An interesting supplemental reading is the "two bowling balls" interview puzzle -- http://20bits.com/articles/interview-questions-two-bowling-balls/ http://20bi

An interesting supplemental reading is the "two bowling balls" interview puzzle -- http://20bits.com/articles/interview-questions-two-bowling-balls/ http://20bits.com/articles/interview-questions-two-bowling-b... It's essentially a 2 level skip list (but could be generalized where you get one extra level per bowling ball), and brings out some basic calculus to optimize lookup performance even further.