定义点类 Point，重载运算符“＋”、“－”、“＝＝”、“！=”、“++”、“--”、“>>”、“<<”，实现两个点的相加、相减、相等、不等、自增、自减、输入和输出运算。

下面是 Point 类的实现代码：

#include <iostream>
using namespace std;

class Point {
private:
    int x, y;
public:
    Point(int x = 0, int y = 0) {
        this->x = x;
        this->y = y;
    }

    Point operator+(const Point& p) {
        return Point(x + p.x, y + p.y);
    }

    Point operator-(const Point& p) {
        return Point(x - p.x, y - p.y);
    }

    bool operator==(const Point& p) {
        return x == p.x && y == p.y;
    }

    bool operator!=(const Point& p) {
        return !(*this == p);
    }

    Point operator++() {
        x++;
        y++;
        return *this;
    }

    Point operator++(int) {
        Point p(*this);
        ++(*this);
        return p;
    }

    Point operator--() {
        x--;
        y--;
        return *this;
    }

    Point operator--(int) {
        Point p(*this);
        --(*this);
        return p;
    }

    friend istream& operator>>(istream& is, Point& p) {
        is >> p.x >> p.y;
        return is;
    }

    friend ostream& operator<<(ostream& os, const Point& p) {
        os << "(" << p.x << ", " << p.y << ")";
        return os;
    }
};

我们可以通过以下方式来测试 Point 类的功能：

int main() {
    Point p1(1, 2), p2(3, 4);
    cout << "p1 = " << p1 << endl;
    cout << "p2 = " << p2 << endl;

    Point p3 = p1 + p2;
    cout << "p1 + p2 = " << p3 << endl;

    Point p4 = p2 - p1;
    cout << "p2 - p1 = " << p4 << endl;

    cout << "p1 == p2: " << (p1 == p2) << endl;
    cout << "p1 != p2: " << (p1 != p2) << endl;

    cout << "++p1 = " << ++p1 << endl;
    cout << "p1++ = " << p1++ << endl;
    cout << "p1 = " << p1 << endl;

    cout << "--p2 = " << --p2 << endl;
    cout << "p2-- = " << p2-- << endl;
    cout << "p2 = " << p2 << endl;

    Point p5;
    cout << "Enter a point: ";
    cin >> p5;
    cout << "You entered " << p5 << endl;

    return 0;
}

输出结果为：

p1 = (1, 2)
p2 = (3, 4)
p1 + p2 = (4, 6)
p2 - p1 = (2, 2)
p1 == p2: 0
p1 != p2: 1
++p1 = (2, 3)
p1++ = (2, 3)
p1 = (3, 4)
--p2 = (2, 3)
p2-- = (2, 3)
p2 = (1, 2)
Enter a point: 5 6
You entered (5, 6)