Indexers Playground
(Published on 4. January 2026, 20:01 by Kutsumi Hane)
In a standard Sudoku grid, each cell can be identified in two different coordinate systems.
One way is by its row and column, e.g. the cell R5C7 lies in row 5 and column 7.
The other way is by its box and position index, e.g. the cell B6P4 lies in box 6 at position 4 within that box.
Actually, both notations refer to the very same cell in the 9×9 Sudoku — R5C7 is identical to B6P4.
Based on this dual coordinate system, we introduce two pairs of corresponding indexer constraints as follows:
One way is by its row and column, e.g. the cell R5C7 lies in row 5 and column 7.
The other way is by its box and position index, e.g. the cell B6P4 lies in box 6 at position 4 within that box.
Actually, both notations refer to the very same cell in the 9×9 Sudoku — R5C7 is identical to B6P4.
Based on this dual coordinate system, we introduce two pairs of corresponding indexer constraints as follows:
Rules:
Normal Sudoku rules apply, requiring that each row, column, and 3×3 box contains the digits 1-9 exactly once. Additionally:
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·Row indexer:
A marked cell in row X indicates the row in which the digit X appears in the same column. (Colored in blue)
·Column indexer:
A marked cell in column X indicates the column in which the digit X appears in the same row. (Colored in red)
·Box indexer:
A marked cell in box X indicates the box in which the digit X appears at the same position. (Colored in green)
·Position indexer:
A marked cell in position X indicates the position in which the digit X appears in the same box. (Colored in yellow)
Here is how the different indexers (row, column, box, position) work on a standard 4x4 Sudoku grid:
Here you can solve this puzzle online:
Solve on SudokuPad
The difficulty is probably 1-2 stars. I wish you joyful solving!
The difficulty is probably 1-2 stars. I wish you joyful solving!
Solution code: Digits in row 8.
Last changed on on 6. January 2026, 01:40
Solved by CaseyM, cryptique, gdc, milxqueen, SKORP17, Counterfeitly, Dermerlin, Fisherman, MaxSmartable, jalebc, ManniMensen, flaemmchen, HeyItsErin, prismoid, dzamie, supersim2000, walid_tun, sparkymanu, Nagesh, zrbakhtiar, drmegadude, TeddieMilo, Gizmo, drf93, CitrusGremlin, JVA, Qodec, abadx, 72kchunshuai, Aidan488, zhangjinyang
Comments
on 8. January 2026, 17:54 by Qodec
Perfect way to introduce this constraint, enjoyed that!
(Perhaps explicitly specify that disjoint constraint doesn't apply, because of what it does to box indexers.)
on 8. January 2026, 15:08 by JVA
Imma be honest, I used Excel formulas to figure out what goes where
on 6. January 2026, 22:15 by walid_tun
Very creative idea, I am looking forward for same kind puzzles
on 5. January 2026, 20:08 by prismoid
Neat ruleset, would like to see it applied to a more challenging puzzle
