Expert Anti-King Sudoku
4
9
1
6
3
8
1
3
5
4
8
7
8
6
3
5
2
7
9
7
5
8
4
6
Mistakes
0/3
Score
-
Time
00:00
Progress0%
♚ King's move constraint active
Expert · Anti-King
All Anti-King →
How to play Anti-King Sudoku
Standard Sudoku rules apply. Additional rule: no two diagonally adjacent cells (or orthogonally adjacent) may share the same digit. A king on a chess board can reach all 8 surrounding cells - None of those cells can share a digit.
About Anti-King Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Anti-Constraints
Typical Givens
22–28
Avg. Solve (Medium)
13 min
Anti-King Sudoku adds a chess-inspired constraint: cells that would be reachable in a single king move (orthogonally or diagonally adjacent) cannot share the same digit. This extends the non-repeat rule beyond rows, columns, and boxes to include diagonal neighbours, significantly tightening the constraint space throughout the grid.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Diagonal Exclusion | The king constraint extends the exclusion zone to all 8 neighbours including diagonals. Apply diagonal exclusions before standard row/col/box logic. | Beginner |
| Corner Restriction | Corner cells (e.g., r1c1) only have 3 king-move neighbours. Start with corners and edges to build initial placements. | Intermediate |
| King-Chain Elimination | When a digit is placed, eliminate it simultaneously from all 8 surrounding cells. | Intermediate |
| Parity via King's Move | In Anti-King, consecutive digits often become mutually king-move incompatible — trace valid placement paths using this property. | Advanced |
Average Solve Time by Difficulty
Easy
5 min
Medium
13 min
Hard
26 min
Expert
48 min