Swift Book Club Book?

My co-worker Curt Clifton writes:

I’d like to start a “bike shedding” club. One problem a week, everybody implements a solution in Swift. Get together and compare approaches.

Anybody have a good source of sample problems? Project Euler is probably too mathy. Maybe a data structures book?

This would be for programmers at Omni, so think of the kinds of problems that people writing large Mac and iOS productivity apps need to solve.

(And reply to Curt on Twitter if you have a good idea. Thanks!)