[ant6n]

Yes but is it Referring to the additive or multiplicative inverse?

Or maybe it’s making the tree upside down, so all leaves become roots, and the root becomes a leaf. But when we do that, do we just invert all the edges or transform the whole tree?

Maybe it’s referring to changing a red-black tree into a green-white tree? Or turning a splay tree into a merge tree?

[monocasa]

It can mean a lot of things, so you ask questions.

Howell (the homebrew 'google didn't hire me because of inverting a binary tree' guy) confirmed that they meant swapping right and left children of all nodes.