// 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

class TTNode {              // 2-3 tree node implementation
  private Elem lkey;        // The node's left key
  private Elem rkey;        // The node's right key
  private int numKeys;      // Number of key values stored
  private TTNode left;      // Pointer to left child
  private TTNode center;    // Pointer to middle child
  private TTNode right;     // Pointer to right child

  public TTNode() { center = left = right = null; numKeys = 0; }
  public TTNode(Elem l, Elem r, TTNode p1, TTNode p2, TTNode p3) {
	lkey = l; rkey = r;
	if (r == null) numKeys = 1; else numKeys = 2;
	left = p1; center = p2; right = p3;
  }

  // Add key and subtree to internal node
  public void addKey(Elem val, TTNode child) {
    Assert.notFalse(numKeys==1, "Illegal addKey");
    numKeys = 2;
    if (val.key() < lkey.key()) {
      rkey = lkey; lkey = val;
      right = center; center = child;
    }
    else { rkey = val; right = child; }
  }

  public int numKeys() { return numKeys; }
  public TTNode lchild() { return left; }
  public TTNode rchild() { return right; }
  public TTNode cchild() { return center; }
  public TTNode setCenter(TTNode val) { return center = val; }
  public Elem lkey() { return lkey; }  // Left key value
  public Elem rkey() { return rkey; }  // Right key value
  public boolean isLeaf() { return left == null; }

  public void setLkey(Elem val) { // Change left key
    Assert.notFalse(val!=null, "Can't nullify left value");
    lkey = val;
  }

  public void setRkey(Elem val) { // Change right key
    Assert.notFalse(numKeys!=0,"Can't set right key of empty node");
    if ((val == null)&&(numKeys == 2)) // Clear subtree
      {right = null; numKeys = 1;}
    rkey = val;
  }

  public String toString() {
	if (numKeys==1) return lkey.toString();
	else return lkey.toString() + " | " + rkey.toString();
  }
} // class TTNode