Less-than indexes
(Published on 22. July 2026, 03:07 by Renbanter)
Click here to play on SudokuPad.
Classic: Standard 4×4 Sudoku rules apply (fill every row, column, and 2×2 box with the digits 1–4 exactly once).
"Less-than index" region: Divide the grid into two orthogonally connected regions, a small yellow region containing 3 cells and a large blue region containing 13 cells. r2c2 should belong to the yellow region and r3c1 to the blue region.
There is nothing special about the blue region, but every cell in the yellow region has the following "less-than index" property. A digit n placed in a yellow cell indicates that cell has exactly n neighbors (orthogonally or diagonally, a.k.a. a king's move apart) which are strictly less than n.
Kropke: The two digits joined by a white dot are consecutive.
This is only my second attempt at constructing a Sudoku puzzle, so I'm sure there will be kinks to work out; sorry in advance for any mistakes!
Solution code: Rows 3 and 4 in reading order
