In view of the nature of the symmetry , it is natural to call (X) the transpose
of X and [ (X)] the transpose of [X]. So we use the notation [X]T = [ (X)]. Thus
[X]T is obtained from [X] by switching its two entries. Now, if mini-Sudokus X and
Y are H-equivalent, then X is R C-equivalent to Y or to (Y). We therefore say
that [X] and [Y] are H-equivalent if [X] = [Y] or [X] = [Y]T . Dene [X]H to be the H-
equivalence class of [X]. Note that we now have two H-equivalences: H-equivalence
of mini-Sudokus and H-equivalence of partition types.