声明类Shape以及它的3个派生类：Circle、Square、Rectangle，用虚函数分别计算几种图形的面积、周长，编写程序，建立基类指针数组，每个指针均指向一个派生类对象，利用基类指针遍历元素对象，求取所有图形面积之和。请绘制UML类图。
1 //Shape.h
2 #ifndef _SHAPE_H_
3 #define _SHAPE_H_
4
5 class Shape
6 {
7 public:
8 virtual double S()=0;
9 virtual double C()=0;
10 };
11 #endif
12
13 //Circle.h
14 #include "Shape.h"
15
16 class Circle:public Shape
17 {
18 public:
19 Circle(double ir);
20 double S();
21 double C();
22 private:
23 double r;
24 };
25
26 //Circle.cpp
27 #include "Circle.h"
28 #include <iostream>
29 #define PI 3.14
30
31 using namespace std;
32
33 Circle::Circle(double ir)
34 {
35 r=ir;
36 cout<<"<construct a circle>"<<endl;
37 }
38 double Circle::S()
39 {
40 return (PI*r*r);
41 }
42 double Circle::C()
43 {
44 return (2*PI*r);
45 }
46
47 //Square.h
48 #include "Shape.h"
49
50 class Square:public Shape
51 {
52 public:
53 Square(double ia);
54 double S();
55 double C();
56 private:
57 double a;
58 };
59 //Square.cpp
60 #include "Square.h"
61 #include <iostream>
62
63 using namespace std;
64
65 Square::Square(double ia)
66 {
67 a=ia;
68 cout<<"<construct a square>"<<endl;
69 }
70 double Square::S()
71 {
72 return (a*a);
73 }
74 double Square::C()
75 {
76 return(4.0*a);
77 }
78
79 //Rectangle.h
80 #include "Shape.h"
81
82 class Rectangle:public Shape
83 {
84 public:
85 Rectangle(double iw,double ih);
86 double S();
87 double C();
88 private:
89 double w;
90 double h;
91 };
92
93 //Rectangle.cpp
94 #include "Rectangle.h"
95 #include <iostream>
96
97 using namespace std;
98
99 Rectangle::Rectangle(double iw,double ih)
100 {
101 w=iw;
102 h=ih;
103 cout<<"<construct a rectangle>"<<endl;
104 }
105 double Rectangle::S()
106 {
107 return (w*h);
108 }
109 double Rectangle::C()
110 {
111 return (2*(w+h));
112 }
113
114 //main.cpp
115 #include <iostream>
116 #include "Circle.h"
117 #include "Square.h"
118 #include "Rectangle.h"
119
120 using namespace std;
121
122 int main()
123 {
124 int i=0;
125 double c,s;
126 double sum=0;
127
128 Circle circle1(1);
129 Square square1(2);
130 Rectangle rectangle1(3,4);
131
132 Shape * p[3];
133 p[0]=&circle1;
134 p[1]=&square1;
135 p[2]=&rectangle1;
136
137 cout<<endl<<"Circle:"<<endl;
138 for(i=0;i<3;i++)
139 {
140 c=p[i]->C();
141 cout<<"c"<<i<<"="<<c<<endl;
142 }
143 cout<<endl<<"Square:"<<endl;
144 for(i=0;i<3;i++)
145 {
146 s=p[i]->S();
147 cout<<"s"<<i<<"="<<s<<endl;
148 sum+=s;
149 }
150 cout<<"total square="<<sum<<endl;
151 return 0;
152 }
1.error: redefinition of class Shape
使用宏定义防止头文件Shape.h被多次包含
#ifndef _SHAPE_H（有空格！否则unrecognized preprocessing directive：）
#define _SHAPE_H（有空格！）
class Shape {
//......
};
#endif
- 定义指针数组
类型 * p[n];