Intro to Psycho Look-and-Say Killers
(Published on 5. January 2024, 05:24 by heliopolix )
Psycho Look-and-Say Killers are one of my favorite indexing constraints. They index digits across the grid in a unique way. I set this puzzle as a playable introduction to the constraint for a harder puzzle, but the intro puzzle stands on its own. I hope you enjoy it!
Rules:
- Normal Sudoku rules apply, along with Psycho Look-and-Say Killers.
- Sudoku: Place the digits 1-9 once each in every row, column, and 3x3 box.
- Psycho Look-and-Say Killers: Digits in pink cages may not repeat. Each digit in a cage indexes a cell in the grid. The cell is located in the *box* with the digit's number, in the *same position* within the box as the cell containing the digit. A digit may index its own cell. The cage clue should be read as a look-and-say clue that counts the number of times a digit appears in all the indexed cells.
- For example, if the clue was 28, then there would be exactly two 8's in the cells indexed by the digits in the cage.
Streamers have permission to use this puzzle.
Example:
- In the example image, there must be two 8’s in the cells indexed by the 28 cage in box 2.
- The digit 1 in that cage indexes to *box* 1, and then to the cell in the *same position* in that box as the digit 1 in its box (the top-middle cell).
- The digit 3 in that cage indexes to *box* 3, and then to the cell in the *same position* in that box as the digit 3 in its box (the middle-middle cell).
- Since there must be two 8's in the indexed cells, both indexed cells must contain an 8.
Solution code: Row 6
Comments
on 20. June 2024, 00:56 by timotab
I think my brain is broken. But thank you!
on 10. April 2024, 13:31 by The Book Wyrm
Neat puzzle! Definitely does a good job of teaching how the constraint works.
on 5. January 2024, 21:28 by abadx
Quite tricky to work with the negative constraint of psycho look-and-say. 3 stars for me but possibly because I'm not used to this constraint
on 5. January 2024, 19:30 by dumediat
This is the perfect introduction to psycho look-and-say! Thank you so much for sharing this. :)
on 5. January 2024, 06:59 by lidawer
I'm very confused about the rules.
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Perhaps I can help.
This constraint type points at (indexes) cells in the grid. Each digit in the cage points to a cell.
Let's look at the example. Take the digit 1 in the cage. The digit number points to a box. So the digit 1 points to box 1.
Next, digit's position points to the same position in the box. So the digit 1 is in the blue position, and it points at the blue position in box 1.
The same thing applies for the digit 3. It points to box 3, and points to the same position, colored green.
Finally, the 28 cage clue should be read as "two eights", meaning there must be two 8s in cells pointed at by digits in the cage. Since there are only two such cells, both must contain an 8.
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So if the number in the corner is 16 but there are 2 cells in the cage, does that mean that only one of the cells in the cage indexes to a 6?
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Yes, exactly!
