Double Indexing Miracle
(Published on 29. June 2024, 10:15 by egubachu)
The puzzle
Rules
Normal sudoku rules apply: Place the digits 1 to 9 once each in every row, column, and box.
- Antiknight: Cells that are a chess knight's move apart cannot contain the same digit.
- Column indexers: Every cell in the grid is a column indexer. This means that if the digit in cell (R,C) is D, then the digit in cell (R,D) is C.
- Row indexers in columns 1, 5, and 9: Every cell in columns 1, 5, and 9 is a row indexer. This means that if the digit in (R,C) is D, then the digit in cell (D,C) is R.
- There is at least one cell (R,C) in the grid with digit D, for which R=C=D.
Play online
Solution code: Row 5
Comments
on 10. July 2024, 08:34 by virus_dave
Oh my goodness, what an amazing puzzle. Took awhile to find the key insight, but once I did, everything else flowed so very naturally.
Unlike many other puzzles, i can't imagine how one would solve this WITHOUT that insight.
I'm seriously impressed that this solved at all.
~~~
Thank you so much for your wonderful comment virus_dave! I'm so glad that you managed to break in this puzzle. The break-in feels almost like a theorem to me, and when I had this idea I felt extremely lucky to find that with only one extra rule (the R=C=D rule) the grid has a unique solution, and actually has a nice solve path. But it's not an easy puzzle, so a big congratulations for solving it!
on 30. June 2024, 09:55 by yanggang
Very tricky, a beautiful solve. I can't believe this ruleset works so well!
