定义一个时间的类，其中成员数据包括小时、分、秒，成员函数为构造函数。要求增加适当的成员函数，重载＋、－、＋＝及输入输出流，来实现时间类对象的直接输入输出及两个时间的运算。-Define a time class member data which includes hours, minutes, seconds, member functions as a constructor. Request for additional appropriate member functions, overloaded+,-,+ =, and input and output streams to achieve operational direct input and output time of two class objects of time.