Friday, 4 May 2012

Friday Puzzles #155

So I thought what I'd do for a while before sharing my puzzles this week is bore you a little with some copyright.  The puzzles on this blog are free for anyone to use and reproduce under the following conditions.  The first condition is that you do not use them for commercial purposes.  If you want to make my money from my puzzles then it is unacceptable that you do so without a (large) cut coming my way.  The second is that I am fully attributed, so that my work is fairly recognised as belonging to me.  This should at the very least feature my name and a link to this blog.  Should you wish to use my puzzles under any other terms, then you should get in touch and we can talk.

This is as stuffy as I am going to get with my puzzles.  I maintain this blog for the benefit of the community.  I would like the community to grow and expand, and if my puzzles can be used as part of this, then this makes me very happy indeed.  Although it would be nice, should you wish to use my puzzles elsewhere, to ask me first, I do not deem this to be necessary.  As long as you aren't being overtly offensive or abusive when using my work I will in fact be glad of the good advert whether I am conscious of this advert or not.

I wish more people shared my attitude.  With the advent of the internet, I believe a revolution in copyright is coming.

Anyhow, this week I have two Sudoku variants that I put together for the Polish national championships, which recently happened.  Two puzzles which I'd have been more than happy to have been published elsewhere, under the conditions outlined above, so that the wider community could enjoy them.  Turns out they are here first instead.  Enjoy!
    #186 Arrow Sudoku – rated hard
    #187 Irregular Sudoku – rated hard
All puzzles © Tom Collyer 2009-12.


  1. Very nice puzzles! I actually participated in the event and loved the puzzles this year, didn't know you were one of the authors.

  2. Ah - well I think it's generally a good idea for competition puzzles not to advertise who is responsible for which puzzle until after the event. For better or for worse, individual authors have their own signature style which is inherent to the puzzles they create and this can often be an advantage if the solver knows what to expect beforehand.

    Obviously you might be able to guess at the author - for instance I don't think I've seen anyone else do the whole multi-arrow thing and so I think people who have seen my other puzzle like that might have reasonably guessed I was behind that puzzle - but I think it's fairer if the solver doesn't know that.

  3. Really good puzzles, Tom.
    I had great difficulty to start the arrow, found it quite hard !
    The irregular is much easier, even if you know that I could have seen this particular design somewhere...

    About multi-arrow: that's true that it's rare, I've seen yours last year at the ukpa tournament, I think. Bastien made another one last year for the french prequalification:
    I did another one for a turkish publication last year (so you'll not find it on internet).


    P.S.: you can find other puzzles that appeared on the polish championship on my blog:

  4. Fred, I saw your puzzles for Poland on your blog and it reminded me that I could have a relatively easy week for my blog. :) The arrows, like my UKPA one, has some really interesting combinatorial logic. I especially like how box/column/row constraints deeply affect the make up of each of the arrows. You can't consider any particular arrow in isolation, you have to consider all of them together!

    Anyway thanks for your kind comments. I hope to find enough spare time at some point to have a go at the many great puzzles you have been posting recently :)

  5. I solved the irregular, but I'm having a lot of trouble with the arrow. I have eliminated every possibility for R7C7, so there's something wrong somewhere.

    Is the grid transcribed right?
    Is the number in a circle equal to the sum of the numbers along any attached arrow?

  6. I've not resolved it for a while, but it's exactly the same file as I sent to the Polish organisers so it'll have been through more than the usual layers of checking... to put it another way I'm much more confident of these puzzles being right that normal :p

    I would say you might be having trouble with digits repeating on arrows but that doesn't apply for this puzzle. If it's of any use, I'm struggling to see how you managed to eliminate 5 from that cell ;)

  7. Still don't have it. Do the five circles hold, from top to bottom, 7 6 9 8 5?

  8. I'm running into a contradiction with the arrow sudoku, too. I get the same circles as cyrebjr, and then run into a contradiction placing the 3 in the top middle square (there's a 3 center of bottom row).

  9. Just plugged the confirmed information into a solver. It can't handle arrows, so I've been working that "manually," as it were. After handling the four central arrows, I've narrowed the difficulties to this:

    -Upon adding just the arrows pointing to R1C5, that cell can only contain 1.
    -Upon adding just the arrows pointing to R9C5, that cell can contain only 3.
    -Upon adding both above pairs of arrows, there is no solution.

  10. I've just had a closer look at my notebook. The solution I've got pencilled in is broken in exactly the ways you've highlighted - there are two 8's in C4 and two 3's in C5. I'm not sure what to say - that particular red herring has masqueraded itself past lots and lots of people.

    Interestingly, the givens don't seem to match the initial solution grid (which is valid) that I've got pencilled in. I'm going to see if I can belatedly rescue this one...


Contact Form


Email *

Message *