#include<iostream> #include<string> using namespace std; class A { protected: string m; double p; public: A(const string& a = "", double b = 0) { m = a; p = b; } string getM() { return m; } double getP() { return p; } virtual void Show() { cout << m << "," << p << endl; } }; class B :public A{ int s; public: B(const string& a, double b, int c = 3) { s = c; } void Show() { cout << m << "," << p << "," << s<<endl; } friend int operator+(B&, B&); }; int operator+(B& b1, B& b2) { return b1.s + b2.s; } int main() { B s1("hhh",300), s2("yyy", 2400, 2); s1.Show(); A& f = s1; f.Show(); cout << f.getM() << "," << f.getP() << endl; cout << s2.getM() << "," << s2.getP() << endl; cout << s1 + s1 << endl; }

这段代码定义了两个类 A 和 B，其中 B 继承自 A，A 中有两个数据成员 m 和 p，表示名称和价格，有一个虚函数 Show()，用于输出对象的名称和价格；B 中有一个数据成员 s，表示数量，也有一个 Show() 函数，输出对象的名称、价格和数量。B 中还重载了一个 + 运算符，用于计算两个 B 对象的数量之和。

在 main 函数中，定义了两个 B 对象 s1 和 s2，分别传入不同的参数进行初始化。然后分别调用它们的 Show() 函数进行输出。接着定义了一个 A 类型的引用 f，指向 s1 对象，并调用 f 的 Show() 函数进行输出。然后分别输出 s2 对象的名称和价格。最后调用了 s1 + s1，输出两个对象数量之和。

相关问题

#include<iostream> using namespace std; class Shape { public: virtual double area() const=0; }; class Circle:public Shape { public: Circle(double r):radius(r) { } virtual double area() const { return 3.14159*radius*radius; } protected: double radius; }; class Square:public Shape { public: Square(double s):side(s) { } virtual double area() const { return side*side; } protected: double side; }; class Rectangle:public Shape { public: Rectangle(double w,double h):width(w),height(h) { } virtual double area() const { return width*height; } protected: double width,height; }; class Trapezoid:public Shape { public: Trapezoid(double t,double b,double h):top(t),bottom(b),height(h) { } virtual double area() const { return 0.5*(top+bottom)*height; } protected: double top,bottom,height; }; class Triangle:public Shape { public: Triangle(double w,double h):width(w),height(h) { } virtual double area() const { return 0.5*width*height; } protected: double width,height; }; int main() { Circle circle(12.6); Square square(3.5); Rectangle rectangle(4.5,8.4); Trapezoid trapezoid(2.0,4.5,3.2); Triangle triangle(4.5,8.4); Shape *pt[5]= { &circle,&square,&rectangle,&trapezoid,&triangle }; double areas=0.0; for(int i=0; i<5; i++) { areas=areas+pt[i]->area(); } cout<<"total of all areas="<<areas<<endl; return 0; }这段代码若要输出Circle:498.51 Square:12.25 Rectangle:37.80 Trapezoid:10.40 Triangle:18.90，如何改进

可以将输出语句放在循环中，分别输出每个图形的面积。可以在每个 Shape 类的子类中添加一个成员函数，用于返回该图形的名称，然后在输出语句中使用该函数获取图形名称。代码如下：

#include<iostream>
using namespace std;

class Shape {
public:
    virtual double area() const = 0;
    virtual string name() const = 0; // 添加获取图形名称的函数
};

class Circle : public Shape {
public:
    Circle(double r) : radius(r) {}
    virtual double area() const {
        return 3.14159 * radius * radius;
    }
    virtual string name() const { // 返回图形名称
        return "Circle";
    }
protected:
    double radius;
};

class Square : public Shape {
public:
    Square(double s) : side(s) {}
    virtual double area() const {
        return side * side;
    }
    virtual string name() const {
        return "Square";
    }
protected:
    double side;
};

