Question

设计一个图形类Shape，其中包含两个纯虚函数:输出函数disp()和求面积函数area()

设计一个图形类Shape，其中包含两个纯虚函数:输出函数disp()和求面积函数area()，然后派生出二维图形类TwoDShape和三维图形类ThreeDShape，均包含各自的虚函数求周长函数perimeter()和求体积函数volume(),之后由TwoDShape派生出圆类Circle和矩形类Rectangle,由ThreeDShape派生出柱体类Cone和正方体类Box，最后在主函数中通过抽象基类实现统一接口。

Answer 1

#include "stdafx.h"
#include<iostream>

using namespace std;

const double PI = 3.14;

class Shape
{
public:
virtual void disp() = 0;
virtual double area() = 0;
};

class TwoDShape:public Shape
{
public:
virtual double perimeter(){ return 0; }
};

class ThreeDShape:public Shape
{
public:
virtual double volume(){ return 0; }
};

class Circle: public TwoDShape
{
private:
double radius;
public:
Circle(double r = 0):radius(r){}
double perimeter() { return 2 * PI * radius; }
double area(){return PI*radius*radius;}
void disp(){cout << "Circle : radius = " << radius << endl;}
};

class Rectangle: public TwoDShape
{
private:
double length;
double width;
public:
Rectangle(double l=0, double w = 0):length(l), width(w){}
double perimeter(){return 2 * (length + width);}
double area() {return length * width;}
void disp(){cout << "Rectangle : length = " << length << ", width = "<< width << endl;}
};

class Cone: public ThreeDShape
{
private:
double radius;
double high;
public:
Cone(double r=0, double h = 0):radius(r), high(h){}
double volume(){return PI*radius*radius*high;}
double area() {return 2*PI*radius*(2+high);}
void disp(){cout << "Cone : radius = " << radius << ", high = "<< high << endl;}
};

class Box: public ThreeDShape
{
private:
double length;
public:
Box(double l=0):length(l){}
double volume(){return length*length*length;}
double area() {return 6*length*length;}
void disp(){cout << "Box : length = " << length << endl;}
};

void main(int argc, char *argv[])
{
Circle circle(5);
Rectangle rect(4,6);
Cone cone(3, 2);
Box box(7);

Shape* ptr = &circle;
ptr->disp();
cout << ptr->area() << endl;

ptr = ▭
ptr->disp();
cout << ptr->area() << endl;

ptr = &cone;
ptr->disp();
cout << ptr->area() << endl;

ptr = &box;
ptr->disp();
cout << ptr->area() << endl;
}