Saturday, May 3, 2008

Impossible Sudoku

Sudoku is a very popular Japanese puzzle. You can read more about it here. I usually don't play games of any sort, including puzzles. But sometimes I find them useful as a distraction or as a good way to train the mind.
There is a very good Sudoku game available for Ubuntu (I don't know about any good one for Windows, sorry). It has puzzles at four difficulty levels and is also able to generate new puzzles.
If you are using Hardy you should already have it, otherwise simply type:

sudo aptitude install gnome-sudoku

The reason I am writing about it is that I have recently successfully solved the hardest Sudoku puzzle I have ever seen. Gnome Sudoku also calculates the difficulty score for each puzzle, the difficulty score for this one was 92%. I lately found one with even higher difficulty score (95%), but for some reason it was much easier to solve.
Overall, all Sudoku puzzles are solvable - if you know how to solve them. It is actually rather simple to solve even the most difficult Sudoku once you learn the general algorithm, but it takes a lot of time and require concentration. In the next post, An algorithm for solving Sudoku puzzles, I will write in more details about this general algorithm. Meanwhile you can try to solve the two puzzles I mentioned by yourself:

In the next post I will also post the solutions of these two puzzles.

1 comment:

Anonymous said...

They are hard, true, but I have found far harder. They have some 30 clues, wheres the conjecture is that 17 is th minimum necessary, making these seem quite generous. I solved them each using one guess as an eliminator, about 2/3 of the way through.