2023.4.24

 1 //第9讲课件代码
 2 #include <iostream>
 3 using namespace std;
 4 class CPolygon
 5 {
 6 protected:
 7     int width,height;
 8 public:
 9     void set_values(int a,int b)
10     {
11         width = a;
12         height = b;
13     }
14     virtual int area()
15     {
16         return (0);
17     }
18 };
19 class CRectangle:public CPolygon
20 {
21 public:
22     int area()
23     {return(width*height);}
24 };
25 class CTriangle:public CPolygon
26 {
27 public:
28     int area()
29     {return (width*height)/2;}
30 };
31 int main()
32 {
33     CRectangle rect;
34     CTriangle trgl;
35     CPolygon poly;
36     CPolygon *ppoly;
37     ppoly = &rect;
38     ppoly->set_values(4,5);
39     cout<<ppoly->area()<<endl;
40     ppoly = &trgl;
41     ppoly->set_values(4,5);
42     cout<<ppoly->area()<<endl;
43     return 0;
44 }