Is there any principle to choose one over another between hash_map and map in STL?
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Is there any principle to choose one over another between hash_map and map in STL?
hash_mapis useful if you are only looking elements by their key. A possible use-case for ahash_mapwould be a dictionary. If the elements need to be in ordermapis the container for that.And just for clarification (because of the usage of the word “STL”):
hash_mapisn’t yet part of the C++ Standard Library, but it has been implemented in several C++ compilers.unordered_mapwas proposed in the C++ Technical Report 1, and it will be defined in the next edition of the standard, C++0x.