If it is a "toy" question, then I'm of two minds about it:
On one hand, I am used to solving higher level problems, so it might take me a few minutes just to realize you are asking a much simpler question. It also can feel just a tad insulting to be drilled on CompSci 101 questions.
Oh the other hand, I think candidates should be able to solve such questions, as long as the scope is clear. You need to filter somehow and I've met people who could not do that.