November 04, 2011

Friday Puzzles #129

So this is my last entry before I jet off to Hungary to have a shot at firstly the World Sudoku Championship, and then the World Puzzle Championship next week. I’ll be travelling with laptop and notebook so there might even be a puzzle next week. I invite you, dearest of readers, to be on the lookout for updates here throughout the week.

For those that are interested, the instruction booklets for each competition are filled with some intriguing ideas.

This week’s puzzle has been taken from the WSC booklet. The only previous examples of these that I’ve seen have been no larger than 7×7 grids, but I’ve whacked this up to full size. The rules are as follows: 1-9 exactly once in each row, column and marked region. Some squares are split in half; exactly one half is to be filled, the other to be left empty. You have to determine which. I’m not totally convinced this is genuinely a hard, but I’ll give it that label anyway what with the novelty value. Enjoy!

#159 Halved Squares Sudoku – rated hard

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All puzzles © Tom Collyer 2009-11

- 8 comments by 1 or more people Not publicly viewable

[Skip to the latest comment]
  1. David C

    Errrr, column 3 ?!

    04 Nov 2011, 21:41

  2. whoops, that 1 should be a 5, let me fix it…

    04 Nov 2011, 21:45

  3. Fred76

    Made me feel crazy !!!

    At the 5th tentative, it was correct !

    Thanks for the grid.


    05 Nov 2011, 18:47

  4. The idea Fred was to try and put something more horrible than will appear in Eger. Hopefully this will prove to be the case!

    05 Nov 2011, 21:26

  5. Fred76

    Agree !

    Your grid let me see some interesting things, especially concerning uniqueness technique. You can apply uniqueness technique to a single digit !
    For example, in your grid, R6C3 and R5C4 can’t contain the same digit.

    05 Nov 2011, 22:01

  6. Yeah, it’s an interesting observation. Initially I had wanted to put no givens in the halved cells – if nothing else the formatting looks a bit rubbish – but I couldn’t get anything unique out. Perhaps this is a limitation to the variant in larger sizes, but I’m not totally convinced we’ll see many in a 9×9 size anyway…

    05 Nov 2011, 22:50

  7. Bryce Herdt

    Good workout.

    Have you seen any similar puzzles with all regions convex? I’ve made a 7×7 grid with that property, but I haven’t figured out how to fill it.

    07 Nov 2011, 18:01

  8. Fred76

    Puzzles of that round were really nice !!!

    It seems like I had mental “blocages” on these puzzles, and if you add (or more precisely if you subtract) 40 points lost for a single empty cell, it was one of my really bad round of this WSC.

    10 Nov 2011, 22:58

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Welcome to the blog of current UKPA sudoku champion, two-time Times national sudoku champion and general logic puzzle fan Tom Collyer.

Home of the original Friday Puzzles, each Friday I publish a 100% original and handmade logic puzzle, inspired by the world-famous Nikoli company.

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Latest comments

  • I like the appearance of the solution. :P Nice one. by Prasanna Seshadri on this entry
  • I think I've seen something vaguely similar in some of Palmer's puzzles as well. To be honest I've a… by on this entry
  • That's two puzzles in a row where I find something I had used before. I know, not plagiarism; just g… by Bram on this entry
  • Kota, that's not really true. I had made my puzzle before going to the WPC already. Also I don't hav… by Bram on this entry
  • About 20 minutes, after restarting from a mistaken conclusion. by Bryce Herdt on this entry

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