
        p -> display();
        p = new Teacher("赵宏佳", 45, 8200);
        p -> display();
        return 0;
    }

int main(){
        People p("王志刚", 23);
        Teacher t("赵宏佳", 45, 8200);
        People &rp = p;
        People &rt = t;
        rp.display();
        rt.display();
        return 0;
    }

#include <iostream>
    using namespace std;
    //军队
    class Troops{
    public:
        virtual void fight(){ cout<<"Strike back!"<<endl; }
    };
    //陆军
    class Army: public Troops{
    public:
        void fight(){ cout<<"--Army is fighting!"<<endl; }
    };
    //99A主战坦克
    class _99A: public Army{
    public:
        void fight(){ cout<<"----99A(Tank) is fighting!"<<endl; }
    };
    //武直10武装直升机
    class WZ_10: public Army{
    public:
        void fight(){ cout<<"----WZ-10(Helicopter) is fighting!"<<endl; }
    };
    //长剑10巡航导弹
    class CJ_10: public Army{
    public:
        void fight(){ cout<<"----CJ-10(Missile) is fighting!"<<endl; }
    };
    //空军
    class AirForce: public Troops{
    public:
        void fight(){ cout<<"--AirForce is fighting!"<<endl; }
    };
    //J-20隐形歼击机
    class J_20: public AirForce{
    public:
        void fight(){ cout<<"----J-20(Fighter Plane) is fighting!"<<endl; }
    };
    //CH5无人机
    class CH_5: public AirForce{
    public:
        void fight(){ cout<<"----CH-5(UAV) is fighting!"<<endl; }
    };
    //轰6K轰炸机
    class H_6K: public AirForce{
    public:
        void fight(){ cout<<"----H-6K(Bomber) is fighting!"<<endl; }
    };
    int main(){
        Troops *p = new Troops;
        p ->fight();
        //陆军
        p = new Army;
        p ->fight();
        p = new _99A;
        p -> fight();
        p = new WZ_10;
        p -> fight();
        p = new CJ_10;
        p -> fight();
        //空军
        p = new AirForce;
        p -> fight();
        p = new J_20;
        p -> fight();
        p = new CH_5;
        p -> fight();
        p = new H_6K;
        p -> fight();
        return 0;
    }