It doesn't matter if the solution is publicly available - if their interview process is based on the assumption that the candidate is completely unaware of the

It doesn't matter if the solution is publicly available - if their interview process is based on the assumption that the candidate is completely unaware of the problem, this method neglects the (more common) case of a candidate asking other people in her network who've interviewed at Airbnb what happens in the interview. In the interviews I've done, I have actually had a recruiter (Robert Half Technologies) ask the candidate about the interview, the candidate discusses my coding challenge with the recruiter afterward, and then the recruiter made sure all other candidates knew of the problem long before my interview so they could be prepared. My solution has been to have a multi-stage problem that shifts in an unexpected way - if from the 1st stage the candidate anticipates my "plot twist" I end the interview because they've been caught cheating (think "Design a car" and then later "turn this car into a boat" - if from stage 1 the car has boat-like tendencies, they're cheating.)