A big collection of data structures and algorithms puzzles. As on May 2013, the repository has roughly 130 problems with solutions.
Solutions are primarily in Java (under java/). Some solutions are in Ruby (under ruby/).
Problem statements are specified as Javadoc at the top of every solution. I have tried to be as descriptive as I can, but if something is not clear then please do let me know! Problems are broadly classified into the following categories which are self explanatory.
Please feel free to contribute!