定义一个表示点的类Point，类中有两个私有成员变量x和y；使用成员函数和友元函数两种方法，为该类重载以下运算符：加+ 增量++（包括前增和后增） ＝＝ 主函数中分别使用以上运算符。

使用成员函数重载运算符：

#include<iostream>
using namespace std;

class Point{
private:
    int x, y;
public:
    Point(int x=0, int y=0):x(x), y(y){}
    Point operator+(const Point& p){
        return Point(x+p.x, y+p.y);
    }
    Point& operator++(){ //前增量
        x++;
        y++;
        return *this;
    }
    Point operator++(int){ //后增量
        Point old = *this;
        x++;
        y++;
        return old;
    }
    bool operator==(const Point& p){
        return x==p.x && y==p.y;
    }
    friend ostream& operator<<(ostream& os, const Point& p){
        os<<"("<<p.x<<", "<<p.y<<")";
        return os;
    }
};

int main(){
    Point p1(1, 2), p2(3, 4), p3;
    p3 = p1 + p2;
    cout<<p1<<" + "<<p2<<" = "<<p3<<endl;
    if (p1 == p2){
        cout<<p1<<" == "<<p2<<endl;
    }else{
        cout<<p1<<" != "<<p2<<endl;
    }
    ++p1;
    cout<<"++"<<p1<<" = "<<p1<<endl;
    p2++;
    cout<<p2<<"++ = "<<p2<<endl;
    return 0;
}

使用友元函数重载运算符：

#include<iostream>
using namespace std;

class Point{
private:
    int x, y;
public:
    Point(int x=0, int y=0):x(x), y(y){}
    friend Point operator+(const Point& p1, const Point& p2){
        return Point(p1.x+p2.x, p1.y+p2.y);
    }
    Point& operator++(){ //前增量
        x++;
        y++;
        return *this;
    }
    Point operator++(int){ //后增量
        Point old = *this;
        x++;
        y++;
        return old;
    }
    friend bool operator==(const Point& p1, const Point& p2){
        return p1.x==p2.x && p1.y==p2.y;
    }
    friend ostream& operator<<(ostream& os, const Point& p){
        os<<"("<<p.x<<", "<<p.y<<")";
        return os;
    }
};

int main(){
    Point p1(1, 2), p2(3, 4), p3;
    p3 = p1 + p2;
    cout<<p1<<" + "<<p2<<" = "<<p3<<endl;
    if (p1 == p2){
        cout<<p1<<" == "<<p2<<endl;
    }else{
        cout<<p1<<" != "<<p2<<endl;
    }
    ++p1;
    cout<<"++"<<p1<<" = "<<p1<<endl;
    p2++;
    cout<<p2<<"++ = "<<p2<<endl;
    return 0;
}