8.5 (C++)

The Point2D class was created to model a point in a two-dimensional space.
The Point2D class has the properties x and y that represent the x and the y coordinates, two getter functions for x and y, and the function for returning the distance between two points.
Create a class named Point3D to model a point in a three-dimensional space. Let Point3D be derived from Point2D with the following additional features:
A data field named z that represents the z-coordinate.
A no-arg constructor that constructs a point with coordinate (0,0,0).
A constructor that constructs a point with three specified coordinates.
A getter function that returns the value for the z coordinate.
Override the distance function to return the distance between two points in the tree dimensional space.
Hint:
In order to override a function in a base class, a derived class should define a function with exactly the same signature. A signature of a function includes the function name and the list of its parameter types.
A reference, which has been down-casted to a parent type, can be up-casted to the children class using c-casting or dynamic-casting.
EXAMPLE INPUT:
1 2 3
10 20 30
EXAMPLE OUTPUT:
point1.getX() = 1
point1.getY() = 2
point1.getZ() = 3
point2.getX() = 10
point2.getY() = 20
point2.getZ() = 30
point1.distance(point2) = 33.6749
主程序 (不能修改)

#include <cmath>

class Point2D
{
private:
    double x;
    double y;
    
public:
    Point2D() {
        x = 0;
        y = 0;
    }
    
    double getX() {
        return x;
    }
    
    double getY() {
        return y;
    }
    
    void setX(double x) {
        this->x = x;
    }
    
    void setY(double y) {
        this->y = y;
    }
    
    virtual double distance(Point2D & point2) {
        double dx = x - point2.x;
        double dy = y - point2.y;
        return sqrt(dx * dx + dy * dy);
    }
    
};

#include "source.cpp"

#include <iostream>
using namespace std;

void printDistance(Point2D & point1, Point2D & point2) {
    cout << "point1.distance(point2) = " << 
        point1.distance(point2) << endl;
}

int main() {
    double x1;
    double y1;
    double z1;
    double x2;
    double y2;
    double z2;
    cin >> x1;
    cin >> y1;
    cin >> z1;
    cin >> x2;
    cin >> y2;
    cin >> z2;
    
    Point3D point1(x1, y1, z1);
    Point3D point2(x2, y2, z2);
    
    cout << "point1.getX() = " << point1.getX() << endl;
    cout << "point1.getY() = " << point1.getY() << endl;
    cout << "point1.getZ() = " << point1.getZ() << endl;
    cout << "point2.getX() = " << point2.getX() << endl;
    cout << "point2.getY() = " << point2.getY() << endl;
    cout << "point2.getZ() = " << point2.getZ() << endl;
    
    printDistance(point1, point2);
}

我的答案

class Point3D :public Point2D
{
private:
    double x;
    double y;
    double z;
public:
    Point3D() {
        x = 0;
        y = 0;
        z = 0;
    }
    
    Point3D(double x1,double y1,double z1) {
        x = x1;
        y = y1;
        z = z1;
    }
    
    double getX() {
        return x;
    }
    
    double getY() {
        return y;
    }
    
    void setX(double x) {
        this->x = x;
    }
    
    void setY(double y) {
        this->y = y;
    }
    
    double getZ() {
        return z;
    }
    
    void setZ(double z) {
        this->z = z;
    }
    
   virtual double distance(Point2D & point2) {
      Point3D point3=dynamic_cast<Point3D &>(point2);
        double dx = this->x - point3.getX();
        double dy = this->y - point3.getY();
        double dz = this->z - point3.getZ();
        return sqrt(dx * dx + dy * dy + dz * dz);
    }
    
};