Welcome to your interview.
The question is on your right: Closest Value in BST. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
Given a binary search tree (BST), write an efficient algorithm to find the closest node value to a target number.