Question

下面Shape类是一个表示形状的抽象类，Area （ ）为求图形面积的函数。请从Shape类派生梯形类（Trapezoid）

下面Shape类是一个表示形状的抽象类，Area （ ）为求图形面积的函数。请从Shape类派生梯形类（Trapezoid）、圆形类（Circle）,三角形类（Triangle），并给出具体的求面积函数。其中，所有派生类计算面积需要用到的参数由构造函数给出，梯形面积计算需要上底、下底和高，三角形面积需要底和高，圆形面积需要半径。
形状的抽象类声明如下：
class Shape {
public:
virtual double Area（ ） = 0;
};

Answer 1

看看这样写行不，我自己编的如有错误还请指正：

#include<iostream>
#define PI 3.142
using namespace std;
class Shape
{
protected:
double R;
double Triangle_S;
double Triangle_H;
double Trapezoid_ON;
double Trapezoid_DOWN;
double Trapezoid_H;
public:
virtual void area(){};

};
class Circle:public Shape
{
public:
Circle(double r)
void area()

};
class Triangle:public Shape
{
public:
Triangle(double s,double h)
void area()

};

class Trapezoid:public Shape
{
public:
Trapezoid(double ON,double DOWN,double H)
void area()

};
void main()
{
Circle a(2);//求圆面积
a.area();
Triangle b(2,2);//求三角形面积
b.area();
Trapezoid c(2,2,2);//求梯形面积
c.area();

}

Answer 2

class Trapezoid : public Shape
{
private:
double top;
double bottom;
double height;
public:
Trapezoid(double t, double b, double h)
{
top = t;
bottom = b;
height = h;
}

double Area()
{
return (top + bottom) * height / 2;
}
};

#define PI 3.1415926
class Circle : public Shape
{
private:
double r;
public:
Circle(double r)
{
this->r = r;
}

double Area()
{
return PI * r * r;
}
};

class Triangle : public Shape
{
private:
double bottom;
double height;
public:
Triangle(double b, double h)
{
bottom = b;
height = h;
}

double Area()
{
return bottom * height / 2;
}
};

Answer 3

已过了爱做梦的年纪
却还是喜欢在午后做那白日梦
徘徊在梦中那棵老槐树旁
知了叫着落寞了的清愁
往昔的疼痛还在心间
残缺了的记忆已经滑落