[langsamer]

I think a much better indicator of how valuable a person will be in your company is not if he can solve puzzles on the fly but how munch time he puts into coding. If a person is coding in his free time and keeping up with technology and experimenting even though his current job doesn't require it, that person is more likely to have a breadth of knowledge that will pay dividends over time. Something like that cannot be gauged by him/her solving a "reverse-linked-list" problem.

Furthermore, a person involved in the community is more likely have in-roads with other strong developers, which again might pay dividends in the future in terms of hiring.

[gcp]

In my experience interviewing candidates, the two are very strongly correlated. A person coding in a lot, including in his free time is more likely to have implemented a wide variety of things, and will be much more hands-on to solve these kind of riddles/exercises, than a person with only book knowledge who coded the same kind of stuff for years on an end.