package structure;

class BTInorderIteratorR implements Iterator
{
    //+implementation
    protected BinaryTreeNode root; // root of traversed subtree
    protected Queue todo;  // queue of unvisited elements

    public BTInorderIteratorR(BinaryTreeNode root)
    // post: constructs an iterator to traverse in inorder
    {
	todo = new QueueList();
	this.root = root;
	reset();
    }	

    public void reset()
    // post: resets the iterator to retraverse
    {
	todo.clear();
	enqueueInorder(root);
    }
    
    protected void enqueueInorder(BinaryTreeNode current)
    // pre: current is non-null
    // post: enqueue all values found in tree rooted at current
    //       in inorder
    {
	if (current == null) return;
	enqueueInorder(current.left());
	todo.enqueue(current);
	enqueueInorder(current.right());
    }
    //-implementation

    //+prePost
    protected void enqueuePreorder(BinaryTreeNode current)
    // pre: current is non-null
    // post: enqueue all values found in tree rooted at current
    //       in preorder
    {
	if (current == null) return;
	todo.enqueue(current);
	enqueuePreorder(current.left());
	enqueuePreorder(current.right());
    }

    protected void enqueuePostorder(BinaryTreeNode current)
    // pre: current is non-null
    // post: enqueue all values found in tree rooted at current
    //       in postorder
    {
	if (current == null) return;
	enqueuePostorder(current.left());
	enqueuePostorder(current.right());
	todo.enqueue(current);
    }
    //-prePost


    public boolean hasMoreElements()
    // post: returns true iff iterator is not finished
    {
	return !todo.isEmpty();
    }

    public Object value()
    // pre: hasMoreElements()
    // post: returns reference to current value
    {	
	return ((BinaryTreeNode)todo.peek()).value();
    }

    //+implementation
    public Object nextElement()
    // pre: hasMoreElements();
    // post: returns current value, increments iterator
    {
	BinaryTreeNode current = (BinaryTreeNode)todo.dequeue();
	return current.value();
    }
    //-implementation
}