What an Odd Sight (Parity Sight Lines)
(Published on 17. February 2025, 22:48 by damo_89)
Setting with a new constraint to me, parity sight lines. Consensus testing estimate was 2 stars for difficulty, and please be aware of the negative constraint. Good luck!
- Normal sudoku rules apply: Place the digits 1 to 9 once each in every row, column and 3x3 box
- Parity Sight Lines: (see below for an example)
- A digit in a circle is odd and counts the number of odd digits that can be seen in all orthogonal directions combined, including itself. Even digits block the view
- A digit in a square is even and counts the number of even digits that can be seen in all orthogonal directions combined, including itself. Odd digits block the view
- ALL circles and squares are given
If you are not familiar with sight lines, hopefully this image helps explain:
- The 5 in the circle sees itself, 7 in its row, 9 in its column, and the pair of 1s in its row and column. It does not see any of the 3s as the 3s are either blocked by even digits, or not in the same row/column as the 5
- The 4 in the square sees itself, a 2 and two 6s
- The 1 in the circle sees no other odd digits as the even digits block view, so it only sees itself
Solution code: Row 9
Comments
on 21. February 2025, 07:27 by shartus
Wow what a puzzle -- one where I'm sure the early going is similar for everyone, but you feel like you're finding a unique path :)
on 19. February 2025, 23:50 by TheKyoshiroFan
I love how "ALL circles and squares are given" is used at some point in the solve. Well done!
on 19. February 2025, 21:08 by jubengo
Lovely puzzle :)
on 19. February 2025, 03:39 by e_reads
The break in was so fun on this one. I got tripped up because I forgot the negative constraint!
on 19. February 2025, 00:26 by Snaques
What a puzzle!
This was one of those that looked just impossible, but once you just started working on it it was suddenly just done. In the end 2* was pretty spot on.
GJ Demo!
on 18. February 2025, 17:32 by Franjo
Wonderful and approachable puzzle. When I found the break-in (that took some time) it was a very smooth solve. Thank you very much for creating and sharing this lovely gem.
on 18. February 2025, 15:26 by Snookerfan
Very nice puzzle! I am glad this one gets the rating it deserves as opposed to your previous puzzle. Thank you
on 18. February 2025, 13:55 by Flinty
Lovely stuff.
on 18. February 2025, 12:26 by ImperfectRainn
Wonderful puzzle, I very much enjoyed this ruleset and it flowed fantastically. Looking forward to more of these!
on 18. February 2025, 11:32 by Fizz
Very fun puzzle with carefully placed hints throughout. Thanks!
on 18. February 2025, 11:20 by jcgodart
Very nice. Note to myself : remeber the rules till the end ! I forgot the negative constraint but could solve most of it, nevetheless. FWIW, placing a circle in r8c3 would turn it into puzzle with a unique (different) solution, not requiring a negative constraint.
on 18. February 2025, 10:26 by 9Rookienumbers
Lovely puzzle. A perfect 2* puzzle: I found the break-in after quite some time, but after that it flew really nicely
on 18. February 2025, 03:45 by gdc
Didn't look like a 2* ruleset at first but really smooth and approachable execution. Thanks for a fun puzzle!
on 18. February 2025, 02:05 by mathpesto
Had a lot of fun with this one, and was surprisingly approachable!
on 17. February 2025, 22:50 by damo_89
Although this constraint was new to me, I imagine it has been used before - would love to see previous puzzles using this constraint if anyone can point me towards them.
