I don't ask questions that can only be solved with some clever trick. In my experience, I get the most signal by posing a question that has many solutions of v

I don't ask questions that can only be solved with some clever trick. In my experience, I get the most signal by posing a question that has many solutions of varying degrees of efficiency. This way anyone except the least qualified candidates can make some meaningful progress. I then gently guide the candidate to help them produce the best solution they're capable of in the allotted time. I then score the interview on the basis of where they have landed, the process by which they got there and how much help they needed along the way (and of course the role/level they're interviewing for).