c++ - std::map 的顺序

Question

对于 std::map ，我能永远相信吗begin()迭代时根据类型的比较运算符返回具有最小键的元素？

换句话说...

威尔std::map<Key, SomeClass>::iterator smallestKeyIt = someMap.begin();给我 map 中 key 最小的那对？

这是为 std::map 确定的顺序吗？或者我可以以某种方式配置它吗？我的理解是，在执行添加和删除元素等操作时，底层树结构保持有序。

Answer 1

can i always trust begin() to return the element with the smallest key according to comparison operators for the type?

是的。

Is this the ordering that is quaranteed for an std::map or can i configure it somehow?

是的。您可以通过指定比较器来配置比较的行为。 (默认的是 std::less。)

来自 cppreference :

template<
    class Key,
    class T,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<std::pair<const Key, T> >
> class map;

std::map is a sorted associative container that contains key-value pairs with unique keys. Keys are sorted by using the comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Maps are usually implemented as red-black trees.