[英]C++: std::map sorting
I am a newbie to C++, and this question may seem obvious to a lot of people. 我是C ++的新手,这个问题对于很多人来说似乎都很明显。
If I write something like 如果我写这样的话
std::map<int, double> m;
For example, 例如,
class own_int_less : public binary_function<int, int, bool>
{
public:
bool operator()( const double &left, const double &right ) const
{
return (abs(left - right) > epsilon) && (left < right);
};
double epsilon;
};
Thanks. 谢谢。
Is m guaranteed to be sorted according to int order?
是否保证m根据int顺序排序?
Yes. 是。 The default comparator is
std::less<Key>
, which in your case is std::less<int>
, which just uses <
as expected. 默认比较器为
std::less<Key>
,在您的情况下为std::less<int>
,它按预期使用<
Is it necessary to define a comparitor class to enforce the sorting?
是否有必要定义一个比较器类来执行排序?
No, because the previous answer was "yes"! 否,因为先前的答案是“是”!
When is the sorting actually occurred?
排序何时真正发生?
A typical map
implementation uses the comparator to insert a new element into the correct location. 典型的
map
实现使用比较器将新元素插入正确的位置。 The comparator is also used when doing a lookup. 查找时还使用比较器。
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