Yes, and I think the appropriate response is to rate-limit the interviews to one that you can handle easily. 1/week? Employers typically have pipelines designed for hiring throughput, so they won't mind spacing out stages longer (modulo any recruiter metrics, but I haven't heard of a case of that).
And as they're all similar style questions, they should just read up on these. Hold off on interviews until you're confident, or just schedule the less-desirable firms first, so that you have enough time to read up.
Interviewees know that these questions are coming, they can control the schedule, and they're the only ones who know their own energy and state. Nobody tells them that it's up to them to do flow control. But it's a hot market and people want good programmers. Even if you don't do tree searches or inversions in your normal work day, you can show that you're good because you can understand this stuff. Most candidates can't. So please, take your time, skim the textbooks, take a few notes, maybe do a few flash cards.
