package t234;

/**
 * This is an object-oriented implementation 2-3-4 trees using the
 * state design pattern. 
 *
 * The classic discussion for 2-3-4 trees is outlined in Sedgewick's
 * "Algorithms in C++", Addison-Wesley 1992, pp. 215-219.
 * Other elucidating discussions of balanced trees can
 * be found in Stubbs and Webre's "Data Structures",
 * and Aho, Hopcroft and Ullman's "Data Structures and Algorithms".
 *
 * @since 04/18/01
 * @author Dung X. Nguyen, Copyright 2000 - All Rights Reserved.
 * @author Alan L. Cox
 */
public class Tree234
{
  private ANode234 _rootNode;

  /**
   * Initializes this Tree234 to empty.
   */
  public Tree234()
  {
    _rootNode = EmptyNode.Singleton;
  }

  /**
   * Initializes this Tree234 to contain exactly one data element, an
   * empty left subtree, and an empty right subtrees.  The subtrees
   * are Tree234. 
   *
   * This constructor is not intrinsically needed.  It exists as a
   * convenience only. 
   *
   * @param n != null.
   */
  public Tree234(Integer n)
  {
    _rootNode = new Node2(n);
  }

  public final boolean isEmpty()
  {
    return _rootNode.isEmpty(this);
  }

  /**
   * Inserts an Integer into this Tree234 without duplication.
   *
   * @param n != null.
   */
  public final void insert(Integer n)
  {
    _rootNode.insert(this,n);
  }

  /**
   * For debugging purpose.
   * EXERCISE FOR STUDENTS: Write the toString() method instead.
   *  Hint: see the binary tree example.
   */
  public final void draw()
  {
    drawAtLevel(0);
  }

  ///////////////////////////////////////
  //Not visible outside of package

  Tree234(ANode234 root)
  {
    _rootNode = root;
  }

  Tree234(Tree234 lTree, Integer n, Tree234 rTree)
  {
    _rootNode = new Node2(lTree, n, rTree);
  }

  final void drawAtLevel(int level)
  {
    _rootNode.drawAtLevel(level);
  }

  final void changeRoot(ANode234 newRoot)
  {
    _rootNode = newRoot;
  }

  final ANode234 root()
  {
    return _rootNode;
  }

  final void insertHelper(Tree234 parent, Integer n)
  {
    _rootNode.insertHelper(parent, this, n);
  }

  final void attach(Tree234 lTree, Integer n, Tree234 rTree)
  {
    _rootNode.attach(this, lTree, n, rTree);
  }
}