DJ Ape .Net – The Home of Perfect Sudoku

Finally, my latest four books are available on Amazon.com:

I promised that Hidoku puzzles will be back in one form or another… and here they are!

When I published Volume 1 of this book I did say that I was a little worried that I’d overdone the difficulty of the puzzles. And rightly so. Your comments did say that some puzzles were too challenging. Therefore, this time I have reduced the difficulty of the puzzles, but only by a notch. So, if you are new to Hidoku, I recommend trying volume 2 before volume 1!

(click on the cover page to go to lulu and buy!)

US $5.95 or £4.24 or €4.61 (PDF e-book)

(payable by PayPal or credit card)

Enjoy!

As you all may have noticed, I’ve finally started posting Hidoku puzzles on a daily basis!

They can be found every day, Monday to Friday, on the Hidoku page!

I hope you all had a nice Christmas and that you are enduring the cold weather well. Well, those in the Northern hemisphere anyway.

Let me tell you about the changes that I plan for 2009:

The two recently published books are now also available on Amazon:

Again, I would GREATLY appreciate if you rate and/or review my books that you purchase on Amazon, no matter if your review is positive or negative. It means a lot.

Here is something to keep you amused during the coming holiday season…

The book contains 150 puzzles ranging in sizes from 6×6 to a massive 15×15.

And folks, these puzzles aren’t easy, I can tell you that. You will even find 9 INSANE puzzles! I’m just a little worried that I’ve overdone with the difficulty, but we’ll see how you feel.

Enjoy!

Here is an explanation of a Hidato solving technique that some people might find obvious and they use it without even thinking of it as a special technique. But, for those who still struggle with the more difficult puzzles, here is a quick guide of the technique that I call “cornering“.

It can be used when a cell has only one “neighbor” that is an empty cell. In such a case, that cell (with only one empty neighbor), must contain a number that is consecutive to (at least) one of the already filled in neighbors.

Look at the upper left corner. Number 33 could in theory go into any of the 4 cells that are neighbors to both 32 and 34. However, it must actually go into R1C1 (row 1, column 1). Why? Because R1C1 has only one empty neighbor and according to the rule I stated above, in such a case that cell must be consecutive to (at least) one of the existing neighbors.
Why? Because each cell (other than 1 and the largest number) must have both a “+1” and a “-1” neighbor. So, the only options for R1C1 are 31 or 33 or 35. If you put any number other than one of those in R1C1, it would have only one of the “+1”, “-1” neighbors, because there is only room for one number next to it. That is why I also call this technique “dead-end”. But 31 would be too far from 29; and 35 would be too far from 39. Therefore R1C1=33!

Now, look at R1C7 (it’s circled). See if you can figure out why the number in that cell MUST BE 5.

I believe that after all the puzzles that I’ve created and posted for you, you know that I prefer them difficult.

It seems that there is a belief that the difficulty of Hidoku can only be increased by increasing it’s size. I know for a fact that it’s not true, because some of the Hidoku puzzles that I’ve created are really fiendish.

Anyway, today’s puzzle is a small-but-not-too-easy one. I’d like to hear from you how you rate it’s difficulty.

6×6 Hidoku for Friday, October 31, 2008.

Click to download the puzzle in your favorite format:

png solution – final

Enjoy!