Friday 10 June 2011

Friday Puzzles #108

So in the midst of my triple posting last week, I managed to put out a completely broken Sudoku puzzle, where I’d presumably mistyped one of the digits. Looking back a bit later, I realised it was broken but couldn’t find the dodgy digit, so I went back and changed it.

Anyway, more Sudoku today. This weekend is the UKPA’s Sudoku championship – and I have taken the liberty to put together an example of one of the featured Sudoku variants.

Incidentally, if you want to participate, UK citizen or otherwise, then you should definitely read the instruction booklet and the discussion thread. To actually take part in the test, you will have to be a registered member of the the UKPA forums. Registration is free and easy!

Anyhow, back to the variant. This one has the rather inelegant name of “No Donkey Step Sudoku” – perhaps when I have a free moment (haha) I’ll try and think of something better. Anyhow, the idea is fairly simple. Classic Sudoku rules as you know and love them, with the additional constraint that digits may not repeat within 2 cells on a diagonal line at 45 degrees. If you are familiar with no-touch sudoku, then this is simply a slight extension of the constraint. If you still don’t get it, have a look at my good friend Rishi Puri’s example, which has the advantage of coming with a solution grid. Enjoy!
    #136 No Donkey Step Sudoku – rated medium 
All puzzles © Tom Collyer 2009-11


  1. Well, the name was originally intended as a joke, and the rule was written in a fun way, explaining that a donkey is somewhat moody ; so, he sometimes walks this way (1 cell in a direction, then 1 cell orthogonally), and sometimes that way (2 cells in a direction, then 2 cells orthogonally). I didn’t expect other authors to seize the idea and create some other puzzles of this same type. Which is great, but these authors didn’t keep the fun part, and so I understand that the puzzle’s name does appear a bit strange now. Still, I am really pleased that this variant has some fans – and by the way, I am gonna copy out this puzzle and try it right now.


  2. Done. I found it very easy (the puzzle can nearly be solved by using only the untouch rule), but nice. Certainly better than my first attempt of this variant.


  3. It’s true, there are 23 givens and that probably seems like a lot in retrospect. I think I posted medium because I linked to this from the UK forums, and this isn’t really a variant that many people doing the championship this weekend will likely have come across.

    Actually the pattern of givens is quite interesting. I wonder if I can manage to get a classic puzzle to work with them…


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