DJ Ape .Net – The Home of Perfect Sudoku

Good news folks!

The Washington Post have decided to restart printing my Samurai Sudoku puzzles in their Comics section of the Sunday issue… thanks to YOU! Apparently the readers have been clamoring for the return of Samurais and the editors had no other choice but to change their minds only a month after they decided to stop.

This makes me really proud and I don’t know how to thank you folks.

I’m still uncertain when precisely will the first puzzle be printed, but I think it will be 10 days from now, on Sunday, February 14. Stay tuned for confirmation of this.

UPDATE: I just found out that The Washington Post will restart with my Samurais on Sunday, February 28, 2010!

Barnes & Noble have started selling my books, so if any of you prefer to purchase from them, go ahead! They are even giving some really good discounts (30%+) on some of the books and at least 10% on all of them, so it’s worth going for!

Just click on the Barnes&Noble image to the right:

Here is something new (for this site) for the New Year: Outside Sudoku. This puzzle is also shown today on the Daily Sudoku page, but I thought I should properly introduce it.

The rules:
1. For the 9×9 grid all standard Sudoku rules apply. However, you don’t have any starting clues in there!
2. The clues are given outside the grid. 0, 1, 2 or 3 numbers are shown.
3. These clues tell you which numbers appear in the 3 closest cells in the grid, IN ANY ORDER (not necessarily in the order they are given in). In other words, the clues for a row tell you which numbers appear in the corresponding row and the closest nonet (3×3 box). Same for columns.

I hope you will like it. I might start including them on the Daily Sudoku page, of course in some variant version (the non-consecutive type looks particularly interesting).

Bad news folks, I’m afraid: the Samurai Sudoku puzzle printed in the Comics section of The Washington Post on Sunday, December 27, 2009, would’ve been the last Samurai puzzle printed in this newspaper. After four years and more than 200 Samurai puzzles, they have decided to stop this feature.

From the editor: “The change is part of a larger agreement … and is not a result of any dissatisfaction with your puzzle.”

On the other hand, my Samurai puzzles will continue to feature in the Washington Express (the free newspaper) every Friday.

As a reminder to those who enjoy my Samurais, you can find two of them every week on the Samurai Sudoku page.

Or, you can order my books with Samurai puzzles here:

Here is a Christmas gift for you! Just in time for the holiday season, three new books have been published on Amazon:

That’s right, I listened to your requests and have prepared a book full of only ZERO Killers and nothing else!

These books will NOT be published through LuLu!

This should take you through the holiday season.

Dear visitors, I am performing some site maintenance at the moment. You may experience some problems accessing the site. It shouldn’t take long. Thank you for your patience!

…

The site was down for less than half an hour. Everything should appear as before. A new version of Wordpress has been installed.

If you encounter any problems navigating the site, please let me know!

Thanks and sorry for the inconvenience!

With a couple of months delay, I’ve created my first newsletter. It is available here.

These newsletters will be sent out monthly by e-mail to those who sign up. You can sign up by submitting your e-mail address in the box in the left-hand navigation pane (above the book cover pages) or by sending me an e-mail.

Another addition to my portfolio of various number/logic puzzles are Nurikabe puzzles.

I think these puzzles are being undeservedly somewhat neglected in the puzzle world and I intend to change that. The number of solving techniques and approaches that can be found in Nurikabe puzzles far exceeds any other puzzle type. For me it was a challenge programming a solver and a generator of Nurikabe puzzles, much more than programming all other puzzles so far.

Goal:
For each cell, determine if it must be white (draw a circle in it) or black (paint it).

There are two types of Nurikabe jargon:
1) White cells are walls, black cells are a maze.
2) White cells are islands, black cells are a stream.

The Rules of Nurikabe:
1. Cells with numbers (initial clues) are always white.
2. 2×2 (or bigger) blocks of black cells are not allowed.
3. All black cells must be connected orthogonally (horizontally or vertically). In other words: there is a maze between the walls. Or: A stream runs between the islands.
4. The initial numbers (clues) indicate how many white cells are orthogonally connected with the cell that contains the number (including that cell). In other words: the numbers indicate how big each island is; or again, how big each wall is.
5. White cells that “belong” to two different clues must be separated by black cells. In other words: two islands cannot touch each other, there must be some water between them. Or, two walls must be separated by the maze.
6. Nurikabe puzzles can be of any size.

And finally, here is the puzzle. I’m still working on automagically determining the difficulty of these puzzles, but I think this one is quite tough.

Nurikabe 12×12 for July 20, 2009.
Click to download the puzzle in your favorite format:

png solution – final

Folks, I’d really like to hear what you think of Nurikabe puzzles in general and about this particular puzzle (the difficulty in first place). So, please do post your comments!