In current C++ STL, where are red-black tree used? (I assume map and set do?) Is the red-black tree used 2-3 tree (ie only left or right child can be red) or 2-3-4 tree (ie both left and right child can be red)? is there a red-black tree lib in STL?
std::map, std::multimap, std::set and std::multiset are often implemented in terms of red-black trees but doing so is not mandated by the standard. Since using a red-black tree is not required there is also no requirement for any particular flavor of RB tree.
I believe (though am not certain) that SGI's STL (upon which much of the original standard library is based) actually does have a red-black tree available. If it helps, I know boost::intrusive does have a reusable red-black tree implementation.