Dancing Links - Donald Knuth - http://arxiv.org/abs/cs/0011047 http://arxiv.org/abs/cs/0011047 Lots of fun and is a weekender, but you can expand it to solve a

Dancing Links - Donald Knuth - http://arxiv.org/abs/cs/0011047 http://arxiv.org/abs/cs/0011047 Lots of fun and is a weekender, but you can expand it to solve anything from sudoku to all kinds of tiling problems. David Goodger's webpage, http://puzzler.sourceforge.net/ http://puzzler.sourceforge.net/, solves all sorts of polyform puzzles using DLX algorithm.