4.17

 求多边形的面积
 1 #include<iostream>
 2 using namespace std;
 3 class CPolygon{
 4 protected:
 5     int width,height;
 6 public:
 7     void set_values(int a,int b)
 8     {
 9         width=a;height=b;}
10 };
11 class CRectangle:public CPolygon{
12 public:
13     int area()
14     {return (width*height);}
15 };
16 class CTriangle:public CPolygon{
17 public:
18     int area()
19     {return (width*height/2);}
20 };
21 int main()
22 {
23     CRectangle rect;
24     CTriangle trgl;
25     rect.set_values(4,5);
26     trgl.set_values(4,5);
27     cout<<rect.area()<<endl;
28     cout<<trgl.area()<<endl;
29     return 0;
30 }