-- Zadanie 2.
data Tree a = Empty | Node a (Tree a) (Tree a)

depth :: Tree a -> Int
depth Empty = 0
depth (Node _ l r) = 1 + max (depth l) (depth r)

preorder :: Tree a -> [a]
preorder Empty = []
preorder (Node a l r) = [a] ++ preorder l ++ preorder r

inorder :: Tree a -> [a]
inorder Empty = []
inorder (Node a l r) = inorder l ++ [a] ++ inorder r

postorder :: Tree a -> [a]
postorder Empty = []
postorder (Node a l r) = [a] ++ postorder l ++ postorder r