Вот мне предложили решение
| Код |
data BinTree a = Nil
| Node a (BinTree a) (BinTree a)
deriving (Eq, Show)
maxLabel :: (Eq a) => BinTree a -> Maybe a
maxLabel Nil = Nothing
maxLabel tree = Just ml
where (ml, _) = foldl1 maxLabelOcc . countLabels . labels $ tree
maxLabelOcc l1@(_, c1) l2@(_, c2) =
if c1 > c2 then l1 else l2
labels :: BinTree a -> [a]
labels Nil = []
labels (Node x l r) = x : labels l ++ labels r
countLabels :: (Eq a) => [a] -> [(a, Int)]
countLabels list = map cnt list
where cnt x = (x, foldl (\acc el -> acc + if x == el then 1 else 0) 0 list)
|
Я его подправил, но что-то не то =(
| Код |
data BinTree a = Nil | Node a (BinTree a) (BinTree a) | Leaf a
maxLabel :: (Eq a) => BinTree a -> Maybe a
maxLabel Nil = Nothing
maxLabel tree = Just ml
where (ml, _) = foldl1 maxLabelOcc . countLabels . labels $ tree
maxLabelOcc l1@(_, c1) l2@(_, c2) =
if c1 > c2 then l1 else l2
labels :: BinTree a -> [a]
labels Nil = []
--labels (Leaf x) = x
labels (Node x l r) = x : labels l ++ labels r
countLabels :: (Eq a) => [a] -> [(a, Int)]
countLabels list = map cnt list
where cnt x = (x, foldl (\acc el -> acc + if x == el then 1 else 0) 0 list)
tree = Node "alpha" (Leaf "alpha") (Node "beta" (Leaf "gamma") (Leaf "delta"))
main = print $ maxLabel tree
|
помогите подправить |
