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-- datatype for a tree with an integer at each leaf
data Tree = Node Tree Tree | Leaf Int

-- example of a tree
t :: Tree
t = Node (Leaf 1) (Node (Node (Leaf 2) (Leaf 3)) (Leaf 3))

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-- perform a depth-first search on a tree for a given integer
search :: Int -> [Tree] -> Bool
search n []                = False
search n ((Leaf l):ts)
    | n == l               = True
    | otherwise            = search n ts
search n ((Node t1 t2):ts) = search n (t1:t2:ts)

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