#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;
}