【C++】第11章作业

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三个选择题

Shape类的继承

【问题描述】定义一个Shape基类，在此基础上派生出Rectangle和Circle类，二者都有GetArea（）函数计算对象的面积,使用Rectangle类创建一个派生类Square。并应用相应类的对象测试。【注意：π取3.14】

【输入形式】三种形状基本数据。

【输出形式】对应每种形状的面积。

【样例说明】第一行的数据为基本数据（四个），分别为圆形半径，长方形长和宽，正方形边长。

#include<iostream>
using namespace std;
class Shape { 
public: 
Shape(){}  
~Shape(){} 
virtual float GetArea() {return -1;} 
}; 
class Circle :public Shape 
{
private:
    float r;
public:
    Circle(float rr):r(rr){}
    virtual  float  GetArea()
    {
        return (3.14*r*r);
    }  
};
class Rectangle:public Shape 
{
protected:
    float l,h;
public:
    Rectangle(float ll,float hh):l(ll),h(hh){}
    virtual  float  GetArea()
    {
        return (l*h);
    }
};
class Square: public Rectangle
{
public:
    Square(float ss):Rectangle(ss,ss){}
    virtual  float  GetArea()
    {
        return (h*l);
    }
};
int main() 
{ 
Shape *sp; 
int radium,length,hight,side;
cin>>radium>>length>>hight>>side;
sp=new Circle(radium); 
cout<<"The area of the circle is "<<sp->GetArea()<<endl;   
sp=new Rectangle(length,hight); 
cout<<"The area of the rectangle is "<<sp->GetArea()<<endl;   
sp=new Square(side); 
cout<<"The area of the Square is "<<sp->GetArea()<<endl;
delete sp;
return 0;
}