I'm a big fan of trie-based interview questions because if an individual can call them out immediately, they know their data structures -- awesome. If they onl

I'm a big fan of trie-based interview questions because if an individual can call them out immediately, they know their data structures -- awesome. If they only know simple data structures, going from a hash to a hash of hashes is one of those "eureka" moments that can really shows how a candidate is willing to collaborate on a problem and react to new ideas. Heaps are an interesting data structure to use for interviewing, but I do find they can be a little less intuitive, and their use cases translate less directly to business logic and are more of an optimization task. It depends on what talents you're looking for on your team!