#include <iostream>
using namespace std;

class DayOfYear
{
public:
    friend bool equal(DayOfYear date1,DayOfYear date2);    //友元
    DayOfYear(int the_month,int the_day);
    DayOfYear();
    void input();
    void output();
    int get_month();
    int get_day();
//private:
    void check_date();
    int month;
    int day;
};

int main ()
{
    DayOfYear today,bach_birthday(3,21);

    cout<<"输入今天日期：";
    today.input();
    cout<<"今天是";
    today.output();

    cout<<"xxx的生日是";
    bach_birthday.output();

    if(equal(today,bach_birthday))
        cout<<"happy!";
    else
        cout<<"unhappy!";

    return 0;
}

bool equal(DayOfYear date1,DayOfYear date2)
{
    return(date1.month == date2.month && date1.day ==date2.day);
}
DayOfYear::DayOfYear(int the_month,int the_day):month(the_month),day(the_day)
{
    //无动作
}

int DayOfYear::get_month()
{
    return month;
}
int DayOfYear::get_day()
{
    return day;
}
//使用iostream
void DayOfYear::input()
{
    cout<<"输入月份：";
    cin>>month;
    cout<<"输入日期:";
    cin>>day;
}
void DayOfYear::output()
{
    cout<<"月:"<<month<<",日:"<<day<<endl;
}

少个无参构造方法
DayOfYear(){}

#include <iostream>
using namespace std;

class DayOfYear
{
public:
    bool equal(DayOfYear date1,DayOfYear date2);    //友元
    DayOfYear(int the_month,int the_day);
    DayOfYear(){};
    void input();
    void output();
    int get_month();
    int get_day();

private:
    int month;
    int day;
};
bool DayOfYear:: equal(DayOfYear date1,DayOfYear date2)
{
    if(date1.month=date2.month&&date1.day==date2.day)
    return true;
    else return false;
   
}
DayOfYear::DayOfYear(int the_month,int the_day):month(the_month),day(the_day)
{
    //无动作
}

int DayOfYear::get_month()
{
    return month;
}
int DayOfYear::get_day()
{
    return day;
}
//使用iostream
void DayOfYear::input()
{
    cout<<"输入月份：";
    cin>>month;
    cout<<"输入日期:";
    cin>>day;
}
void DayOfYear::output()
{
    cout<<"月:"<<month<<",日:"<<day<<endl;
}

int main ()
{
    DayOfYear today,bach_birthday(3,21),date1;

    cout<<"输入今天日期：";
    today.input();
    cout<<"今天是";
    today.output();

    cout<<"xxx的生日是";
    bach_birthday.output();

    if(date1.equal(today,bach_birthday))
        cout<<"happy!";
    else
        cout<<"unhappy!";

    return 0;
}

还有格式不是很好，看的不舒服啊，

果断不会

要淡定