This is excellent advice!
Being an interviewer myself I value personality traits like good listening, being able to collaborate and open mindedness way more than having having some specific knowledge.
Candidates often assume that they're only being evaluated for what they know or don't which is a mistake. To me, the kind of person and professional they are is way more important.
Being asked to throw some code on a whiteboard isn't some kind of red flag though ?
First of, as you mention, it's hard to focus when under stress from the interview. Then, company should be looking for people knowing how to learn not people knowing one solution.
I think the whiteboard coding interview can be quite successful /if it is done well/. Which it unfortunately often isn't.
It ought to feel like a collaboration. Your interviewer's goal should be to get a taste for what it would feel like if they were stuck on a problem and asked you to grab a whiteboard with them and map it out together.
In that configuration, it's not about the candidate having all the answers right away. It's about their ability to communicate and take little ideas that you feed them and build on them.
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