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-- Description: A red-black tree implementation in Haskell | |
-- Author: Cedric Van Goethem | |
-- Version 1, 2013 | |
type Tree a = Node a | |
data Color = Red | Black deriving (Eq, Show) | |
data Node a = Node a Color (Node a) (Node a) | Nil deriving (Eq, Show) | |
tree :: (Ord a) => a -> Tree a | |
tree x = Node x Black Nil Nil | |
addValue :: Ord a => a -> Tree a -> Tree a | |
addValue x = addNode (Node x Red Nil Nil) | |
addNode :: Ord a => Node a -> Tree a -> Tree a | |
addNode n t = go $ addNode' n t | |
where go (Node v _ l r) = Node v Black l r | |
addNode' :: Ord a => Node a -> Tree a -> Tree a | |
addNode' Nil t = t | |
addNode' n@(Node v1 c1 l1 r1) t@(Node v2 c2 l2 r2) | |
| v1 < v2 = balance $ Node v2 c2 (addChild n l2) r2 | |
| v1 > v2 = balance $ Node v2 c2 l2 (addChild n r2) | |
| otherwise = t | |
addChild :: Ord a => Node a -> Node a -> Node a | |
addChild n Nil = n | |
addChild n t = addNode' n t | |
{- Rotations -} | |
balance :: Node a -> Node a | |
balance (Node z Black (Node y Red (Node x Red a b) c) d) = Node y Red (Node x Black a b) (Node z Black c d) | |
balance (Node z Black (Node x Red a (Node y Red b c)) d) = Node y Red (Node x Black a b) (Node z Black c d) | |
balance (Node x Black a (Node z Red (Node y Red b c) d)) = Node y Red (Node x Black a b) (Node z Black c d) | |
balance (Node x Black a (Node y Red b (Node z Red c d))) = Node y Red (Node x Black a b) (Node z Black c d) | |
balance x = x | |
{- Getters and setters -} | |
setColor :: Node a -> Color -> Node a | |
setColor Nil _ = Nil | |
setColor (Node v _ x y) c = Node v c x y | |
getLeft :: Node a -> Node a | |
getLeft (Node _ _ x _) = x | |
getRight :: Node a -> Node a | |
getRight (Node _ _ _ y) = y | |
setLeft :: Node a -> Node a -> Node a | |
setLeft (Node v c x y) o = Node v c o y | |
setRight :: Node a -> Node a -> Node a | |
setRight (Node v c x y) o = Node v c x o |
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