So a lot of the more complicated DS&A questions seem ridiculous, but I had to check on "inverting a binary tree" to see if it was really as simple as it sounded

So a lot of the more complicated DS&A questions seem ridiculous, but I had to check on "inverting a binary tree" to see if it was really as simple as it sounded. It is. Just swap left and right, recursively. It's one of the easiest possible tests of being able to grok recursion[0]. You should be able to do this, even if you're self-taught or early in a college degree program. Am I missing something? The only excuse I can imagine is interview anxiety, which is a real problem that deserves accommodation (bad explanations of the problem may play a role too, but you should be able to ask good clarifying questions). But if someone is really incapable of this very minor feat of programming, then I'm sorry but an interview process is right to reject them. [0] Even if you don't literally write recursive Java methods, which you probably shouldn't, understanding recursive logic is critical all over the tech stack.