Question

编写程序，定义抽象基类Shape（形状），由他派生出三个派生类

编写程序，定义抽象基类Shape（形状），由他派生出三个派生类：Circle(圆形)、Rectangle（矩形）和Square（正方形），用函数函数ShowArea（）分别显示各种图形的面积，最后还有显示所有图形的总面积。要求用基类指针数组，使他的每一个元素指向一个派生类对象

Answer 1

不晓得你显示所有图形的总面积的函数放在哪里？

const double PI = 3.14;

class Shape
{
public:
virtual double ShowArea() = 0;
};

class Circle:public Shape
{
private:
double radius;
public:
Circle(double r):radius(r){}
double ShowArea(){return PI*radius*radius;}
};

class Rectangle:public Shape
{
private:
double length;
double width;
public:
Rectangle(double l, double w):length(l), width(w){}
double ShowArea(){return length*width;}
};

class Square:public Shape
{
private:
double length;
public:
Square(double l):length(l){}
double ShowArea(){return length*length;}
};

void main()
{
Circle circle(2);
Rectangle rect(3,4);
Square square(5);

Shape * arr[3] = {&circle, &rect, &square};

for(int i=0; i<3; i++)
{
cout << arr[i]->ShowArea() << endl;
}
}

Answer 2

书上应该有，你找找