Nobody in this thread has even been able to define what inverting a tree means. (Reversing or mirroring? Sure.) My search for how to invert a tree led to a bunc

Nobody in this thread has even been able to define what inverting a tree means. (Reversing or mirroring? Sure.) My search for how to invert a tree led to a bunch of fairly hairy academic papers. If you have a definition, please elucidate.