Four Colour Theorem
(Published on 19. March 2022, 13:12 by Jay Dyer)
Rules
- Each row, column, and 9-cell region must contain the digits 1-9 once each. The regions must be determined by the solver.
- Each region must be colored in its entirety with a single color. No two regions of the same color may share an edge, and at most four distinct colors may be used.
- Cells containing arrows give the distance to the nearest cell of the same color in each indicated direction (neighboring cells are a distance 1 from each other). All possible arrows are given.
Solve in Penpa+ (Answer check is on digits and edges).
Solution code: Columns 1 and 9
Comments
on 25. July 2025, 02:15 by Nell Gwyn
I also had a much harder time after the regions were drawn than drawing them. Still a fun puzzle though!
on 14. April 2025, 20:50 by adelaide
beautiful puzzle !
on 3. March 2025, 15:20 by StephenR
Super stuff, thanks. I may have missed some things, but the irregular sudoku at the end seemed very hard.
on 13. July 2023, 08:23 by tesseralis
this has been on my bucket list for months and I'm happy I've gotten to finally do it!
on 3. June 2023, 16:53 by Flambierter Flamingo
Holy shit, I can't believe I solved this! My first five star, thak you!
on 17. October 2022, 13:04 by Vebby
Brilliant puzzle, a joy to solve!
on 16. September 2022, 23:29 by SHERAX
Another Genius Puzzle From One Of The BestConstructors.
An other masterpiece from him : Roman Lockout
(Only 5 times solved)(overlooked by almost everyone)
on 12. September 2022, 21:20 by derKrampus
The logic flowed very smoothly, after completing the regions I missed something for a long time so completing the irregular sudoku took me almost as much as building the regions did
on 12. September 2022, 03:18 by SimplePurpleFrog
Wow, really hard, but amazingly beautiful. It even flowed logically, though at a trickle :-)
on 12. July 2022, 00:48 by TotallyNormalCat
Definitely one of my favorite chaos constructions
on 11. July 2022, 19:16 by Niverio
Wonderful! Region building part was full of nice surprises :)
on 4. May 2022, 02:12 by OGRussHood
The rules were really wonky. Took me a half-hour just to latch on to them. Then I could actually do the puzzle. A brilliant work.
on 23. March 2022, 21:04 by 10feet
Wow, thank you!
on 23. March 2022, 19:42 by Krokant
A true marvel. One of my favorite sudokus so far. :)
on 22. March 2022, 21:49 by marcmees
amazing puzzle. thanks.
on 21. March 2022, 17:23 by SudokuExplorer
Discovering the regions was very enjoyable, thanks! :-)
on 20. March 2022, 19:16 by DiMono
Tricky and satisfying. Thanks!
on 19. March 2022, 18:17 by twobear
Great puzzle. Thank you!
on 19. March 2022, 17:16 by Jesper
Very nice, thanks!
on 19. March 2022, 15:24 by kolot
Wonderful, wonderful, wonderful!
One of the best puzzles of all time!
on 19. March 2022, 14:11 by Jay Dyer
Added some clarification to the rules about neighboring cells.
on 19. March 2022, 13:46 by twobear
Could you clarify on the last rule? Do neighboring cells count as distance zero or distance one? Thank you!
Neighboring cells are distance 1.
