Question

用C++编写一个程序,定义抽象基类Shape，由它派生出５个派生类：Cricle（圆形),Squa

用C++编写一个程序,定义抽象基类Shape，由它派生出５个派生类：Cricle（圆形),Square（正方形)， Rectangle（矩形）， Trapezoid （梯形）,Triangle（三角形）。用虚函数分别计算图形面积，并求所有图形面积的和．要求用基类指针数组，使它的每一个元素指向一个派生类对象。

Answer 1

#include <iostream>
using namespace std;

class Shape //定义抽象基类 Shape
{
public:
virtual double area() const =0; //纯虚函数
};

class Circle:public Shape
{
public:
Circle(double r):radius(r){} //构造函数

virtual double area() const //定义虚函数
{
return 3.14159*radius*radius;
};
protected:
double radius;
};

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

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

class Trapezoid:public Shape //定义 Trapezoid(梯形)类
{
public:
Trapezoid(double t,double b,doubleh):top(t),bottom(t),height(h){} //构造函数
virtual double area() const {return0.5*(top+bottom)*height;} //定义虚函数
protected:
double top,bottom,height;//上底、下底与高
};
class Triangle:public Shape//定义 Triangle(三角形)类
{
public:
Triangle(double w,double h):width(w),height(h){}//构造函数
virtual double area() const {return 0.5*width*height;} //定义虚
protected:
double width,height;
};

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;
}

Answer 2

#include <iostream>

using namespace std;
class Shape
{
public:
virtual double area()const=0;
};
class Circle:public Shape
{
public:
Circle(double r):radius(r) {}
virtual double area()
const
{
return 3.14159*radius*radius;
}
protected:
double radius;
};
class Square:public Shape
{
public:
Square(double s):side(s) {}
virtual double area()
const
{
return side*side;
}
protected:
double side;
};
class Rectangle:public Shape
{
public:
Rectangle(double w,double h):width(w),height(h) {}
virtual double area()
const
{
return width*height;
}
protected:
double width,height;
};
class Trapezoid:public Shape
{
public:
Trapezoid(double t,double b,double h):top(t),bottom(b),height(h) {}
virtual double area()
const
{
return ((top+bottom)*height*0.5);
}
protected:
double top,bottom,height;
};

class Triangle:public Shape
{
public:
Triangle(double w,double h):width(w),height(h) {}
virtual double area()
const
{
return 0.5*width*height;
}
protected:
double width,height;
};

int main()
{
Circle circle(12.6);
Square square(3.5);
Rectangle rectangle(4.5,8.4);
Trapezoid trapezoid(2.0,4.5,3.2);
Triangle triangle(4.5,8.4);
Shape*pt[5]= {&circle,&square,&rectangle,&trapezoid,&triangle};
double areas=0.0;
for(int i=0; i<5; i++)
{
areas=areas+pt[i]->area();
}
cout<<"totol of all areas="<<areas<<endl;
return 0;
}
楼上错了一个字母bottom(t)应该改成bottom（b）。

Answer 3

完全不懂