// 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

// A simple implementation for general trees.
// This does not really address the thornier general tree
// implementation issues, but it does is let you attach a couple
// of trees together, and it is possible to build any tree.
public class GenTreeImpl implements GenTree {

private GTNode rt;

public GenTreeImpl() { rt = null; }

public void clear() { rt = null; }

public GTNode root() { return rt; }

public void newroot(Object value, GTNode first, GTNode sib) {
  clear();
  rt = new GTNodeImpl(value, null, first, sib);
  if (first != null)
    first.setParent(rt);
  if (sib != null)
    sib.setParent(rt);
}

public void newleftchild(Object value) {
  GTNodeImpl temp = new GTNodeImpl(value, rt, null,
	                               rt.leftmost_child());
  rt.insert_first(temp);
}
}