题目：
1、声明Point（点）类，由Point类派生出Circle（圆）类，再由Circle类派生出Cylinder（圆柱）类。将类的定义部分分别作为3个头文件。对它们的成员函数的声明部分分别作为3个源文件（.cpp文件），在主函数中用#include命令把它们包含进来。形成一个完整的程序，并上机运行。
2、教材第12章例12.3的基础上作以下修改。
*把构造函数修改为带参数的函数，在建立对象时初始化。
*先不要析构函数声明virtual，在main函数中另设一个指向Circle类对象的指针变量。使它指向gradl。运行程序，分析结果。
*不作第2点的修改而将析构函数声明为virtual，运行程序，分析结果。
3、声明抽象基类shape, 由它派生出3个派生类：Circle（圆形）、Rectangle（矩形）、Triangle（三角形），用一个函数printArea分别输出以上三者的面积，3个图形的数据在定义对象时给定。
参考代码：
1、
#ifndef _Circle_H//Circle.h
#define _Circle_H
#include<iostream.h>
class Circle:public Point{
protected:
double radius;
public:
Circle(double =0,double =0,double =0);
friend ostream & operator<<(ostream &,const Circle &);
void setRadius(double);
double getRadius()const;
double area()const;
};
#endif
#ifndef _Cylinder_H//Cylinder.h
#define _Cylinder_H
#include<iostream.h>
class Cylinder:public Circle{
private:
double height;
public:
Cylinder(double=0,double=0,double=0,double=0);
void setHeight(double);
double getHeight()const;
double area()const;
double volume()const;
friend ostream & operator<<(ostream &,const Cylinder &);
};
#endif
#ifndef _Point_H//Point.h
#define _Point_H
#include<iostream.h>
class Point{
protected:
double x;
double y;
public:
Point(double=0,double=0);
void setPoint(double,double);
double getX();
double getY();
friend ostream & operator<<(ostream &,const Point &);
};
#endif
#include"Point.h"//Circle.cpp
#include"Circle.h"
#include<iostream.h>
Circle::Circle(double a ,double b ,double c ):Point(a,b){
radius=c;
}
void Circle::setRadius(double a){
radius = a;
}
double Circle::getRadius()const{
return radius;
}
double Circle::area()const{
return 3.14*radius*radius;
}
ostream &operator<<(ostream &output,const Circle &c){
output<<c.area()<<endl;
return output;
}
#include"Point.h"//Cylinder.cpp
#include"Circle.h"
#include"Cylinder.h"
#include<iostream.h>
Cylinder::Cylinder(double a,double b,double c,double d):Circle(a,b,c){
height = d;
}
void Cylinder::setHeight(double a){
height = a;
}
double Cylinder::getHeight ()const{
return height;
}
double Cylinder::area()const{
return 2*Circle::area()+height*2*3.14*radius;
}
double Cylinder::volume()const{
return Circle::area() *height;
}
ostream &operator<<(ostream & output,const Cylinder & cy){
cout<< "修改x，y为[" << cy.x << "," << cy.y << "],r=" << cy.radius <<",h"<<cy.height << "\n" <<"表面积=" <<cy.area () << ",体积=" <<cy.volume () <<endl;
return output;
}
#include"Point.h"//Point.cpp
#include<iostream.h>
Point::Point(double a,double b){
x = a;
y = b;
}
void Point::setPoint(double a,double b){
x = a;
y = b;
}
double Point::getX(){
return x;
}
double Point::getY(){
return y;
}
ostream & operator<<(ostream &output,const Point &p){
output<<"["<<p.x<<","<<p.y<<"]"<<endl;
return output;
}
#include"Point.h"//Main.cpp
#include"Circle.h"
#include"Cylinder.h"
#include<iostream.h>
int main(){
Cylinder cy1(3.5,6.4,5.2,10);
cout<< "圆柱:\nx=" << cy1.getX() << ",y=" << cy1.getY() << ",r=" << cy1.getRadius() << ",h=" << cy1.getHeight () << "\n" << "表面积=" << cy1.area() << ",体积=" << cy1.volume () << endl;
cy1.setHeight (15);
cy1.setRadius (7.5);
cy1.setPoint(5,5);
cout<<endl;
cout<< "新圆柱:\n" <<cy1;
Point &pRef = cy1;
cout<< "\n"<<"x,y为" <<pRef;
Circle &cRef = cy1;
cout<< "\n"<<"圆的面积为" <<cRef;
return 0;
}
2、
#include<iostream>
using namespace std;
class Point{
public:
Point(){}
virtual~Point(){
cout<<"execyting Point destructor" <<endl;
}
};
class Cricle:public Point{
public:
Cricle(int = 0);
virtual~Cricle(){
cout<< "exceuting Circle destructor" << endl;
}
private:
int radus;
};
Cricle::Cricle(int a){
radus = a;
}
int main(){
Point *p=new Cricle(33);
// Cricle *c=new Cricle(33); //第二小问
// delete c; //第二小问
delete p;
return 0;
}
3、
#include<iostream>
using namespace std;
class shape{
public:
virtual double area()=0;
};
class Circle:public shape{
public:
Circle(double a){
r=a;
}
virtual double area(){
return r*r*3.14;
}
protected:
double r;
};
class Rectangle:public shape{
public:
Rectangle(double a,double b){
x=a;y=b;
}
virtual double area(){
return x*y;
}
protected:
double x,y;
};
class Triangle:public shape{
public:
Triangle(double a,double b){
d=a;
g=b;
}
virtual double area(){
return d*g/2;
}
protected:
double d;
double g;
};
void printArea(Circle &c1,Rectangle &r1,Triangle &t1){
cout<<"圆的面积："<<c1.area()<<'\n'<<"矩形面积："<<r1.area() <<'\n'<<"三角形面积："<<t1.area ()<<endl;
}
int main(){
void printArea(Circle &,Rectangle &,Triangle &);
Circle c1(3.0);
Rectangle r1(2.1,3.0);
Triangle t1(2.2,3.3);
printArea(c1,r1,t1);
return 0;
}
