Comment by kele

> First, you can't invert a binary tree (as in flip upside down). If you did, you'd end up with multiple roots and since all binary trees are rooted, you'd no longer have a binary tree. It'd be a tree, just not a binary tree

Just because someone wrote on Twitter with limited number of characters that the problem was to "invert a binary tree", does not mean there were no clarification from the recruiter.

> And if they actually meant for you to recurse down and swap left and right on everything, it would dramatically lower my opinion of them because it would make me wonder if they knew the difference between how a binary tree is drawn on a whiteboard vs. how it is laid out in memory.

If you're thinking about making a real structure, I believe you should recurse down and swap. If you don't do this, rotating, joining etc, could be a real pain.