c++ 子类虚函数、友元函数、复构、构造、赋值=的重写方式 - 练习题

#include <iostream>
#include <cstring>
using namespace std;

class Port{
private:
	char* brand;
	char style[20];
	int bottles;
public:
	Port(const char* br="none", const char*st="none", int b=0){
		brand = new char[strlen(br)+1];
		strcpy(brand,br);
		strcpy(style,st);
		bottles = b;
	}
	Port(const Port&p){
		brand = new char[strlen(p.brand)+1];
		strcpy(brand, p.brand);
		strcpy(style, p.style);
		bottles = p.bottles;
	}
	virtual ~Port(){delete[] brand;}
	Port& operator=(const Port&p){
		if(&p==this)
			return *this;
		delete[] brand;
		brand = new char[strlen(p.brand)+1];
		strcpy(brand, p.brand);
		strcpy(style, p.style);
		bottles = p.bottles;
		return *this;
	}
	Port& operator+=(int b){
		bottles += b;
		return *this;
	}
	Port& operator-=(int b){
		bottles -= b;
		bottles = bottles>0?bottles:0;
		return *this;
	}

	int BottleConut() const{return bottles;}
	virtual void show() const{
		cout<<"Brand: "<<brand<<endl<<"Kind: "<<style<<endl<<"Bottles: "<<bottles<<endl;
	}
	friend ostream& operator<<(ostream&os, const Port&p){
		os<<p.brand<<", "<<p.style<<", "<<p.bottles;
		return os;
	}
};


class VintagePort: public Port{
private:
	char* nickname;
	int year;
public:
	VintagePort():Port("none","vintage",0),year(0) //可使用初始化列表
	{
		nickname = new char[strlen("none")+1];
		strcpy(nickname, "none");
	}
	VintagePort(const char* br, int b, const char *nn, int y){
		Port::Port(br,"vintage",b); // 构造函数的重写方式
		nickname = new char[strlen(nn)+1];
		strcpy(nickname, nn);
		year = y;
	}
	VintagePort(const VintagePort& vp):Port(vp){
		nickname = new char[strlen(vp.nickname)+1];
		strcpy(nickname, vp.nickname);
		year = vp.year;
	}
	~VintagePort(){delete[] nickname;}
	VintagePort& operator=(const VintagePort&vp){
		if(&vp==this)
			return *this;
		delete[] nickname;
		Port::operator=(vp); // 赋值=的重写方式
		nickname = new char[strlen(vp.nickname)+1];
		strcpy(nickname, vp.nickname);
		year = vp.year;
		return *this;
	}
	virtual void show() const{
		Port::show(); // 虚函数重写，需要调用基本虚函数时
		cout<<"Nickname: "<<nickname<<endl<<"Year: "<<year<<endl;
	}
	friend ostream& operator<<(ostream&os, const VintagePort&vp){
		os<<(const Port&)vp; // 友元函数的重写方式
		os<<", "<<vp.nickname<<", "<<vp.year;
		return os;
	}

};