BFS queues are not particularly difficult to describe, and deciding whether or not to do breadth or depth first is something I think about all the time.  Frequently, for instance, in data access patterns, that decision can have a very big effect on performance.  I can&#x27;t agree that it&#x27;s a random trivia question.<p>Edit: Ok, let me add some nuance here.  I think we both probably agree that implementing a shortest path algo perfectly in an interview setting is beyond reasonable or useful.  But I would expect an engineer to be able to have a discussion about it that shows me they understand the basic concepts and given google and a bit of time could relearn that.  But without the complexity of shortest path I would not expect basic BFS to be outside of the scope of an interview.  I guess that&#x27;s just where I draw my lines.