一、重载加号

#include <iostream>
using namespace std;
class Person{
    friend ostream& operator<<(ostream& cout, Person& p);
public:
    Person(){
    }
    Person(int score){
        this->m_Score = score;
    }
//    Person operator+(const Person& p){  //成员函数的方式 
//        Person temp;
//        temp.m_Score = this->m_Score + p.m_Score;
//        return temp; 
//    }
    int m_Score;
};
ostream& operator<<(ostream& cout, Person& p){
    cout << "score = " << p.m_Score << endl;
    return cout;
}
Person operator+(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score + per2.m_Score;
    return temp;
}
int main(){
    Person per1(10);
    Person per2(20);
    Person per3 = per1 + per2;
    cout << per3 << endl;
    return 0;
}

二、重载减号

#include <iostream>
using namespace std;
class Person{
    friend ostream& operator<<(ostream& cout, Person& p);
public:
    Person(){
    }
    Person(int score){
        this->m_Score = score;
    }
//    Person operator+(const Person& p){  //成员函数方式重载加号
//        Person temp;
//        temp.m_Score = this->m_Score + p.m_Score;
//        return temp; 
//    }
//    Person operator-(const Person& p){  //成员函数方式重载减号
//        Person temp;
//        temp.m_Score = this->m_Score - p.m_Score;
//        return temp;
//    }
    int m_Score;
};
ostream& operator<<(ostream& cout, Person& p){
    cout << "score = " << p.m_Score << endl;
    return cout;
}
Person operator+(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score + per2.m_Score;
    return temp;
}
Person operator-(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score - per2.m_Score;
    return temp;
}
int main(){
    Person per1(10);
    Person per2(20);
    Person per3 = per1 + per2;
    Person per4 = per3 - per2;
    cout << "per3 : " << per3 << endl;
    cout << "per4 : " << per4 << endl;
    return 0;
}

三、重载乘号

#include <iostream>
using namespace std;
class Person{
    friend ostream& operator<<(ostream& cout, Person& p);
public:
    Person(){
    }
    Person(int score){
        this->m_Score = score;
    }
//    Person operator+(const Person& p){  //成员函数的方式 
//        Person temp;
//        temp.m_Score = this->m_Score + p.m_Score;
//        return temp; 
//    }
//    Person operator-(const Person& p){
//        Person temp;
//        temp.m_Score = this->m_Score - p.m_Score;
//        return temp;
//    }
//    Person operator*(const Person& p){
//        Person temp;
//        temp.m_Score = this->m_Score * p.m_Score;
//        return temp;
//    }
    int m_Score;
};
ostream& operator<<(ostream& cout, Person& p){
    cout << "score = " << p.m_Score << endl;
    return cout;
}
Person operator+(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score + per2.m_Score;
    return temp;
}
Person operator-(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score - per2.m_Score;
    return temp;
}
Person operator*(const Person& per1,const Person& per2){  // 全局函数的方式 
    Person temp;
    temp.m_Score = per1.m_Score * per2.m_Score;
    return temp;
}
int main(){
    Person per1(10);
    Person per2(20);
    Person per3 = per1 + per2;
    Person per4 = per3 - per2;
    Person per5 = per1 * per2;
    cout << "per3 : " << per3 << endl;
    cout << "per4 : " << per4 << endl;
    cout << "per5 : " << per5 << endl;
    return 0;
}