Obvious Killer
(Published on 29. March 2021, 11:31 by filuta)
-a cage is an orthogonally connected region without repeats,
-a cage of size N is called obvious, if it sums to a number that can be expressed in only one way using N numbers 1-9 without repeats.
Rules of the puzzle:
Standard sudoku rules apply.
In addition, all possible 2,3 or 4-cell obvious cages that can be drawn in the finished solution are given as clues (i.e. there is a negative constraint on obvious cages) in the following sense:
Every obvious cage of size 2, 3 or 4 that appears in the finished solution is either:
1) drawn in the grid (drawn clue), or
2) represented by its total written by a small number in the upper left corner of one of its cells (total clue).
The cages may intersect.
Each total clue represents exactly one obvious cage (i.e. two overlapping cages of same total cannot be represented just by one total clue in one of their common cells).
Each cage is represented by exactly one clue.
(so for instance, in the finished solution of this particular puzzle, there are exactly 7 obvious cages of size 2, 3 or 4, three are indicated by a drawn clue and the remaining four by a total clue).
Have fun!
f-puzzles link
Solution code: column 5 and row 6 (without a comma or a space)
Comments
on 14. August 2024, 13:55 by Silverstep
What a satisfying finish to this whole journey! Very impressive to set a grid like this, in the days before computer solvers.
on 25. June 2024, 23:28 by Styku
This was way too hard for me. Had no idea where to look. Took me half a day to finish it. Trully a monster! I have no idea how you managed to create it. I salute you!
on 20. May 2024, 10:52 by The Book Wyrm
Very impressive puzzle. Amazed that it's possible to get a unique grid with so few clues, especially one with an interesting solve path like this.
Some pretty interesting logic in this, especially the break-in.
on 1. March 2024, 22:36 by Sapio
I think this was my very first very hard puzzle, only because I was trying to solve all the wrogn puzzles and I came across your second puzzle. This was a monster of a puzzle but I'm so glad to have slain it. The break-in was a thing of absolute beauty and the negative constraint carried all the way to the very end. It took me two tries and a combined ~4 hours of effort, but my goodness was it that much rewarding. Thank you so so much!
on 3. December 2023, 10:30 by Yann
A masterpiece, with a negative constraint that keeps on giving, including in that magical ending, thank you for your efforts to set this !
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thank you so much, Yann!
on 24. November 2023, 14:54 by wullemuus
So sparse "obvious" clues are enough- incredible! Juggling with the negative constraints made my head spinning and it needed some time to not miss any ... . The rest was easier than expected (due to the brilliant logical structure). Pure pleasure!
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thanks a lot! I also just posted a link to a solve video I made a while ago, in case you are interested
on 22. August 2022, 17:06 by polar
A very original ruleset combined with flawless execution. Loved it! Setting this must have been quite the task.. Thank you for your efforts! Glad to see a rating has now popped up too :)
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yeah, quite cool this one is getting all the solves lately, after all that time, and indeed, I must say no other puzzle took me probably even half of the time as this one, but it was totally worth it. I'm so happy you liked it too and thanks for your kind comment!
on 28. July 2022, 04:26 by Samish
Few puzzles deserve the title of miracle sudoku more than this one. His existence is an utter satisfaction. Bravo !
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Thank you so much!
on 16. July 2022, 18:34 by Steven R
Absolutely magnificent, one of the best puzzles I've completed.
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wow, thank you, I'm so happy you liked it so much!
on 1. July 2022, 22:00 by filuta
changed difficulty
on 1. July 2022, 10:04 by Vebby
Very interesting logic! 5/5 difficulty for me.
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And thank you once again. And yeah, I think it is finally the time to raise it to 5 stars.
on 3. April 2022, 10:29 by Phistomefel
The break-in was just a magical piece of logic. After that, I had some problems finding the right spot to look for the very powerful, albeit subtle negative constraint. After finally discovering the right spots, I found some beautiful deductions there though. Thank you very much for setting this beauty, filuta!
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And I thank you for such kind words, your comment really made my day.
on 12. March 2022, 02:08 by Piatato
Wow!!! What a masterpiece! I literally had tears in my eyes toward the end of this solve. The utter brilliance of this construction cannot be justifiably described by my words. This has to be solved to be believed!
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oh, wow, thank you so much, that really means a lot to me.
on 3. September 2021, 00:12 by SudokuExplorer
Both puzzles were a lot of fun to solve! This one in particular was very elegant and the use of the negative constraint lead to many "aha" moments. Thanks! :-)
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thanks a lot, yeah, I always thought of this puzzle as kind of epitome of negative constraint in a way
on 19. August 2021, 10:09 by Prutsbeest
To be honest, I have used bifurcation on two occasions: at the very beginning to determine which one of two paths I should use, and somewhere towards the end of the puzzle as well. But once I had started the puzzle, the logic flowed very nicely for me and it was not all too difficult anymore.
The mere fact that this puzzle has a unique solution is just mindblowing. Amazing construction indeed! Thank you!
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oh, thank you so much (once) again for both the solve and the kind comment
on 1. July 2021, 06:11 by Kafkapharnaum
FINALLY, I did it. My goodness, this one is mean, first I just assumed that the numbered clues had to be in the left topmost cells of a given cage (my mistake though, it does say "*one of the cells* in the rules), and then, just one mistake in repeatedly misplacing a particular digit led me to fill (almost) entire grids that couldn't be completed...
But yeah, in the end, none of that can prevent me from seeing that this is a masterpiece of a construction -- the finish to complete the grid, I mean, I have no words...
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oh, wow, what a dedication, thank you so much for not giving it up! and also thanks for the comments. I must confess, this is the only of my puzzles where I knew from the beginning it's gonna be hard (and you know that means something). But really, I'm so happy you finally did it, I actually had another try on your Seer puzzle two days ago and wasn't so successful, so at least one of us made it.
on 1. May 2021, 22:45 by Tilberg
Another great puzzle. So beautiful in its minimalistic form and original, elegant ruleset. An absolute joy!
filuta: Glad you liked it. Thanks a lot!
on 30. March 2021, 22:22 by Gramor
First I could not believe that the given information is enough to solve this, but here we are :)
Beautiful logic from start to finish, thank you very much for this puzzle.
filuta: I am glad you liked it and thank you very much for such a comment (and for the solve as well, I must say, I was almost prepared to change it to a (less elegant) version with more clues, after it was getting no solves).
on 29. March 2021, 11:58 by filuta
labels changed
on 29. March 2021, 11:38 by filuta
Fixed the f-puzzles link.
