data Tree a = Nil
			| Leaf a
			| Node a (Tree a) (Tree a)

root Nil = undefined
root (Leaf x) = x
root (Node x _ _) = x

left Nil = undefined
left (Leaf _) = Nil
left (Node _ branch _) = branch

right Nil = undefined
right (Leaf _) = Nil
right (Node _ _ branch) = branch


tree = Node 1 (Node 2 (Leaf 10) (Leaf 11)) (Node 5 Nil (Leaf 4))


preord Nil = []
preord n = (preord $ left n) ++ 
			[(root n)] ++
			(preord $ right n)
-- cu ++ (root n) ++ vezi eroare tip la preord tree


-- BFS
bfs tree = bfsR [tree]

-- pe frontiera
bfsR [] = []
bfsR (Nil : open) = bfsR open
bfsR (n : open) =
	(root n) : bfsR (open ++ [cL, cR])
		where {cL = left n; cR = right n}
	
	
	
	
	









	
-----------------------------

theGraph = [(1, 2), (1, 4), (2, 1), (2, 3),
            (3, 5), (3, 6), (5, 6), (6, 1)]