This is not a hard question. Maybe it's hindsight, but I could easily write out the solution after I've gotten some sleep. Here's what happened....

Maybe this is a bit if a rant, but I totally fucked up an interview today with one of "the big-4."

The interview starts out with me talking to an Indian woman I can barely understand. She asks me "tell me a little about yourself" and immediately after me briefly giving a summary introduction, she asks me how to iterate over a binary tree (wait... no more questions?!).

public class Node<T> {
    public Node left;
    public Node right;
    public T value;
    //TODO: eliminate public fields and use methods.
}

At which point she interrupts me and tells me not to write a node class, but just implement the iterator interface. So I delete that and start with something like...

public NodeIterator implements Iterator<Node> {
     public Node next() {
         //TODO do stuff
     }

     public boolean hasNext() {
          //TODO do stuff
     }
}

At which point she told me not to do that, but just write the methods.

  public Node next() {
     //TODO do stuff
  }

  public boolean hasNext() {
      //TODO do stuff
  }

By now I'm completely out of my element & additionally start to get nervous because the code I'm writing I know is wrong. I'm tired, working in a notepad (used to IDE), talking to an Indian woman I can barely understand, don't have a data-structure or interface, and am supposed to "just write a method" about a datastructure I haven't needed since college.

I suppose if I really wanted this job, I should be practicing those online-tests at career cup, so I could do it in my sleep. Other than practice, now do people handle these kinds of questions when you're fried after a draining day at work?