title: Efficiency of iterators in unordered_map (C++)
body: <p>I can't seem to find any information on this, so I turn to stackoverflow.  How efficient are the iterators of std::tr1::unordered_map in C++?  Especially compared to, say, list iterators.  Would it make sense to make a wrapper class that also holds all the keys in a list to allow for efficient iteration (my code does use a lot of iteration over the keys in an unordered_map).  For those who will recommend boost, I can't use it (for whatever reasons).</p>