2023.4.24

//第9讲课件代码
#include <iostream>
using namespace std;
class CPolygon
{
protected:
    int width,height;
public:
    void set_values(int a,int b)
    {
        width = a;
        height = b;
    }
    virtual int area()
    {
        return (0);
    }
};
class CRectangle:public CPolygon
{
public:
    int area()
    {return(width*height);}
};
class CTriangle:public CPolygon
{
public:
    int area()
    {return (width*height)/2;}
};
int main()
{
    CRectangle rect;
    CTriangle trgl;
    CPolygon poly;
    CPolygon *ppoly;
    ppoly = &rect;
    ppoly->set_values(4,5);
    cout<<ppoly->area()<<endl;
    ppoly = &trgl;
    ppoly->set_values(4,5);
    cout<<ppoly->area()<<endl;
    return 0;
}