4.23打卡

class Person
{
    public:
    virtual void bellRing() {}
    virtual ~Person(){}
};

class Student:public Person {
    public:
    void bellRing(){
        cout << "I am a student learning in classroom." <<  endl;
    }
    
    ~Student (){
    cout <<"A student object destroyed." << endl;
    }
};


class Teacher:public Person {
    public:
    void bellRing(){
        cout << "I am a teacher teaching in classroom." <<  endl;
    }
    
    ~Teacher (){
    cout <<"A teacher object destroyed." << endl;
    }
};

class Principal:public Person {
    public:
    void bellRing(){
        cout << "I am the principal inspecting in campus." <<  endl;
    }
    
    ~Principal (){
    cout <<"A principal object destroyed." << endl;
    }
};

 

 

#include<bits/stdc++.h>
using namespace std;
#define PI 3.14159
class Shape
{
protected:
    double a, b, c;
public:
    Shape(double a=0,double b=0,double c=0)
    {
        this->a = a; this->b = b;
        this->c = c;
    }
    virtual double getmianji() = 0;
};
class Circle:public Shape//（圆形）
{
public:
    Circle(double a) :Shape(a) {}
    double getmianji()
    {
        return PI * a * a;
    }
};
class Square :public Shape//（正方形）
{
public:
    Square(double a) :Shape(a) {}
    double getmianji()
    {
        return  a * a;
    }
};
class Rectangle :public Shape//（长方形）
{
public:
    Rectangle(double a,double b) :Shape(a,b) {}
    double getmianji()
    {
        return a*b;
    }
};
class Trapezoid :public Shape//（梯形）
{
public:
    Trapezoid(double a,double b,double c) :Shape(a,b,c) {}
    double getmianji()
    {
        return (a + b) * c * 0.5;
    }
};
class Triangle :public Shape//（三角形）
{
public:
    Triangle(double a,double b) :Shape(a,b) {}
    double getmianji()
    {
        return a*b*0.5;
    }
};
int main()
{
    double a, b, c;
    cin >> a;
    Circle C(a);
    cin >> a ;
    Square s(a);
    cin >> a >> b;
    Rectangle r(a, b);
    cin >> a >> b >> c;
    Trapezoid t1(a, b, c);
    cin >> a >> b;
    Triangle t2(a, b);
    Shape* sp[5] = { &C,&s,&r,&t1,&t2 };
    double totalareas = 0;
    for (int i = 0; i < 5; i++)
    {
        totalareas += sp[i]->getmianji();
    }
    printf("total of all areas = %0.3f", totalareas);
    system("pause");
}