Cách chơi Anti-Knight Sudoku

Anti-Knight Sudoku is a variant where no two cells that are a chess knight's move apart may contain the same digit. A knight moves in an L-shape: two cells in one direction and one cell perpendicular. This adds a non-adjacent constraint that reaches across boxes and rows in ways standard Sudoku cannot.

A knight's move covers up to eight possible cells: two squares in any cardinal direction plus one square perpendicular. These eight cells can span across different rows, columns, and boxes — so the anti-knight constraint connects parts of the grid that standard Sudoku treats as independent.

Yes. The knight-move relationships are less intuitive than row/column/box constraints and require deliberate mapping. Easy puzzles are accessible once you visualise the knight's reach. Hard and expert puzzles use the constraint to create deductions that would be impossible without it.

Remembering that the constraint spans across boxes. It is easy to forget that placing a 5 in the top-left corner eliminates 5 from cells that are in a completely different box. Systematically checking all eight knight-reach cells after every placement is essential.

Yes — all standard techniques apply, with the knight-move relationships treated as additional elimination links. Naked pairs and hidden singles can be found by treating any two knight-move-related cells as a pair subject to uniqueness.

Easy puzzles take 8–18 minutes. Medium puzzles run 18–35 minutes. Hard puzzles average 35–65 minutes and expert puzzles often exceed 90 minutes. The key to faster solving is visualising the full knight-reach pattern automatically after each placement.