Question

用C/C++定义一个点类Point/

1.用构造函数初始化类Point的对象?
2.定义函数Distance,计算平面上两点间的距离?
请高手们指点一下.我会好感谢高手们的.

Answer 1

/***************************************************************\
* Copyright (c) 2009 eryar All rights reserved. *
* *
* File : Main.CPP *
* Date : 2009-01-19 19:00 *
* Author : eryar@163.com *
* *
* Description: *
* 编写一个程序，设计一个点类Point，求两个点之间的距离。 *
\***************************************************************/

#include <cmath>
#include <iostream>
using namespace std;

class Point{
public:
Point(double _x = 0, double _y = 0) : x(_x), y(_y) { cout<<"[class Point default constructor]"<<endl; }
void ShowPoint() const { cout<<"x = "<<x<<endl<<"y = "<<y<<endl; }
void SetPoint(float X, float Y) { x = X; y = Y; }
~Point() { cout<<"[class Point default destructor ]"<<endl; }
protected:
//friend float Distance(const Point &, const Point &);
private:
friend float Distance(const Point &, const Point &);
float x;
float y;
}; // End of Point class

float Distance(const Point &p1, const Point &p2)
{
float distance = 0;
float DeltaX = 0;
float DeltaY = 0;

DeltaX = p2.x - p1.x;
DeltaY = p2.y - p1.y;

DeltaX *= DeltaX;
DeltaY *= DeltaY;

distance = sqrt(DeltaX + DeltaY);

return distance;
}

int main(int argc, char *argv[])
{
Point PointOne, PointTwo;

PointOne.SetPoint(6, 8);

PointOne.ShowPoint();
PointTwo.ShowPoint();

cout<<"The distance between two point is : "
<<Distance(PointOne, PointTwo)<<endl;

return 0;
}

/*
笔记:
1. 友元函数可以访问类中的的私有数据成员, 与在类中声明的位置无关;
2. 当函数参数为类时，应尽量设置为引用类型, 这样可以提高性能;
3. 当对象本体和实体一致时，可以使用默认的拷贝构造函数;
*/

Answer 2

#include <math.h> //开方函数sqrt和平方函数pow在此
#include <iostream>
using namespace std;

class Point
{
public:
Point(double x,double y) //构造函数初始化Px,Py
{
Px = x; Py = y;
}
friend double Distance(Point p1,Point p2); //友元函数可以访问类的私有成员
private:
double Px,Py;
};

double Distance(Point p1,Point p2) //求距离函数
{
double result;
result = sqrt( pow(p1.Px-p2.Px,2) + pow(p1.Py-p2.Py,2) );//距离公式
return result;
}

void main()
{
Point p1(1,2), p2(1.5,2);
cout<<"p1与p2的距离是："<<Distance(p1,p2)<<endl;
}

Answer 3

一楼已经提供了完整的代码了。