1919 Sandwiches
(Published on 21. January 2023, 04:04 by RockyRoer)
This is the latest in my "Sandwiches Without Givens" series. Other puzzles in the series are:
- Pentomino Sandwiches
- Tetromino Sandwiches
- Double Decker Sandwiches
- What Do Little Killers Eat?
- What Do Killers Eat?
- Crusties - a sandwich experience
- Numbered Sandwich Counts
- Full Rank Sandwiches
- Boxed Sandwiches
- Product Killer
- Regional Sums Sandwich
- Sandwich Sweeper
- VXL Sandwiches
- Diagonally Cut Sandwich
- Ren Ban Sandwich
- Sandwich Capsules
- Palindrome Sandwiches
- Clue Sandwich
- 159 Sandwichs
- Friendly Sandwiches
- XV Sandwiches
The Rules:
- Normal sudoku rules apply.
- [19 Indexing Rows/Columns]
- Digits in row 1 indicate which row contain the 1 in each column.
- Digits in row 9 indicate which row contains the 9 in each column.
- Digits in column 1 indicate which column contains the 1 in each row.
- Digits in column 9 indicate which column contains the 9 in each row.
- [Sandwich] Clues outside the grid indicate the sum, or parity of the sum, of the digits sandwiched between the 1 and 9 in their rows/columns.
The Puzzle:
CTC: Click here
Solution code: Row 5 and column 5
Comments
on 2. February 2023, 03:02 by SimplePurpleFrog
I loved it, stunning piece of logic. Fantastic break-in :-)
on 22. January 2023, 12:52 by argl
Dumb question, if say r1c7 is a 9, would r1c9 be 3 or 7? How does the indexing work?
Reply: That's not a dumb question at all, but actually quite important to the solve path of this puzzle.
If r1c7 is 9, then r1c9 must be a 7 because the 9 in row 1 is in column 7. In that scenario, the 1 in column 7 has to be in R9c7, and the 1 in column 9 has to be in R9c9 because of the 7 and 9 in row 1. That actually places two ones in box 9, and would break the puzzle. So in fact, r1c7 cannot be 9. These sort of little mini-chains of logic are present in many places in indexing puzzles, and help explain why this puzzle can be solveable with just two number clues and a handful of odd/evens...
Hope that helps! Good luck!
on 22. January 2023, 01:20 by Samish
Very nice! Taking a step back, only two given values along with a few parity clues is pretty impressive to make such a nicely solvable puzzle.
on 21. January 2023, 17:23 by marcmees
nice ... again. Getting spoiled. thanks.
on 21. January 2023, 17:04 by SenatorGronk
As with so many Rocky puzzles, even after grokking the central conceit, I remain stunned how smoothly it solves with so few additional clues.
on 21. January 2023, 08:53 by Elliott810
Brilliant puzzle with a fascinating break-in! Thanks:)
on 21. January 2023, 05:48 by glum_hippo
This was delightful
