I know that the STL containers like set and map are sorted but how are they actually sorted? What is the underlying structure?
I couldn't find any books about it.
I'm a C++ beginner please don't judge me. :)
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5`std::map` is usually built on top of a [red-black tree](https://en.wikipedia.org/wiki/Red%E2%80%93black_tree). – r3mus n0x Nov 13 '18 at 12:41
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2@CoryKramer, the linked questions all presume that `std::map` is implemented using a red-black tree. The question "how is std::map implemented?" is a better fit. – Peter Ruderman Nov 13 '18 at 12:44
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So both are using the red-black tree? I heard something about the strict weak ordering criterion – Shalomi90 Nov 13 '18 at 12:45
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1I took it like the OP asking by how they are sorted ? The answer is by default they use the operator `<` less than. – darune Nov 13 '18 at 12:47
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1@r3musn0x Why are you answering in the comments section? – Lightness Races in Orbit Nov 13 '18 at 16:44
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@LightnessRacesinOrbit I thought the same :) – Shalomi90 Nov 13 '18 at 20:11
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For both std::map and std::set, it is implementation defined how the sorting is being done. The underlying data structure should sort the elements somehow:
Internally, the elements in a
mapare always sorted by its key following a specific strict weak ordering criterion indicated by its internal comparison object (of type Compare).
(same holds for set.)
A typical data structure for these containers is red black tree or a binary search tree.
gsamaras
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