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Is this just an implementation side effect (red-black tree) or the order is guaranteed by the c++ standard?
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are STL maps ordered? Yes, a std::map<K,V> is ordered based on the key, K , using std::less<K> to compare objects, by default.
By default, a Map in C++ is sorted in increasing order based on its key.
Yes, std::map is a sorted container, ordered by the Key with the supplied Comparator . So it is guaranteed.
A Map store the elements in the sorted order of keys. For example, we have a map of words and its frequency count as key – value pair i.e. Map internally stores the above elements in sorted order of keys i.e. Therefore, iterating over a map will give pair elements in above order.
Ordered iteration is not an implementation detail; it is guaranteed by the C++ standard. It is a fundamental property of all associative containers (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
iandjsuch that distance fromitojis positive,value_comp(*j, *i) == false
value_comp is the comparator with which the map was constructed (by default, it is std::less<T>).
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