Hydra
(Published on 12. May 2021, 18:33 by zetamath)
Normal irregular sudoku rules apply, but the regions must be determined by the solver. That is to say, every row and column must contain the digits 1-9 exactly once, and there are nine orthogonally connected regions in the grid that also contain the digits 1-9.
Each region takes the form of a friendly serpent, which is one cell wide, 9 cells long, and does not touch itself, even diagonally. Each serpent has a head and tail, also to be determined by the solver.
We think of the head of the snake as the first cell, the next cell as the second, and so on. A cell in the grid is circled if the digit it contains matches its position in this way. That is, the head is circled if it is a 1, and the tail is circled if it is a 9, and so on.
ALL circles have been given.
Have fun, leave a comment if you enjoy the puzzle!
Solution code: Row 8
Comments
on 14. February 2023, 17:03 by codewizard
For those who prefer CTC/SudokuPad: https://app.crackingthecryptic.com/sudoku/btgQm83JD2
on 13. January 2023, 20:46 by StephenR
Most enjoyable, thanks. Would be happy to see more like this.
on 14. April 2022, 20:03 by Christounet
Digging up some of your "old" puzzles. This one was quite approchable and still very fun! And it does look like an Hydra when completed, which is a nice reward for the solver !
on 3. June 2021, 12:14 by Vebby
Very enjoyable! :)
on 24. May 2021, 21:56 by Klausku
I really enjoyed this one. Challenging but not too difficult. Really nice how the deadly pattern cleared itself at the end. Thank you very much.
on 23. May 2021, 17:09 by Klausku
I really enjoyed this one. Challenging but not too difficult. Really nice how the deadly pattern cleared itself at the end. Thank you very much.
on 23. May 2021, 15:08 by Mody
Großartig
on 23. May 2021, 08:29 by Klausku
I really enjoyed this one. Challenging but not too difficult. Really nice how the deadly pattern cleared itself at the end. Thank you very much.
on 14. May 2021, 00:35 by MagnusJosefsson
Very nice and enjoyable solve!
on 13. May 2021, 23:30 by SenatorGronk
Thanks, this one was fun!
on 13. May 2021, 21:25 by Klausku
I really enjoyed this one. Challenging but not too difficult. Really nice how the deadly pattern cleared itself at the end. Thank you very much.
on 13. May 2021, 17:07 by henrypijames
Incredibly intricate, just wow!
Don't remember using the "no diagonal touching" rule - is it really necessary?
Suggestion for Penpa+: Use the dotted circles, which are transparent and allow for coloring of the cells.
[It is not necessary, and indeed I think you could prove it can't happen because it would lock off too few cells to fit another snake. However, I figured it was better to include what I consider "standard snake rules" to make it easier to parse, but I'm never quite sure with things like this!]
You're right of course. In fact, the no-touch rule can be dropped entirely, stating instead that being one-cell wide means a snake cannot occupy any 2×2 block of cells.
