自增（二）

; class Time { public: Time(int m=0,int s=0):min(m),sec(s){} Time operator++() { if (++sec>=60) { sec%=60; min++; } return *this; } Time operator++(int) { if (++sec>=60) { sec%=60; min++; } return *this; } friend ostream& operator<<(ostream &,Time); private: int min; int sec; }; ostream& operator<<(ostream &output,Time t) { output<<t.min<<':'<<t.sec<<endl; return output; } int main() { Time t; t++; cout<<t; ++t; cout<<t; return 0; }