我的题解
该题难度较低,最好写一下赋值构造函数,以及构造函数之间的初始化调用

#include<iostream>
#include<iomanip>
#include<string>
using namespace std;

class Person
{
    friend class Package;
    friend istream& operator>>(istream& c, Person& p);
    friend ostream& operator<<(ostream& c, Person p);
private:
    string name;
    string addr;
    string city;
    string state;
    int zipc;
public:
    //默认构造函数
    Person() :name(""), addr(""), city(""), state(""), zipc(0.0) {}
    //赋值构造函数
    Person(const Person& p)
    {
        name = p.name;
        addr = p.addr;
        city = p.city;
        state = p.state;
        zipc = p.zipc;
    }
};

class Package
{
protected:
    Person sed, rec;
    double weg, cos;
public:
    //初始化构造函数
    Package(Person a, Person b, double w, double c) :sed(a), rec(b), weg(w), cos(c) {}
    //赋值构造函数,调用初始化构造函数进行赋值
    Package(const Package& p) :Package(p.sed, p.rec, p.weg, p.cos) {}
    double calculateCost()
    {
        return weg * cos;
    }
    void print()
    {
        cout << sed << endl;
        cout << rec << endl;
    }
    bool check() {
        return weg > 0 && cos > 0;
    }
};

class TwoDayPackage : public Package
{
private:
    double ff;
public:
    double calculateCost()
    {
        return weg * cos + ff;
    }
    //调用package的赋值构造函数来初始化,下同
    TwoDayPackage(Package p, double f) : Package(p), ff(f) {}
};

class OvernightPackage :public Package
{
public:
    OvernightPackage(Package p, double f) : Package(p), ff(f) {}
    double calculateCost()
    {
        return weg * (cos + ff);
    }
private:
    double ff;
};

istream& operator>>(istream& c, Person& p)
{
    c >> p.name >> p.addr >> p.city >> p.state >> p.zipc;
    return c;
}

ostream& operator<<(ostream& c, Person p)
{
    c << p.name << ' ' << p.addr << ' ' << p.city << ' ' << p.state << ' ' << p.zipc;
    return c;
}

int main() {
    //录入收件人信息 
    Person sender;
    cin >> sender;

    //录入取件人信息
    Person recipient;
    cin >> recipient;

    //录入重量和单位重量的价格
    double weight;
    double price;
    cin >> weight;
    cin >> price;
    //创建Package实例
    Package p(sender, recipient, weight, price);
    //检测weight和price是否是正数
    if (!p.check()) {
        cout << "error" << endl;
        return 0;
    }

    //输入TwoDayPackage的固定费用
    double flatFee;
    cin >> flatFee;
    //创建 TwoDayPackage实例
    TwoDayPackage pTwoDay(p, flatFee);

    //输入OvernightPackage额外的单位重量收费
    double addFee;
    cin >> addFee;
    //创建 OvernightPackage实例
    OvernightPackage pOvernight(p, addFee);

    //打印发件人和收件人信息
    p.print();

    //打印 Package 收费
    cout << fixed << setprecision(3) << p.calculateCost() << endl;

    //打印 TwoDayPackage 收费 
    cout << fixed << setprecision(3) << pTwoDay.calculateCost() << endl;

    //打印 OvernightPackage 收费
    cout << fixed << setprecision(3) << pOvernight.calculateCost() << endl;

    return 0;
}