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  1. Prepare
  2. Data Structures
  3. Trees
  4. Tree: Preorder Traversal
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Tree: Preorder Traversal

  • jmcparland
     + 0 comments

    Haskell

    It would have been nice if the problem statement gave an actual sample of the expected input data and how to parse it... Bad form, folks.

    module Main where

data Tree = Empty | Node Int Tree Tree

instance Show Tree where
    show Empty = ""
    show (Node x l r) =
        show x ++ " " ++ show l ++ show r

insert :: Tree -> Int -> Tree
insert Empty x = Node x Empty Empty
insert (Node k left right) x
    | x < k = Node k (insert left x) right
    | otherwise = Node k left (insert right x)

parseTree :: [Int] -> Tree
parseTree = foldl insert Empty

main :: IO ()
main = do
    _ <- getLine
    seq <- map read . words <$> getLine :: IO [Int]
    print $ parseTree seq