@Override
    public Iterator<E> iterator() {
      int expectedModCount = modCount;
       return new Iterator<E>() {
        BinNode<E> curr = root;
        @Override
        public boolean hasNext() {
            return curr != null;
        }

        @Override
        public E next() {
            checkModCount();
            //todo
             return ;
        }


        private void checkModCount() {
            if (expectedModCount != modCount) {
                throw new ConcurrentModificationException();
            }
        }
    };
}

class Node {
     Object value;
     Node left, right;
}

void go(Node root) {
    go(root.left);
    go(root.right);
}

class NodeIterator implements Iterator {
    Stack<Node> nodes;

    public NodeIterator(Node root) {
         nodes.push(root);
    }
    boolean hasNext() {
         return nodes.size > 0;
    }
    Object next() {
         Node current = nodes.peek();
         if (current.left != null)
             nodes.push(current.left);
         else if (current.right)
             nodes.push(current.right);
         else
             nodes.pop();
         return current.value;
    }
}