写一个程序，定义抽象基类Shape,由它派生出5个派生类

写一个程序，定义抽象基类Shape,由它派生出5个派生类，Cirle（圆形）、Square（正方形）、Rectangle（矩形）、Trapezoid（梯形）、Triangle（三角形）。用虚函数分别计算几种图形面积，并求他们的和。要求用基类指针数组，使它的每个元素指向一个派生类对象。

 

#include<iostream>
using namespace std;
/*
    圆面积S=3.14*r*r
    矩形面积S=长*宽
    三角形面积S=(底*高)/2
    正方形面积S=a*a
    梯形面积S=(（上底+下底）*高)/2
*/
class Shape//抽象基类
{
public:
    virtual float area()const=0;
    virtual void display()const=0;
};
class Circle:public Shape// 园面积
{
public:
    Circle(double a):r(a){}
    virtual float area()const{return 3.14*r*r;}
    virtual void display()const
    {
        cout<<"圆面积"<<area()<<endl;
    }

private:
    double r;
};

class Rectangle:public Shape//矩形面积
{
public:
    Rectangle(double a,double b):l(a),w(b){}
    virtual float area()const{return l*w;}
        virtual void display()const
    {
        cout<<"矩形面积"<<area()<<endl;
    }
private:
    double l;
    double w;
};
class Triangle:public Shape//三角形面积
{
public:
    Triangle(double a,double b):d(a),h(b){}
    virtual float area()const{return (d*h)/2;}
        virtual void display()const
    {
        cout<<"三角形面积"<<area()<<endl;
    }
private:
    double d;
    double h;
};
class Square:public Shape//正方形面积
{
public:
    Square(double a):a1(a){}
    virtual float area()const{return a1*a1;}
        virtual void display()const
    {
        cout<<"正方形面积"<<area()<<endl;
    }
private:
    double a1;
};
class Trapezoid:public Shape//梯形面积
{
public:
    Trapezoid(double sd,double xd,double h):shad(sd),xiad(xd),hight(h){}
    virtual float area()const{return ((shad+xiad)*hight)/2;}
        virtual void display()const
    {
        cout<<"梯形面积"<<area()<<endl;
    }
private:
    double shad;
    double xiad;
    double hight;
};

int main()
{

    Circle c1(4);
    Rectangle r1(3,6);
    Triangle t1(2.5,5);
    Square s1(3.4);
    Trapezoid tr1(3.2,4.5,7);
    Shape *p[5]={&c1,&r1,&t1,&s1,&tr1};

    int i;
    double m=0.0;
    for (i=0;i<5;i++)
      {
          p[i]->display();
          m=m+p[i]->area();
    }


    cout<<"总面积:"<<m<<endl;

}