sdut oj3-7 类的友元函数的应用

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3-7 类的友元函数的应用
Time Limit: 1000MS Memory Limit: 65536KB
Problem Description
通过本题目的练习可以掌握类的友元函数的定义和用法
要求设计一个点类Point，它具有两个double型的数据成员x，y。为该类设计构造函数。并为其添加一个友元函数用于计算并输出两点间的距离；再添加一个输出成员函数用于输出点的信息。

并编写主函数，实现以下的输入输出内容。
Input

4个double型的数，中间用一个空格间隔。
Output

输出数据共3行，前两行用于显示要求距离的两个点的信息，第三行显示两点的距离。
Example Input

5 6 2 3

Example Output

The first point is the coordinate:X=5,Y=6
The second point is the coordinate:X=2,Y=3
The distance between the two points is:4.24264

Hint

Author
黄晶晶

代码实现：

#include <iostream>#include <math.h>#include <iomanip>using namespace std;class Point{private:    double x,y;public:    Point(double a = 0,double b = 0);    void display()    {        cout<<"X="<<x<<","<<"Y="<<y<<endl;//    }    friend double dist(Point &A,Point &B);};Point::Point(double a,double b){    x = a;y = b;}double dist(Point &A,Point &B){    double a = (A.x - B.x)*(A.x - B.x) + (A.y - B.y)*(A.y - B.y);    return sqrt(a);}int main(){    double a,b,c,d;    cin>>a>>b>>c>>d;    Point A(a,b);    cout<<"The first point is the coordinate:";    A.display();    Point B(c,d);    cout<<"The second point is the coordinate:";    B.display();    cout<<"The distance between the two points is:"<<dist(A,B)<<endl;    return 0;}

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