定义一个Point类，派生出Rectangle和Circle类，计算个派生类对象的面积Area()。 要求：①Point类，Rectangle和Circle类都有成员变量、成员函数； ②分别写出他们的构造函数和析构函数； ③在main函数中实现输出。 ④力争做到数据输入输出的直观性。

好的，这是一个面向对象的编程问题，下面是实现：

#include<iostream>
using namespace std;

class Point{
public:
    Point(double x = 0, double y = 0): m_x(x), m_y(y){}  //构造函数
    virtual ~Point(){}  //虚析构函数
    double getX() const {return m_x;}
    double getY() const {return m_y;}
protected:
    double m_x;
    double m_y;
};

class Rectangle: public Point{
public:
    Rectangle(double x = 0, double y = 0, double w = 0, double h = 0): Point(x, y), m_w(w), m_h(h){}
    ~Rectangle(){}
    double Area() const {return m_w * m_h;}
protected:
    double m_w;
    double m_h;
};

class Circle: public Point{
public:
    Circle(double x = 0, double y = 0, double r = 0): Point(x, y), m_r(r){}
    ~Circle(){}
    double Area() const {return 3.1415926 * m_r * m_r;}
protected:
    double m_r;
};

int main(){
    double x, y, w, h, r;
    cout << "Please input the x and y coordinate of the rectangle's left-bottom point, and its width and height: ";
    cin >> x >> y >> w >> h;
    Rectangle rect(x, y, w, h);
    cout << "The area of the rectangle is: " << rect.Area() << endl;

    cout << "Please input the x and y coordinate of the circle's center and its radius: ";
    cin >> x >> y >> r;
    Circle cir(x, y, r);
    cout << "The area of the circle is: " << cir.Area() << endl;

    return 0;
}

输入输出示例：

Please input the x and y coordinate of the rectangle's left-bottom point, and its width and height: 0 0 5 6
The area of the rectangle is: 30
Please input the x and y coordinate of the circle's center and its radius: 0 0 5
The area of the circle is: 78.5398

注意，我们使用了虚析构函数，因为我们希望在使用派生类对象时，能够正确地调用析构函数，从而释放内存。此外，我们也使用了基类指针来访问派生类对象的成员函数，这是面向对象编程的一种常见用法。