C++第六章

1. #include <iostream.h>class Point{public:Point(float x=0,float y=0);void setPoint(float,float);float getX() const{return x;}float getY() const{return y;}friend ostream & operator<<(ostream &output,Point &);protected:float x,y;};Point::Point(float a,float b){x=a;y=b;}void Point::setPoint(float a,float b){ x=a;y=b;}ostream & operator<<(ostream &output,Point &p){ output<<"["<<p.x<<","<<p.y<<"]"<<endl; return output;}class Circle:public Point{public:Circle(float x,float y,float r):Point(x,y),radius(r){}void setRadius(float r){radius=r;}float getRadius() const{return radius;}double area() const{ return 3.1415*radius*radius;}friend ostream & operator<<(ostream &output,Circle &);protected:float radius;};ostream & operator<<(ostream &output,Circle &c){output<<"Center =["<<c.x<<","<<c.y<<"],r= "<<c.radius<<",area="<<c.area()<<endl;return output;}class Cylinder:public Circle{public:Cylinder(float x,float y,float r,float h):Circle(x,y,r),height(h){}void setHeight(float h){height=h;}float getHeight() const{return height;}double area() const{return 2*Circle::area()+2*3.1415*radius*height; }double volume() const{    return 3.1415*radius*radius*height;}friend ostream & operator<<(ostream &output,Cylinder &);protected:float height;};ostream & operator<<(ostream &output,Cylinder &cy){ output<<"Center=["<<cy.x<<cy.y<<"],r="<<cy.radius<<",h="<<cy.height<<"\narea="<<cy.area()<<",volume="<<cy.volume()<<endl; return output;}int main(){ Cylinder cy1(3.5,6.4,5.2,10); cout<<"original 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;}

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3.(1) #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(1,2,3); delete p; return 0;}

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(2)#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(1,2,3); Circle *r=new Circle(1,2,3); delete r; return 0;}

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(3) #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){}~Circle(){cout<<"executing Circle destructor"<<endl;}private:float radius;};int main(){ Point *p=new Circle(1,2,3); delete p; return 0;}

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4. #include <iostream.h>class Shape{public:virtual double area()const =0;};class Circle:public Shape{public:Circle(double r):radius(r){}virtual double area() const{ return 3.1415*radius*radius;}protected:double radius;};class Rectangle :public Shape{public:Rectangle(double l,double w):length(l),width(w){}virtual double area()const{ return length*width;}protected:double length;double width;};class Triangle:public Shape{public:Triangle(double d,double h):dibian(d),height(h){}virtual double area() const{ return 0.5*dibian*height;}protected:double dibian;double height;};void display(const Shape &s){ cout<<s.area()<<endl;}int main(){ Circle c(4); cout<<"area of c is "; display(c); Rectangle r(2,4); cout<<"area of r is "; display(r); Triangle t(1,2); cout<<"area of t is "; display(t); return 0;}

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5. #include <iostream.h>class Shape{public:virtual double area()const =0;};class Circle:public Shape{public:Circle(double r):radius(r){}virtual double area() const{ return 3.1415*radius*radius;}protected:double radius;};class Rectangle :public Shape{public:Rectangle(double l,double w):length(l),width(w){}virtual double area()const{ return length*width;}protected:double length;double width;};class Triangle:public Shape{public:Triangle(double d,double h):dibian(d),height(h){}virtual double area() const{ return 0.5*dibian*height;}protected:double dibian;double height;};class Square:public Shape{public:Square(double s):side(s){}virtual double area() const{ return side*side;}protected:double side;};class Trapezoid:public Shape{public:Trapezoid(double t,double b,double h):top(t),bottem(b),height(h){}virtual double area() const{ return 0.5*(top+bottem)*height;}protected:double top,bottem,height;};void display(const Shape &s){ cout<<s.area()<<endl;}int main(){ Circle c(4); Rectangle r(2,4); Triangle t(1,2); Square s(2); Trapezoid tt(1,2,3); Shape *p[5]={&c,&r,&t,&s,&tt}; double area=0.0; for(int i=0;i<5;i++) {  area=area+p[i]->area(); } cout<<"the sum of area is "<<area<<endl; return 0;}

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