OCaml 99: binary tree

Author: coderxiang

OCaml99Problems/BinaryTree/at_level.ml

@@ -0,0 +1,23 @@
+(* Collect the nodes at a given level in a list. *)
+
+type 'a binary_tree = Empty | Node of 'a * 'a binary_tree * 'a binary_tree;;
+
+let at_level tr cnt = 
+  let rec at_level_tr tr cnt acc = 
+	match tr with
+	  Empty -> acc
+	| Node (u, lc, rc) -> begin
+	  if cnt = 1 then List.rev (u :: acc) 
+	  else at_level_tr rc (cnt-1) (at_level_tr lc (cnt-1) acc)
+	end
+  in
+  at_level_tr tr cnt []
+;;
+
+
+(* Test *)
+let example_tree =
+    Node('a', Node('b', Node('d', Empty, Empty), Node('e', Empty, Empty)),
+         Node('c', Empty, Node('f', Node('g', Empty, Empty), Empty)));;
+
+at_level example_tree 10

OCaml99Problems/BinaryTree/construct_2.ml

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+type 'a bst = Empty | Node of 'a * 'a bst * 'a bst;;
+
+let rec construct l = 
+  match l with 
+	[] -> Empty
+  | x :: xs -> Node (x, construct (List.filter ((>=) x) xs), construct (List.filter ((<)
+  x) xs))
+;;
+
+(* Test *)
+construct [3;2;4;7;1]
+