I think most people here miss the point, thinking that they need to know about symmetric binary trees in order to be able to answer such questions.<p>These kind of tests are aiming to find developers who can think out of the box and start solving problems they haven&#x27;t heard of before. This is quite a simple problem to solve if you start thinking about it. If you get stuck because of the binary tree and because you&#x27;ve never done that before, then I believe you would be a mediocre dev (which is not a problem in many companies).