DJ Ape .Net – The Home of Perfect Sudoku

This is to let you know that I’m taking a long weekend, so there won’t be any puzzles posted on Friday, April 28.

To keep you happy , today’s killer sudoku is rated IQ/INSANE, so it should give you a good challenge.

I also posted my first ever “non-consecutive” Sudoku on the “Daily Sudoku” page. When you look at it, you might first think “This isn’t possible, it’s a Sudoku with only 11 clues”. And we all know at least 17 givens are needed for a valid Sudoku. Well, that’s true, but this puzzle has an additional restriction: you can’t place two consecutive numbers next to each other!

By the way, the rumour has it that there are a few brand new puzzles posted today on that “other site”.

See you all early next week!

Yet another Sudoku puzzle variation – it’s somewhat similar to “greater/less than” puzzles but completely new solving methods are required to solve it. It is called Consecutive Sudoku, although I’ve seen it under the name “Disallowed Number Place”.

You start with very few givens (in fact I have created these puzzles with only a single starting clue), but you also have marks between cells that contain consecutive numbers. These are marked with a thick pipe symbol | between cells.

Don’t think these are too easy. They can be made extremely difficult to solve!

Apart from the obvious methods for solving these (if you have solved a cell with number 1, and there is a | symbol, you know that adjacent cell must be 2), here are a few hints to help you out:
1. Use pencilmarks and apply “pipes” to them. If a cell, for one reason or another, can contain, for example, only 5 or 8, and there is a pipe, you know that the cell next to it can contain only 4 or 6 or 7 or 9.
2. Where there is no pipe – it’s also a clue! Don’t forget to use it! If you solved a cell with number 4 and there is no pipe, you know that the cell next to it can’t be neither 3 nor 5!

The second hint is very important. In fact it is possible to make puzzles with no consecutive numbers in it – so the puzzle looks like regular sudoku, but there are only, for example, 8 clues! If you didn’t know that puzzle was “consecutive” you would think it is impossible to solve. More about that when I construct and post one such puzzle.

Okey dokey, here is the puzzle: Consecutive Sudoku for Monday, April 24.

Download the puzzle by clicking on this thumbnail:

solution – final

It’s been a while since I last posted a Killer Samurai puzzle and it’s time to bring you another challenging puzzle with this layout.

Click on the Samurai thumbnail to download the puzzle.

The final solution is here.

This is just a reminder that from last week I started posting Weekly Sudoku Samurai X puzzles on the Samurai Sudoku page.

I just uploaded this week’s puzzle on the same page.

Since my Sudoku K book is still a few months away, it is time to introduce another book with my Killer Sudoku and Samurai Sudoku puzzles and puzzles from other puzzle creators.

The book I’m talking about is called “Teach Yourself: Advanced Sudoku and Kakuro” by Nick ‘Afka’ Thomas.

A few words about the author first: Nick came second in the first-ever Sudoku Championship in Britain about this time last year, so he knows how to solve them quickly. He teaches logic and maths and is releasing another book some time soon about teaching arithmetic using games and logic; Nick is also a published games inventor, writer and a professional actor…

The book covers standard Sudoku (there’s about 40 or so puzzles of these), 16x16s (2 puzzles), Samurai (2 puzzles), Kakuro (15 puzzles), Killer (15 puzzles) and how to do quicker and better arithmetic. The main point about the book is that it teaches how to do the advanced stuff, and how to do the more basic stuff faster! When I say ‘advanced’ I think it’s fair to say that this book goes further than any book in teaching the most advanced techniques that the internet-community has been coming up with (including some of Nick’s own things!). For example Unsolvable Rectangles, Loops and Puzzles; several variations of what he calls “Magnetism”, which is elsewhere called Colouring or Fishy Cycles, naturally Swordfish and X-wings, XY Chains, and all that sort of thing. Unlike other books which give a few handy tips and then unleash you on lots of puzzles Nick has tried to make teaching points and illustrate them with a puzzle, then make another point and practise on another puzzle and so forth, with a handful of puzzles to practise each chapter on. Explanations are focussed heavily on the logic, and explain why the techniques work rather than just state that they do.

Here is a quote from the author:

I hope people will understand it all – but it’s radically different from anything else on the market: it’s very much for people who want to be able to do the hard and fiendish ones (and the even harder ones on the internet) quickly and effectively.

What I can add about Killer Sudoku puzzles: the easiest puzzle in this book is rated “Thinker”. There are a couple of INSANEs too. Nick asked for most difficult puzzles and I made sure to deliver them as requested.

Here is another Sudoku overlapping puzzle variation. This one was suggested again by udosuk, just like the butterfly puzzles. If you have seen Sudoku puzzles with this layout before – please let me know!

There are 5 puzzles that heavily overlap each other – in fact the center (inner) grid is completely covered by the remaining 4. So be careful – all 5 grids must be solved according to the rules of Sudoku. This inner grid, albeit being blank, actually provides most clues! How come? Well, by extensive use of the Twin Nonets technique, you will see that all clues from outer grids are also clues for the center grid.

Warning: Be careful when using Twin Nonets. Make sure you know which pairs of nonets correspond to each other. Each nonet on the side, top and bottom edges corresponds to one nonet in the center grid, NOT to another nonet on the edge. I hope you see what I mean by this.

Udosuk also suggested the name (flower), which I accepted for the time being, but this layout really reminds me of a board game that I can’t exactly remember what it is, nor the name of it. If anyone else can see this resemblance and can remember the name of that board game – please share it with us.

Alright, after all this introduction, here is the puzzle: Flower Sudoku for Wednesday, April 12 – this is the only place you can find these kind of Sudoku puzzles!

Download the puzzle by clicking on this thumbnail:

solution – final

Samurai Sudoku X for Tuesday, April 11 – this is the only place you can find these kind of Sudoku puzzles!

From now on, WEEKLY Samurai puzzles will be shown on Samurai Sudoku page.

This week’s puzzle has been moved to that page already.

I think it’s cleaner this way and easier for you to find your favorite puzzles.

I promised something special with the Clueless concept before – and here it is: my first ever Clueless Killer Sudoku puzzle. Again, thanks to Ruud from www.sudocue.net for inventing the “clueless” concept.

There are 9 Sudoku puzzles with no overlapping regions! If you attempt to solve them individually – you won’t get far.

Here is where the “clueless” part comes in: in all of those 9 puzzles, the center nonet is just one cage. As you plug in your numbers, center nonets (shaded in grey) start filling up. The trick is that those 9 center nonets, put together, also constitute a valid Sudoku puzzle. So, when you run out of ideas, start working on the 10th puzzle and it will give you enough information to solve the whole lot. Those 10 puzzles together have, of course, a single solution.

Clueless Killer Sudoku for Monday, April 10 – this is the only place you can find these kind of Sudoku puzzles!

Download the puzzle by clicking on this thumbnail:

solution – final