For interviewing, I find it most useful if we ask a question that is an algorithmic problem to solve (but we don't tell them it is a graph problem and obviously it's not something as classic as Dijkstra). Then we observe if the candidate can formulate it as such, or can formulate it as anything useful (often there are several options, e.g. some find the problem to be dynamic programming). This gives much more information about the analytical skills of the candidate than about their algorithms knowledge. In terms of knowledge, what I find useful is just to ask what is a hashtable and how it works.

Of course, there are positions where this kind of skill is unnecessary and I cannot know everything about the false negatives. But failure in these areas also correlate with poor coding skills, at least in my experience of a free hundred interviews.