定义一个Point类，派生出Rectangle类和Circle类，计算各派生类对象的面积Area()C++

下面是一个简单的实现：

#include <iostream>
using namespace std;

class Point {
protected:
    int x, y;
public:
    Point(int x = 0, int y = 0) : x(x), y(y) {}
};

class Rectangle : public Point {
private:
    int width, height;
public:
    Rectangle(int x = 0, int y = 0, int width = 0, int height = 0) : Point(x, y), width(width), height(height) {}
    int Area() { return width * height; }
};

class Circle : public Point {
private:
    int radius;
public:
    Circle(int x = 0, int y = 0, int radius = 0) : Point(x, y), radius(radius) {}
    double Area() { return 3.14 * radius * radius; }
};

int main() {
    Rectangle rect(1, 2, 3, 4);
    Circle circle(5, 6, 7);

    cout << "Rectangle area: " << rect.Area() << endl;
    cout << "Circle area: " << circle.Area() << endl;

    return 0;
}

Point 类作为基类，Rectangle 和 Circle 类分别继承 Point 类。Rectangle 和 Circle 类都有一个 Area 函数，分别计算矩形和圆的面积。在 main 函数中创建一个 Rectangle 对象和一个 Circle 对象，并分别调用它们的 Area 函数输出结果。