pta程序设计类实验辅助教学平台-练习题

定义抽象基类Shape，由它派生出五个派生类：Circle（圆形）、Square（正方形）、Rectangle（ 长方形）、Trapezoid （梯形）和Triangle （三角形），用虚函数分别计算各种图形的面积，并求出它们的和。要求用基类指针数组。使它的每一个元素指向一个派生类的对象。PI=3.1415926。

 1 #include <iostream>
 2 #define PI 3.1415926
 3 using namespace std;
 4 class Shape
 5 {
 6     public:
 7     virtual double area()=0;
 8 };
 9 class Circle:public Shape
10 {
11     private:
12     double r;
13     public:
14     Circle(double x):r(x){}
15     double area()
16     {
17     return PI*r*r;
18     }
19 };
20 class Square:public Shape
21 {
22     private:
23     double x;
24     public:
25     Square(double a):x(a){}
26     double area()
27     {
28     return x*x;
29     }
30 };
31 class Rectangle:public Shape
32 {
33     private:
34     double x;
35     double y;
36     public:
37     Rectangle(double a,double b):x(a),y(b){}
38     double area()
39     {
40     return x*y;
41     }
42 };
43 class Trapezoid:public Shape
44 {
45     private:
46     double x;
47     double y;
48     double z;
49     public:
50     Trapezoid(double a,double b,double c):x(a),y(b),z(c){}
51     double area()
52     {
53     return (x+y)*z/2;
54     }
55 };
56 class Triangle:public Shape
57 {
58     private:
59     double x;
60     double y;
61     public:
62     Triangle(double a,double b):x(a),y(b){}
63     double area()
64     {
65     return x*y/2;
66     }
67 };
68 int main()
69 {
70     Shape* Shapes[5];
71     double a,b,c,d,e,f,g,h,i;
72     cin>>a>>b>>c>>d>>e>>f>>g>>h>>i;
73     Shapes[0]=new Circle(a);
74     Shapes[1]=new Square(b);
75     Shapes[2]=new Rectangle(c,d);
76     Shapes[3]=new Trapezoid(e,f,g);
77     Shapes[4]=new Triangle(h,i);
78     double sum;
79     sum=Shapes[0]->area()+Shapes[1]->area()+Shapes[2]->area()+Shapes[3]->area()+Shapes[4]->area();
80     cout<<"total of all areas = "<<sum<<endl;
81 }