class Rectangle : public Shape {
public:
    Rectangle(double w, double h) : width(w), height(h) {}
    virtual double area() const {
        return width * height;
    }
    virtual string name() const {
        return "Rectangle";
    }
protected:
    double width, height;
};

class Trapezoid : public Shape {
public:
    Trapezoid(double t, double b, double h) : top(t), bottom(b), height(h) {}
    virtual double area() const {
        return 0.5 * (top + bottom) * height;
    }
    virtual string name() const {
        return "Trapezoid";
    }
protected:
    double top, bottom, height;
};

class Triangle : public Shape {
public:
    Triangle(double w, double h) : width(w), height(h) {}
    virtual double area() const {
        return 0.5 * width * height;
    }
    virtual string name() const {
        return "Triangle";
    }
protected:
    double width, height;
};

int main() {
    Circle circle(12.6);
    Square square(3.5);
    Rectangle rectangle(4.5, 8.4);
    Trapezoid trapezoid(2.0, 4.5, 3.2);
    Triangle triangle(4.5, 8.4);
    Shape* pt[] = { &circle,&square,&rectangle,&trapezoid,&triangle };
    double areas = 0.0;
    for (int i = 0; i < 5; i++) {
        cout << pt[i]->name() << ":" << pt[i]->area() << " "; // 输出图形名称和面积
        areas += pt[i]->area();
    }
    cout << endl << "total of all areas=" << areas << endl;
    return 0;
}

#include<iostream> #include<string> using namespace std; class Pet { protected: string name; int age; double weight; public: //Pet(string name,int age,float weight) // { // this->name=name; //this->age=age; //this->weight=weight; // } Pet() { name=""; age=0; weight=0.0; } Pet(const string&petName,int petAge,double petWeight) { name = petName; age = petAge; weight = petWeight; } string getName() { return name; } int getAge() { return age; } double getWeight() { return weight; } void setName(string name) { this->name=name; } void setAge(int age) { this->age=age; } void setWeight(double weight) { this->weight=weight; } virtual string getLifespan() { return "unknown lifespan"; } }; class Dog:public Pet { private: string breed; public: Dog(string name,int age,double weight,string breed) : Pet(name,age,weight) { this->breed=breed; } string getBreed() { return breed; } void setBreed(string breed) { this->breed=breed; } virtual string getLifespan() { if (weight>100) { return "Approximately 7 years"; } else { return "Approximately 13 years"; } } }; class Rock:public Pet { public: Rock(string name,int age,double weight) : Pet(name,age,weight) {} virtual string getLifespan() { return"Thousands of years"; } }; int main() { Pet*pet1=new Rock("Peter",1000,1000); Pet*pet2=new Dog("Mike",3,80,"Golden Retriever"); Pet*pet3=new Dog("Ham",5,80,"Labrador Retriever"); cout<<pet1->getName()<<", "<<pet1->getLifespan()<< endl; pet1->setAge(2); pet1->setWeight(1.0); cout<<pet2->getName()<<"," <<pet2->getLifespan()<<endl; cout<<"Breed: "<pet2->getBreed()<<endl; pet2->setWeight(85.0); cout<<pet3->getName()<<"," <<pet3->getLifespan()<<endl; cout<<"Breed: "<<pet3->getBreed() <<endl; pet3->setWeight(110.0); return 0; } 这段代码无法运行

这段代码其实是可以运行的，但是存在一些小问题。首先，代码开头的 `#include` 需要在每一行的末尾添加一个分号，例如 `#include<iostream>;`。其次，`Pet` 类中的构造函数不应该被注释掉，因为在 `Rock` 和 `Dog` 类中都需要调用它来初始化基类的成员变量。最后，`main` 函数中输出狗的品种时，应该使用 `cout<<"Breed: "<<pet2->getBreed()<<endl;` 和 `cout<<"Breed: "<<pet3->getBreed()<<endl;`，而不是使用两个 `<` 符号。