I assumed it as taking a binary tree (L|R) and reproducing a tree that's (R|L). And if it is that, then writing out the algorithm on a back of a napkin just now

I assumed it as taking a binary tree (L|R) and reproducing a tree that's (R|L). And if it is that, then writing out the algorithm on a back of a napkin just now was a pretty thought provoking exercise :)