c++ - std::map 中的元素是否保证有序？

Question

这只是实现的副作用(红黑树)还是顺序由 c++ 标准保证？

Answer 1

有序迭代不是实现细节；它由 C++ 标准保证。它是所有关联容器的基本属性 (C++03 §23.1.2/9):

The fundamental property of iterators of associative containers is that they iterate through the containers in the non-descending order of keys where non-descending is defined by the comparison that was used to construct them. For any two dereferenceable iterators i and j such that distance from i to j is positive,

    value_comp(*j, *i) == false

value_comp是构建 map 的比较器(默认情况下，它是 std::less<T> )。