159²
(Published on 28. February 2023, 23:07 by Arlo Lipof)
Rules:
- Normal Sudoku rules apply.
- 159² Rule. Digits in columns 1, 5 and 9 index the column locations of digits 1, 5 and 9 respectively, in each row; similarly, digits in rows 1, 5 and 9 index the row locations of digits 1, 5 and 9 respectively, in each column. E.g. if digit (3,1) is a 7, then digit (3,7) is a 1; similarly, if digit (5,8) is a 2, then digit (2,8) is a 5.
- Rotational symmetry. Digits in cells (R,C) and (10-R,10-C) always sum to 10.
Links: F-Puzzles, F-Puzzles (white), CTC, CTC (white)
Enjoy! Ratings and comments are welcome of course.
Solution code: Row 2 then Column 3 (18-digit number without spaces)
Comments
on 12. February 2024, 22:09 by ViKingPrime
Good stuff! Thank you for the recommendation, very satisfying to solve.
on 11. September 2023, 23:03 by MarthaB
This is a great indexing puzzle. I can't understand why the rating is low.
A: Thank you, me neither! ;-)
on 29. March 2023, 04:33 by Colonel
I put in a solution code that worked but it said it was wrong. Is there instruction on rotational symmetry? The explanation was not clear.
A: Yes, in the final grid the digits in ‘opposite’ cells (R,C) and (10-R,10-C) always sum to 10, e.g. in cells (4,2) and (6,8) the digits 1 and 9 sum to 10. (Sorry, I didn’t see your comment earlier.)
on 6. March 2023, 01:05 by josemadre
Great construction, difficulty 2 stars for me
A: Glad you liked it!
on 4. March 2023, 18:49 by Danekiller
A very nice idea and the Logical Path is very nice as well. Agree however With earlier speaker that this should rather be considered 3 in difficulty thank 2
A: Thank you for your nice words! I had set a 3* difficulty at first, but decided to change it for 2* in the end because there have been a lot of indexing puzzles posted recently here on LMG, and so imo a lot of solvers are quite experienced in solving them.
on 2. March 2023, 20:42 by Shrouded
The double 159 rule is always tricky to follow in your mind, but the combination with the rotational symmetry works well and makes for a fun challenge. Definitely closer to 3 stars difficulty imo
A: Thank you for your comment. In my opinion the difficulty of this puzzle really depends on your previous experience with the typical 159 logic.
on 1. March 2023, 03:34 by Puzzlers100
There is only one correct answer, make sure to double check the radial symmetry rule when solving for the last bit of the puzzle!
