定义一个抽象基类Shape类，该类中包含一个double型的保护性数据成员area, ,然后分别实现如下功能:
- 在Shape类中定义一个虚析构函数 ；
- 在Shape类中定义一个纯虚函数Area()用于计算图形面积,定义一个虚函数Show()用于显示类中数据成员信息；
- 由Shape类采用公有继承派生出圆类（Circle）；在Circle类中新增公有的数据成员：半径（radious），圆心坐标点(x, y)；在该类中定义一个带有默认参数的初始化构造函数（默认参数值自拟）；编写Area()用于计算圆的面积；重写Show()函数，用于输出Circle类对象中所有的数据成员信息，并覆盖从基类中继承来的Show（）函数；
- 重载运算符“<<”，使之能输出Circle类对象（输出结果和show函数类似）；
- 重载运算符“+”，使之能计算两个圆的圆心间的距离(如圆a,b a+b 结果为两个圆心间距离)
- 由Shape类派生出矩形类（Rectangle）,在Rectangle类中新增私有的数据成员：边长width，height，编写Area()用于计算矩形的面积；重写Show()函数，用输出该类对象中所有的数据成员信息，覆盖从基类中继承来的Show()函数；
- 重载运算符“<<”重载，使之能输出Rectangle类对象；
- 在主函数中，分别声明两个Circle类对象，一个Rectangle类对象，调用各自对象的Area()函数求面积，对两个Circle类对象进行加法运算求圆心间距离，并输出圆心间距离；
- 在主函数中，声明Shape类指针变量一个，分别指向Circle类对象和Rectangle类对象, 分别调用该对象的Show()函数。
- 在主函数中，再动态建立一个Rectangle类对象，并调用其Area()函数和Show（）函数。
Shape.h
#include<iostream>
using namespace std;
class Shape
{
public:
Shape(){area = 0;}
virtual ~Shape(){
cout << "Shape的析构函数~" << endl;
}
virtual double Area() = 0;
virtual void Show();
protected :
double area;
};
class Circle: public Shape
{
public :
double radious;
double x, y;
Circle(){}
Circle(double, double, double);
~Circle(){
cout << "Circle的析构函数~" << endl;
}
virtual double Area();
virtual void Show();
friend ostream &operator << (ostream &, Circle &);
friend istream &operator >> (istream &, Circle &);
double operator +(Circle);
};
class Rectangle:public Shape{
public:
Rectangle(){}
Rectangle(double, double);
~Rectangle(){
cout << "Rectangle的析构函数~" << endl;
}
virtual double Area();
virtual void Show();
friend ostream &operator << (ostream &, Rectangle &);
friend istream &operator >> (istream &, Rectangle &);
private :
double width;
double height;
};Shape.cpp
#include<iostream>
#include<cstring>
#include<math.h>
#include"Shape.h"
using namespace std;
const double PI = 3.14159;
void Shape::Show(){
cout << "area is " << area << endl;
}
Circle::Circle(double a, double b, double r)
{
x = a;
y = b;
radious = r;
}
double Circle::operator +(Circle b){
double len;
double x = x - b.x;
double y = y - b.y;
len = x * x + y * y;
len = sqrt(len);
return len;
}
void Circle::Show(){
cout << "The Circle's radious is : " << radious << endl;
cout << "The Circle's center is : " ;
cout << "( " << x << "，" << y << " )"<< endl;
cout << "The Circle's area is : " << Area() << endl;
}
double Circle::Area(){
double area = PI * radious * radious;
return area;
}
istream& operator >>(istream &input, Circle& cir){
cout << "Please input the radious and " ;
cout << "Please input the center of Circle : ";
input >> cir.radious ;
input >> cir.x >> cir.y;
return input;
}
ostream& operator << (ostream & output, Circle& cir){
output << "The Circle's radious is : " << cir.radious << endl;
output << "The Circle's center is : " ;
output << "( " << cir.x << "，" << cir.y << " )"<< endl;
output << "The Circle's area is : " << cir.Area() << endl;
return output;
}
Rectangle::Rectangle(double w, double h){
width = w;
height = h;
}
double Rectangle::Area() {
area = width * height;
return area;
}
void Rectangle::Show(){
cout << "The Rectangle's width = " << width << endl;
cout << "The Rectangle's height = " << height << endl;
cout << "The Rectangle's area = " << Area() << endl;
}
ostream& operator <<(ostream& output, Rectangle& rec){
output << "The Rectangle's width = " << rec.width << endl;
output << "The Rectangle's height = " << rec.height << endl;
output << "The Rectangle's area = " << rec.area << endl;
}
istream& operator >>(istream& input, Rectangle& rec){
cout << "please input the rectangle's width and height : ";
input >> rec.width >> rec.height;
}Main.cpp
#include <iostream>
#include "Shape.h"
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main(){
Shape *pt = NULL;
Circle cir1(3, 5, 5), cir2(6, 2, 2);
double len;
Rectangle rec(5, 4);
len = cir1 + cir2;
cout << "Cir1's area = " << cir1.Area() << endl;
cout << "Cir2's area = " << cir2.Area() << endl;
cout << "cir1 与 cir2 圆心之间的距离为 ： " << len << endl;
cout << endl;
pt = &cir1;
pt->Show();
cout << endl;
pt = &rec;
pt->Show();
cout << endl;
Rectangle *r = new Rectangle(3, 4);
r->Area();
r->Show();
delete r;
return 0;
}