// 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

// Implementation of General Tree Nodes:
// Left Child/Right Sibling implementation (with parent pointer)
public class GTNodeImpl implements GTNode {

private GTNode rent;
private GTNode leftchild;
private GTNode rightsib;
private Object element;

public GTNodeImpl(Object value) { // constructor with no context
  rent = leftchild = rightsib = null;
  element = value;
}

// constructor with opportunity to link into tree context
public GTNodeImpl(Object value, GTNode par, GTNode leftc, GTNode rights) {
  element = value;
  rent = par; leftchild = leftc; rightsib = rights;
}  

// Return the value
public Object value() { return element; }

// TRUE if this node is a leaf
public boolean isLeaf() { return leftchild == null; }

// Return the parent
public GTNode parent() { return rent; }

// Return the leftmost child
public GTNode leftmost_child() { return leftchild; }

// Return the right sibling
public GTNode right_sibling() { return rightsib; }

// Set the value
public void setValue(Object value) { element = value; }

// Set the parent
public void setParent(GTNode par) {rent = par; }

// Add a new leftmost child
public void insert_first(GTNode n) {
  ((GTNodeImpl)n).rent = this;
  ((GTNodeImpl)n).rightsib = leftchild;
  leftchild = n;
}

// Insert a new right sibling
public void insert_next(GTNode n) {
  ((GTNodeImpl)n).rent = rent;
  ((GTNodeImpl)n).rightsib = rightsib;
  rightsib = n;
}

// Remove the leftmost child
public void remove_first() {
  if (leftchild == null) return;
  leftchild = ((GTNodeImpl)leftchild).rightsib;
}

// Remove the right sibling
public void remove_next() {
  if (rightsib == null) return;
  rightsib = ((GTNodeImpl)rightsib).rightsib;
}

}