自加运算符的前置与后置的重载

#include <iostream>
using namespace std;
class Time
{public:
   Time(){minute=0;sec=0;}
   Time(int m,int s):minute(m),sec(s){}
   Time operator++();
   Time operator++(int);
   void display(){cout<<minute<<":"<<sec<<endl;}
  private:
   int minute;
   int sec;
 };
 

Time Time::operator++()
{if(++sec>=60)
  {sec-=60;
   ++minute;}
 return *this;
}
Time Time::operator++(int)
{Time temp(*this);
 sec++;
 if(sec>=60)
  {sec-=60;
   ++minute;}
 return temp;
}

  
int main()
{Time time1(34,59),time2;
 cout<<" time1 : ";
 time1.display();
 ++time1;
 cout<<"++time1: ";
 time1.display();
 time2=time1++;
 cout<<"time1++: ";
 time1.display();
 cout<<" time2 : ";
 time2.display();
 return 0;
}