"Can you invert a binary tree?"
"I wrote a book on binary trees!"
"That's very nice. The clock is ticking, you now 19 minutes left... "
"...and that's the answer."
"Sorry...you're wrong. That's not how we solve it."
"I wrote the book on it. I just solved it for you starting from first principles. It can be used as a proof."
"Sorry...if you can't think the way we do you just won't fit in."
"Can you invert a binary tree?"
"I wrote a book on binary trees!"
"That's very nice. The clock is ticking, you now 19 minutes left... "