As an interviewer, you're not looking for a solution; it's supposed to be an ice-breaker, to get a technical conversation going. Doesn't always work, but good

As an interviewer, you're not looking for a solution; it's supposed to be an ice-breaker, to get a technical conversation going. Doesn't always work, but good enough. (OTOH, if the interviewer has no idea why they're asking this, and they're just blindly checking off boxes from "The Greatest Checkbox List For Interviewers (tm)", it will fail like any other tool wielded by a clueless user. A very specific failure mode here is "THE BOOK has The One True Solution, and I'm expecting you to read my mind and choose this.")