1.设有下面关于点Point类的定义，请在此基础上派生出一个矩形Rectangle类，用以描述矩形的左上角的顶点，并能够计算矩形的面积，并给出测试程序，测试程序里，定义矩形的对象，求出矩形的面积和矩形的位置（即左上顶点和右下顶点的坐标）。 class Point {public: Point(int a,int b){ x=a; y=b;} Point(){x=0;y=0;} int GetY(){return y;} int GetX(){return x;} void SetY(int b){ y=b;} void SetX(int a){ x=a;} private: int x; int y; };

派生出的Rectangle类的定义如下：

class Rectangle: public Point {
public:
  Rectangle(int a, int b, int w, int h): Point(a,b) {
    width = w;
    height = h;
  }
  int GetWidth() { return width; }
  int GetHeight() { return height; }
  void SetWidth(int w) { width = w; }
  void SetHeight(int h) { height = h; }
  int GetArea() { return width * height; }
  Point GetTopLeft() { return Point(GetX(), GetY()); }
  Point GetBottomRight() { return Point(GetX() + width, GetY() + height); }
private:
  int width;
  int height;
};

测试程序如下：

#include <iostream>
using namespace std;

int main() {
  Rectangle rect(0, 0, 5, 4);
  cout << "Area = " << rect.GetArea() << endl;
  cout << "Top-left point = (" << rect.GetX() << "," << rect.GetY() << ")" << endl;
  cout << "Bottom-right point = (" << rect.GetBottomRight().GetX() << "," << rect.GetBottomRight().GetY() << ")" << endl;
  return 0;
}

输出结果如下：

Area = 20
Top-left point = (0,0)
Bottom-right point = (5,4)

可以看到，矩形的面积是20，左上顶点的坐标为(0,0)，右下顶点的坐标为(5,4)。