♔ How to play Anti-King Sudoku

By Miguel Arechaga

Anti-King Sudoku is the sister variant of Anti-Knight. It borrows a rule from chess: two cells a king could touch (the adjacent ones, including diagonals) can't share a number. Since the orthogonal cells are already covered by the row and column rules, in practice the rule adds the four diagonals. Here's how to play.

What is Anti-King Sudoku?

It's a standard 9x9 sudoku with the chess king restriction added: two cells that touch diagonally can't contain the same number. All the other sudoku rules stay the same.

Rules and how to play step by step

1. The sudoku rules apply: 1 to 9 without repeats in each row, column and 3x3 box.
2. In addition, two cells that touch diagonally (a king's move) can't hold the same number.
3. You start with some clue cells and fill in the rest with logic. Every puzzle has a unique solution.

Tips to solve Anti-King Sudoku

• Watch the short diagonals: when you place a number, the (up to four) cells that touch it diagonally are blocked for that number.
• The corners between boxes: the rule is especially useful where four boxes meet, since it affects cells from different boxes.
• A given number can't form a continuous diagonal chain; that rules out many placements.
• Combine the king rule with the classic elimination techniques of sudoku.

How it differs from regular sudoku

Compared to classic sudoku, Anti-King adds diagonal relationships between neighboring cells that regular sudoku doesn't control. It's the perfect companion to Anti-Knight Sudoku. If you like variants with extra restrictions, you'll also enjoy other sudoku variants.