Welcome to your interview.
The question is on your right: Tree Traversal for Hierarchical Data. 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.
Perform a tree traversal, such as depth-first or level-order, to extract and format hierarchical data from a custom tree structure.