I've been hooked on Queens puzzles (https://www.linkedin.com/games/queens/) for the last few months, and decided to try and build a solver for them.

Rather than doing a traditional solution search, I tried to model it instead on how humans solve these puzzles, iteratively eliminating and confirming possible squares for Queens.

And since this was a side-project, I decided to go overboard, and try and make it as fast as possible (avoiding HashMap/HashSet in favor of bit fields, for example).