Move traversal methods to BinaryTreeADT.

Author: happy-san

Diff for: lib/trees/binary_tree_adt.dart

@@ -38,21 +38,21 @@ abstract class BinaryTreeADT<N extends BinaryNodeADT, V extends Comparable>
   @override
   void nullify() => root = null;
 
-  @override
+  /// In Order Traversal.
   List<V> inOrder() {
     var result = <V>[];
     _inOrder(root, result);
     return result;
   }
 
-  @override
+  /// PostOrder Traversal.
   List<V> postOrder() {
     var result = <V>[];
     _postOrder(root, result);
     return result;
   }
 
-  @override
+  /// PreOrder Traversal.
   List<V> preOrder() {
     var result = <V>[];
     _preOrder(root, result);

Diff for: lib/trees/tree_adt.dart

@@ -28,15 +28,6 @@ abstract class TreeADT<N extends NodeADT, V extends Comparable> {
   /// Deletes [value] from the tree and updates it's [root].
   void delete(V value);
 
-  /// In Order Traversal.
-  List<V> inOrder();
-
   /// Empty the tree.
   void nullify();
-
-  /// PostOrder Traversal.
-  List<V> postOrder();
-
-  /// PreOrder Traversal.
-  List<V> preOrder();
 }