//To Sort
public ArrStack <Key> keys()
{
ArrStack <Key> q = new ArrStack <Key>(100);
inorder(root, q);
return(q);
}
private void inorder(Node x, ArrStack <Key> q)
{
if (x == null)
{
return;
}
inorder(x.left, q);
q.push(x.key);
inorder(x.right, q);
}