[dangoldin]

I'm being defensive now but I think that's a pretty extreme view. Every answer is part of the interview process and it's not about the final destination. The more answers that people have the bigger the conversation and the more I can understand how someone thinks which is what you want to get out of an interview.

The fact that someone does quickly grasp the concept is a plus - why do you think it's the wrong approach? I definitely adapt my approach as I do more interviews so any feedback helps.

[Xk]

First of all, let me say this is a significantly better question than many I've seen. However, It disturbs me when someone is interviewing me and they are looking for a particular answer and they consider everything else wrong. Even when I find more efficient answers, if it's not theirs, it's wrong.

Think about it like those little kid riddles: "A man is found dead with a noose around his neck and a puddle of water at his feet. How is it he was killed?" Put on a stool and the stool was removed? Then add the restriction "There are no stools." He was lifted with the rope? "The rope was tied to a bar on the ceiling and couldn't be raised higher." Raised in the air by some strong people and then let hang? "No one raised him from the air." You can make guesses all day long and I can make up excuses about why you're wrong until you finally guess what I wanted you to guess -- that he was standing on a block of ice.

More specific to your question: when I read it the first thing that came to mind was just to have an array of booleans and for each word in the table set H(word) to true and then when looking up a word check if H(word) is true. I don't know what bloom filters are, so I'm not saying this answer is better than them -- but after I suggest that instead of imposing some other restriction, ask me to think about what is wrong with my answer. Talk to me about the false-positives/false-negatives [or lack thereof]. Talk to me about what hash function I could use. Or about why I picked that way. Or what problems could happen if the hash function wasn't perfectly uniform.

[dangoldin]

Fair points but I don't expect people to get to the Bloom filter on their own - I view as more of a process that both of us are driving towards. I also enjoy hearing new solutions - there's always room for discussion and I will try to dig deeper into answers if I sense something is wrong.

At the end I do like to get to the Bloom filter piece though in order to see what the response is as well as talk about something that is new to them.

[charrington]

How about just going with the disk-based line if the candidate goes there? On-disk data structures is a rich area for exploration. I think you're getting people a little riled up here because you seem to want to discuss Bloom filters no matter what. You seem to grok that this should be about thinking skills, data structures, and algorithms. That's great. Forcing the candidate to go where you have a particular interest is not so great.

[dangoldin]

Unfortunately I myself am not too familiar with on-disk data structures and wouldn't be too comfortable interviewing based on that. It probably is something I should brush up on but for the specific role I've been interviewing for it doesn't seem to be a big need.

[Stormbringer]

Good luck with your spell checkers for tightly RAM limited devices with no persistent storage and no external hard drives...

Frankly, I'm surprised and amazed that there is still a market for modding old Tamagotchis. Human ingenuity is amazing.