Code for 01 mar.

2016-03-01/BST.hs

@@ -0,0 +1,32 @@
+module BST where
+
+data BST = EmptyNode | Node BST Int BST deriving (Show, Eq)
+
+inOrder :: BST -> [Int]
+inOrder EmptyNode    = []
+inOrder (Node l v r) = inOrder l ++ [v] ++ inOrder r
+
+find :: BST -> Int -> Bool
+find EmptyNode _ = False
+find (Node l v r) x
+  | x == v    = True
+  | x > v     = find r x
+  | otherwise = find l x
+
+insert :: BST -> Int -> BST
+insert EmptyNode x = Node EmptyNode x EmptyNode
+insert node@(Node left value right) x
+  | x < value = Node (insert left x) value right
+  | x > value = Node left value (insert right x)
+  | otherwise = node
+
+fromList :: [Int] -> BST
+fromList []       = EmptyNode
+fromList (first : rest) = insert (fromList rest) first
+
+isBST :: BST -> Bool
+isBST EmptyNode = True
+isBST (Node EmptyNode _ EmptyNode) = True
+isBST (Node l@(Node _ lv _) v EmptyNode) = lv < v && isBST l
+isBST (Node EmptyNode v r@(Node _ rv _)) = rv > v && isBST r
+isBST (Node l@(Node _ lv _) v r@(Node _ rv _)) = lv < v && v > rv && isBST l && isBST r