If you haven’t heard of Sudoku puzzles (数独,, sūdoku) you’ve either been sleeping under a rock or been space traveling for quite a while. These 9×9 square puzzles originating from around 1900 became an international hit in 2005. Sudokus appear in newspapers, online and special sudoku puzzle books all-over-the-world. And as if that is not yet enough Sudoku TV shows and all kinds of variants of the puzzle are made. One can solve a sudoku using logic only. Because of this computational algorithms to solve every possible Sudoku must exist. This is part one in the series on such algorithms. Read the rest of this entry »