Thursday 5 November 2020

Puzzle 352 Sudoku

So here's a puzzle with an idea on a recent theme.  I'd say the execution is reasonably good, but as I'm working mostly by hand it doesn't quite feel polished to its true potential.  It's still doable if you don't get the idea, but fair warning, it might be a bit of a slog.  Failing that it's probably very guessable.  But I have more faith in you than that, dearest reader.  Enjoy!
   #352 Sudoku – rated 8/10 [Very Hard]

Update: I might downgrade this from a 9 to an 8 as I've just realised the intended pattern used is very similar to the original Phistomefel pattern, which perhaps is a bit easier to spot and make use of...

All puzzles © Tom Collyer 2009-20.


  1. Nice puzzle, Tom. I did use Phistomefel, curious to see what your intended path is.

    You might also be interested in this puzzle, which I posted yesterday:

  2. Hi Philip,

    These comments are rubbish (I'd post an image if I could) - but if you go to the google sheet I set up and set

    Rows 3,7 as -1 and Row 5 as +1
    Columns 3,7 as -1 and Column 5 as +1
    Boxes 1,3,7,9 all as +1 and Box 5 as -1

    The you end up with a nice tartan style pattern, similar to Phistomefel but not quite - in particular there's an extra 1-9 set to take account of, which in this case I filled with givens. There might be nicer ways of executing the idea so that it doesn't quite as easily reduce to a "standard" Phistomefel (I say, standard, but it really hasn't been that long since accidentally finding on LMD what was the first non-trivial example to me)

    1. That same pattern can be viewed as a normal Fred partition, which is how I solved it.

    2. Yeah you're right Sam - it is equivalent to one of Fred's 5/4 partitions.

      Equivalently you can set:
      Rows 1,2,5,8,9 to +1
      Columns 3,4,6,7 to -1

      And you get the same pattern


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