Representing sparse integer sets?

Question

What is a good way to represent sparse set of integers (really C memory addresses) in a compact and fast way. I already know about the obvious things like bit-vectors and ru

Answer 1

You are referring to a judy array. It was a HP project. I think they are used in ruby and are available in c. Very interesting data structure. Making use of the fact that allocations are (at least) word aligned, having separate structures for dense and sparse ranges.

http://judy.sourceforge.net/index.html