谭浩强《C--面向对象程序设计》第六章答案.docx

第六章
1:
//xt6-1/cpp
#include <iostream> //如用VC++应改为∶#include <iosttram.h>
using namespace std; //如用VC++应取消此行
#include "cylinder.h"
#include "point.cpp"
#include "circle.cpp"
#include "cylinder.cpp"
int main()
{Cylinder cy1(3.5,6.4,5.2,10);
cout<<"\noriginal cylinder:\nx="<<cy1.getX()<<", y="<<cy1.getY()<<", r="
<<cy1.getRadius()<<", h="<<cy1.getHeight()<<"\narea="<<cy1.area()
<<", volume="<<cy1.volume()<<endl;
cy1.setHeight(15);
cy1.setRadius(7.5);
cy1.setPoint(5,5);
cout<<"\nnew cylinder:\n"<<cy1;
Point &pRef=cy1;
cout<<"\npRef as a point:"<<pRef;
Circle &cRef=cy1;
cout<<"\ncRef as a Circle:"<<cRef;
return 0;
}
3:解法一
#include <iostream>
using namespace std;
class Point
{public:
Point(float a,float b):x(a),y(b){}
~Point(){cout<<"executing Point destructor"<<endl;}
private:
float x;
float y;
};

class Circle:public Point
{public:
Circle(float a,float b,float r):Point(a,b),radius(r){}
~Circle(){cout<<"executing Circle destructor"<<endl;}
private:
float radius;
};

int main()
{Point *p=new Circle(2.5,1.8,4.5);
delete p;
return 0;
}
3：解法二
#include <iostream>
using namespace std;
class Point
{public:
Point(float a,float b):x(a),y(b){}
~Point(){cout<<"executing Point destructor"<<endl;}
private:
float x;
float y;
};

class Circle:public Point
{public:
Circle(int a,int b,int r):Point(a,b),radius(r){}
~Circle(){cout<<"executing Circle destructor"<<endl;}
private:
float radius;
};

int main()
{Point *p=new Circle(2.5,1.8,4.5);
Circle *pt=new Circle(2.5,1.8,4.5);
delete pt;
return 0;
}
3：解法三
#include <iostream>
using namespace std;
class Point
{public:
Point(float a,float b):x(a),y(b){}
virtual ~Point(){cout<<"executing Point destructor"<<endl;}
private:
float x;
float y;
};

class Circle:public Point
{public:
Circle(float a,float b,float r):Point(a,b),radius(r){}
virtual ~Circle(){cout<<"executing Circle destructor"<<endl;}
private:
float radius;
};

void main()
{Point *p=new Circle(2.5,1.8,4.5);
delete p;
}
4：
#include <iostream>
using namespace std;
//定义抽象基类Shape
class Shape
{public:
virtual double area() const =0; //纯虚函数
};

//定义Circle类
class Circle:public Shape
{public:
Circle(double r):radius(r){} //结构函数
virtual double area() const {return 3.14159*radius*radius;}; //定义虚函数
protected:
double radius; //半径
};

//定义Rectangle类
class Rectangle:public Shape
{public:
Rectangle(double w,double h):width(w),height(h){} //结构函数
virtual double area() const {return width*height;} //定义虚函数
protected:
double width,height; //宽与高
};

class Triangle:public Shape
{public:
Triangle(double w,double h):width(w),height(h){} //结构函数
virtual double area() const {return 0.5*width*height;} //定义虚函数
protected:
double width,height; //宽与高
};

//输出面积的函数
void printArea(const Shape &s)
{cout<<s.area()<<endl;} //输出s的面积

int main()
{
Circle circle(12.6); //建立Circle类对象circle
cout<<"area of circle =";
printArea(circle); //输出circle的面积
Rectangle rectangle(4.5,8.4); //建立Rectangle类对象rectangle
cout<<"area of rectangle =";
printArea(rectangle); //输出rectangle的面积
Triangle triangle(4.5,8.4); //建立Triangle类对象
cout<<"area of triangle =";
printArea(triangle); //输出triangle的面积
return 0;
}
5：
#include <iostream>
using namespace std;
//定义抽象基类Shape
class Shape
{public:
virtual double area() const =0; //纯虚函数
};

//定义Circle(圆形)类
class Circle:public Shape
{public:
Circle(double r):radius(r){} //结构函数
virtual double area() const {return 3.14159*radius*radius;}; //定义虚函数
protected:
double radius; //半径
};

//定义Square(正方形)类
class Square:public Shape
{public:
Square(double s):side(s){} //结构函数
virtual double area() const {return side*side;} //定义虚函数
protected:
double side;
};

//定义Rectangle(矩形)类
class Rectangle:public Shape
{public:
Rectangle(double w,double h):width(w),height(h){} //结构函数
virtual double area() const {return width*height;} //定义虚函数
protected:
double width,height; //宽与高
};

//定义Trapezoid(梯形)类
class Trapezoid:public Shape
{public:
Trapezoid(double t,double b,double h):top(t),bottom(t),height(h){} //结构函数
virtual double area() const {return 0.5*(top+bottom)*height;} //定义虚函数
protected:
double top,bottom,height; //上底、下底与高
};

//定义Triangle(三角形)类
class Triangle:public Shape
{public:
Triangle(double w,double h):width(w),height(h){} //结构函数
virtual double area() const {return 0.5*width*height;} //定义虚函数
protected:
double width,height; //宽与高
};

int main()
{
Circle circle(12.6); //建立Circle类对象circle
Square square(3.5); //建立Square类对象square
Rectangle rectangle(4.5,8.4); //建立Rectangle类对象rectangle
Trapezoid trapezoid(2.0,4.5,3.2); //建立Trapezoid类对象trapezoid
Triangle triangle(4.5,8.4); //建立Triangle类对象
Shape *pt[5]={&circle,&square,&rectangle,&trapezoid,&triangle};
//定义基类指针数组pt，使它每一个元素指向一个派生类对象
double areas=0.0; //areas为总面积
for(int i=0;i<5;i++)
{areas=areas+pt[i]->area();}
cout<<"totol of all areas="<<areas<<endl; //输出总面积
return 0;
}