Put in each row, in each column and in each 3x3 block the number from 1 to 9. In addition orthogonally next but one cells (rows/columns +- 2) must not contain next but one digits ( +- 2).
Digit 3 in r8c7 prevents digit 1 (and digit 5) in r8c5 and in r8c9, hence in row 8 there is only one cell left for digit 1: r8c4.
Solution code: The first and the ninth row
on 18. July 2023, 07:06 by uvo_mod
Added Sudoku tag.
on 27. May 2012, 20:57 by CHalb
Für mich überraschend im Lösungsweg und eine tolle Konstruktion.