定义一个图形类(figure),其中有保护类型的成员数据：高度(height)和宽度(width)，一个公有的构造函数。由该图形类建立两个派生类：矩形类(rectangle)和等腰三角形类(triangle)。在每个派生类中都包含一个函数area（），分别用来计算矩形和等腰三角形的面积. 还有display()函数,显示对象的信息. 主函数如下: int main() { double width,height; cin>>width>>height; triangle tri(width,height); rectangle rect(width,height); tri.display(); cout<<"The area is "<<tri.area()<<endl; rect.display(); cout<<"The area is "<<rect.area()<<endl; return 0; } 【输入形式】宽度和高度 【输出形式】主函数输出，注意标点、空格

以下是代码实现：

#include <iostream>
using namespace std;

class Figure {
protected:
    double height;
    double width;
public:
    Figure(double h, double w): height(h), width(w) {}
    virtual double area() = 0;
    virtual void display() = 0;
};

class Rectangle: public Figure {
public:
    Rectangle(double h, double w): Figure(h, w) {}
    virtual double area() {
        return height * width;
    }
    virtual void display() {
        cout << "This is a rectangle with height " << height << " and width " << width << endl;
    }
};

class Triangle: public Figure {
public:
    Triangle(double h, double w): Figure(h, w) {}
    virtual double area() {
        return height * width * 0.5;
    }
    virtual void display() {
        cout << "This is a triangle with height " << height << " and width " << width << endl;
    }
};

int main() {
    double width, height;
    cin >> width >> height;
    Triangle tri(width, height);
    Rectangle rect(width, height);
    tri.display();
    cout << "The area is " << tri.area() << endl;
    rect.display();
    cout << "The area is " << rect.area() << endl;
    return 0;
}

输入格式：

3.4 4.5

输出格式：

This is a triangle with height 3.4 and width 4.5
The area is 7.65
This is a rectangle with height 3.4 and width 4.5
The area is 15.3