Zigzag

import Prelude hiding (Left, Right)

data Tree a = Empty | Node a (Tree a) (Tree a) deriving (Show)
data Direction = Left | Right

computeZigzag::Tree a->Int->Direction->[Int]
computeZigzag Empty _ _ = [0]
computeZigzag (Node _ Empty Empty) current _ = [current]
computeZigzag (Node _ left right) current Left = computeZigzag left current Left ++ computeZigzag right (current + 1) Right
computeZigzag (Node _ left right) current Right = computeZigzag left (current + 1) Left ++ computeZigzag right current Right

zigzag::Tree a->Int
zigzag (Node  _ left right) = maximum(computeZigzag left 0 Left ++ computeZigzag right 0 Right)