I'm not the parent post, but many, many of the interviews I've done, the candidate just says "I'd use a hashtable." Why? well, the honest answer was because the candidate had another interview, and the answer was a hashtable. Now he knows hashtables. Okay great, but I'm not interested in whether or not you know how to use a hash table. I'm asking if you know how to choose which data structures fit the question, ie, can you program. I expect its the same reason google asks (used to?) everyone about red/black and b trees. Same thing, just levelled up a level.
What's horrifying is there are now people (occasionally) on /r/learnprogramming where the person can wax on for ages about obscure data structures or algorithms, but you ask them something simple (What sorta unit tests would I write for this? What should I keep in mind before deploying this app?) and it falls apart, they don't know how to program, they've just been reading crack-the-interview type books. (though at least that shows a _lot_ of gumption, dedicate, intelligence)
What's horrifying is there are now people (occasionally) on /r/learnprogramming where the person can wax on for ages about obscure data structures or algorithms, but you ask them something simple (What sorta unit tests would I write for this? What should I keep in mind before deploying this app?) and it falls apart, they don't know how to program, they've just been reading crack-the-interview type books. (though at least that shows a _lot_ of gumption, dedicate, intelligence)