类的多态性

分别定义抽象类Shape，由它派生出5个派生类Circle（圆形）、Square（正方形）、Rectangle（矩形）、Trapezoid（梯形）、Triangle（三角形）。
① 要求使用基类指针数组，使它的每一个元素指向一个派生类对象。
② 用虚函数分别计算这些图形的周长和面积，并分别求出它们的和。
③ 实现指定的功能，按要求撰写实验报告。

代码仅供参考

#include <iostream>
#include <string>
using namespace std;

const double PI=3.14;

class Shape
{
 public:
 virtual float perimeter() const {return 0.0;}//周长 
 virtual float area() const {return 0.0;}//面积 
 virtual void shapeName() const = 0;//虚函数 
};

class Circle:public Shape
{
 public:
 Circle(float r=0);
 virtual float perimeter() const;
 virtual float area() const;
 virtual void shapeName() const {cout << "圆:";}
 protected:
 float radius;
};
//声明Circle类成员函数
Circle::Circle(float r):radius(r){}
float Circle::perimeter() const {return PI*radius*2;}
float Circle::area() const {return PI*radius*radius;} 

class Square:public Shape
{
 public:
 Square(float a=0);
 virtual float perimeter() const;
 virtual float area() const;
 virtual void shapeName() const {cout << "正方形:";}
 protected:
 float sideLength;
};
//声明Square类成员函数
Square::Square(float a):sideLength(a){} 
float Square::perimeter() const {return 4*sideLength;}
float Square::area() const {return sideLength*sideLength;} 

class Rectangle:public Shape
{
 public:
 Rectangle(float a=0, float b=0);
 virtual float perimeter() const;
 virtual float area() const;
 virtual void shapeName() const {cout << "矩形:";}
 protected:
 float sideLength1;
 float sideLength2;
};
//声明Rectangle类成员函数
Rectangle::Rectangle(float a, float b):sideLength1(a),sideLength2(b){} 
float Rectangle::perimeter() const {return 2*sideLength1+2*sideLength2;}
float Rectangle::area() const {return sideLength1*sideLength2;} 

class Trapezoid:public Shape
{
 public:
 Trapezoid(float a=0, float b=0,float c=0,float d=0,float e=0);
 virtual float perimeter() const;
 virtual float area() const;
 virtual void shapeName() const {cout << "梯形:";}
 protected:
 float upper_bottom;
 float under_bottom;
 float height;
 float length1;
 float length2;
};
//声明Trapezoid类成员函数
Trapezoid::Trapezoid(float a, float b, float c, float d, float e):
           upper_bottom(a),under_bottom(b),height(c),length1(d),length2(e){} 
float Trapezoid::perimeter() const {return length1+length2+upper_bottom+under_bottom;}
float Trapezoid::area() const {return (upper_bottom+under_bottom)*height/2;} 

class Triangle:public Shape
{
 public:
 Triangle(float a=0, float b=0, float c=0, float d=0);
 virtual float perimeter() const;
 virtual float area() const;
 virtual void shapeName() const {cout << "三角形:";}
 protected:
 float bottom;
 float height;
 float sideLength1;
 float sideLength2;
};
//声明Triangle类成员函数
Triangle::Triangle(float a, float b, float c, float d):
                   bottom(a),height(b),sideLength1(c),sideLength2(d){} 
float Triangle::perimeter() const {return bottom*height/2;}
float Triangle::area() const {return sideLength1+sideLength2+bottom;} 

int main()
{
 Circle circle(3);
 Square square(4);
 Rectangle rectangle(3,4);
 Trapezoid trapezoid(2,10,3,5,5);
 Triangle triangle(6,4,5,5);
 Shape *pt[5]={&circle,&square,&rectangle,&trapezoid,&triangle};
 int i,j;
 for(i=0;i<5;i++)
 {
 pt[i]->shapeName();
 cout<<"perimeter="<<pt[i]->perimeter()<<",area="<<pt[i]->area()<<endl;
 }
 float sum1=0,sum2=0;
 for(i=0;i<5;i++)
 {
 sum1+=pt[i]->perimeter();
 sum2+=pt[i]->area();
 }
 cout << "总周长为：" << sum1 << endl;
 cout << "总面积为：" << sum2 << endl;
 return 0;
}