I think being able to code a binary tree is a good indication of competence. C is perhaps an exception where writing a tree implementation is much harder due to

I think being able to code a binary tree is a good indication of competence. C is perhaps an exception where writing a tree implementation is much harder due to pointer syntax and memory unsafety. Some people freeze up during interviews and are not able to code as good as they otherwise could. That is unfortunate and a problem I don't know how to solve.