// Source code example for "A Practical Introduction
// to Data Structures and Algorithm Analysis"
// by Clifford A. Shaffer, Prentice Hall, 1998.
// Copyright 1998 by Clifford A. Shaffer

public class TTtree { // 2-3 Tree node class.  Similar to BST in capabilities.
  private TTNode root;

  public TTtree() { root = null; }
  public void clear() { root = null; }

  public void insert(Elem it) {
	System.out.println("Insert: " + it);
    int retval;             // Smallest value in newly created node
    TTNode retptr = null;    // Newly created node
    Object[] temp = inserthelp(root, it);
	if (root == null) root = (TTNode)temp[0];
    else if (temp != null)    // Root overflowed: make new root
      root = new TTNode((Elem)temp[0], null, root, (TTNode)temp[1], null);
  }

  public void remove(int key) { }

  public Elem find(int key) {
	return findhelp(root, key);
  }

  public boolean isEmpty() { return root == null; }

  public void print() {
    if (root == null) System.out.print("The 2-3 Tree is empty.");
    else printhelp(root, 0);
  }

private Object[] inserthelp(TTNode rt, Elem val) { // Do insert
  if (rt == null) { // Empty tree.
    rt = new TTNode(val, null, null, null, null);
    Object[] temp = {rt};  return temp;
  }
  if (rt.isLeaf())  // At leaf node -- insert here
    if (rt.numKeys() == 1) // Easy case
      { rt.addKey(val, null);  return null; }
    else return splitnode(rt, val, null);
  // Now at Internal node
  Object[] retval;                 // Hold result from insert
  if (val.key() < rt.lkey().key())
    retval = inserthelp(rt.lchild(), val);
  else if((rt.numKeys() == 1) || (val.key() < rt.rkey().key()))
    retval = inserthelp(rt.cchild(), val);
  else retval = inserthelp(rt.rchild(), val);
  if (retval == null) return null; // No split of child node
  // If here, child node split
  if (rt.numKeys() == 1) {         // Just add to rt
    rt.addKey((Elem)retval[0], (TTNode)retval[1]);
    return null;                   // No further splitting
  }
  // Split this node as well
  return splitnode(rt, (Elem)retval[0], (TTNode)retval[1]);
}

// Split a node into two; return info on promoted value
Object[] splitnode(TTNode rt, Elem val, TTNode child) {
  Object[] temp = new Object[2];   // Store info to be returned
  if (val.key() > rt.rkey().key()) { // Val is rightmost
    temp[0] = rt.rkey();           // Promote old right key
    TTNode hold = rt.rchild();
    rt.setRkey(null);              // Clear it
    temp[1] = new TTNode(val, null, hold, child, null);
  }
  else if (val.key() > rt.lkey().key()) { // Middle
    temp[0] = val;                 // Promote val
    temp[1] = new TTNode(rt.rkey(), null, child, rt.rchild(), null);
    rt.setRkey(null);              // Clear it
  }
  else {                           // Val is leftmost
    temp[0] = rt.lkey();           // Promote old left key
    temp[1] = new TTNode(rt.rkey(), null, rt.cchild(),
                         rt.rchild(), null);
    rt.setCenter(child);  rt.setLkey(val);
    rt.setRkey(null);              // Clear it
  }
  return temp;          // Return promoted element and its subtree
}
private Elem findhelp(TTNode root, int val) {
  if (root == null) return null;            // val not found
  if (val == root.lkey().key()) return root.lkey(); // val found
  if ((root.numKeys() == 2) && (val == root.rkey().key()))
    return root.rkey();
  if (val < root.lkey().key())              // Search left subtree
    return findhelp(root.lchild(), val);
  else if (root.numKeys() == 1)             // Search center subtree
    return findhelp(root.cchild(), val);
  else if (val < root.rkey().key())         // Search center subtree
    return findhelp(root.cchild(), val);
  else return findhelp(root.rchild(), val); // Search right
}

private void printhelp(TTNode rt, int level) {
  for (int i=1; i<=level; i++) System.out.print("  ");
  if (rt == null) {
	System.out.println("null");
	return;
  }
  System.out.println(rt);
  if (rt.isLeaf()) return;
  printhelp(rt.lchild(), level+1);
  printhelp(rt.cchild(), level+1);
  printhelp(rt.rchild(), level+1);
}

}