Even if you are self-taught, you should know what is a binary tree and how idea of reversing it applies. From there you should be able to easily come up with a makeshift algorithm or ask if you can google a solution (as this is what you would be doing at the job anyway), find best answer and then apply it to the problem. I think most important part in this job is being able to find a good solution quickly if you cannot code it straight from your head. Being offended by any question and the attitude "I did X therefore I cannot Y" is what disqualifies you. There is nothing worse than an employee who thinks they know everything or that they don't need to know something and feel too superior to ask how or to find an answer from someone else. I would suggest at least trying a therapy to get to the bottom of why you behave in such a way. Sometimes a simple change in thinking can lead to a dramatic transformation.