// file: BTree.java
// The next node is inserted at the 'right most' location,
// that is, the tree is always a full binary tree.
// dec-06-1998
class BTree 
{
    private BinNode root;
    private BinNode curr;

    public BTree()
    {
	root = null;
	curr = root;
    } // BTree

    public void insert(Object it)
    // insert 'it' as child of 'curr'
    // if 'curr' is full (i.e. has both children
    // go to its sibling
    {
	BinNodePtr newNode = new BinNodePtr(it);
	if (root == null) // brand new
	{
	    root = newNode;
	    curr = root;
	}
	else
	{
	    if (curr.left() == null)
		curr.setLeft(newNode);
	    else if (curr.right() == null)
	    {
		curr.setRight(newNode);
		// after this insertion, we have to repoint the 'curr'
                if (curr == root) // easy
		    curr = curr.left();
		else
		    curr = rightSibling();
	    }
	}  // else
    }  // insert

    private BinNode rightSibling()
    {
	LQueue queue = new LQueue();
	BinNode help = root;

	queue.enqueue(help);
	while (queue.isEmpty() == false && help != curr)
	{
	    help = (BinNode)queue.dequeue();
	    if (help.left() != null)
		queue.enqueue(help.left());
	    if (help.right() != null)
		queue.enqueue(help.right());
	}
	if (help == curr)
	    return (BinNode)queue.dequeue();
	else
	    return null;   // this should neven happen
    } // rightSibling


    public void print()
    // print in pre-order
    {
	preorder(root);
    }

    private void preorder(BinNode p)
    {
	if (p == null) return;
	System.out.print((String)p.element() + " ");
	preorder(p.left());
	preorder(p.right());
    }
} // BTree