Question

C++试题：声明和实现一个时间类time24:a)实现获得和设置由时，分组成的24小时制时间的方法（具体看补充）

用C++声明和实现一个时间类time24:
a)实现获得和设置由时，分组成的24小时制时间的方法；
b)编写程序实现“+”运算，即实现time24对象与整型分钟数相加的运算，要求该运算返回一个time24对象；
c)实现time24类的等价运算符重载，即比较两个time24对象是否相等；
d)实现输入和输出重载。
要求该类具有构造函数，并适当使用友元函数和运算符重载方法。

Answer 1

#include <exception>
#include <ostream>

class invalid_time : std::exception {};

class time24
{
public:
time24(unsigned hour, unsigned min);
~time24();

void set(unsigned hour, unsigned min);
void add_min(unsigned min);

unsigned hour() const;
unsigned min() const;

private:
unsigned _hour;
unsigned _min;

friend bool operator==(time24 const&, time24 const&);
};

time24::time24(unsigned hour, unsigned min)
: _hour(0), _min(0)
{
set(hour, min);
}

time24::~time24()
{
}

void time24::set(unsigned hour, unsigned min)
{
if( hour>23 || min>59 )
throw invalid_time();

_hour = hour;
_min = min;
}

void time24::add_min(unsigned min)
{
unsigned dh = (_min + min) / 60;

_hour = (_hour + dh) % 24;
_min = (_min + min) % 60;
}

unsigned time24::hour() const
{
return _hour;
}

unsigned time24::min() const
{
return _min;
}

time24& operator+(time24& t, unsigned min)
{
t.add_min(min);
return t;
}

time24& operator+(unsigned min, time24& t)
{
return operator+(t, min);
}

bool operator==(time24 const& lhs, time24 const& rhs)
{
return lhs._hour == rhs._hour
&& lhs._min == rhs._min;
}

std::ostream& operator<<(std::ostream& os, time24 const& t)
{
os << "hour=" << t.hour() << ", min=" << t.min();
return os;
}

唉，这5分赚得累呀