import Tree
import H55
import H56

symCbalTrees n
    | n `mod` 2 == 0 = []
    | otherwise = [Branch 'x' x (reverseTree x) | x <- cbalTree (n `div` 2)]

reverseTree Empty = Empty
reverseTree (Branch x l r) = Branch x (reverseTree r) (reverseTree l)

symCbalTrees' = filter symmetric . cbalTree