I have very little love for code interviews of this kind. Here's an alternative I would propose to hiring managers:

Give the candidate a research paper in PDF, then ask them to implement the algorithm described there in code.

You get the same feedback on whether they can actually code, and what kind of code they write, but it takes the pressure off having to think of what kind of algorithm to use, what the big O complexity of it is, and a thousand other factors that will probably never relate to what their day job will consist of.