Anti-Knight Sudoku
No two cells a knight's move apart may contain the same digit
Easy
Anti-Knight Sudoku Easy
Medium
Anti-Knight Sudoku Medium
Hard
Anti-Knight Sudoku Hard
Expert
Anti-Knight Sudoku Expert
What is Anti-Knight Sudoku?
Anti-Knight Sudoku extends Sudoku with a chess rule: any two cells reachable from each other by a chess knight's move (2+1 squares in an L-shape) cannot share the same digit. Each cell has up to 8 potential knight-move neighbours. This creates a rich constraint network that is separate from and extends beyond the standard row/column/box rules.
At a Glance
| Constraint type | Anti-Constraints |
| Typical givens | 20–26 |
| Difficulty rating | ★★★☆☆ 3/5 |
| Avg. solve time — Easy | 5 min |
| Avg. solve time — Medium | 12 min |
| Avg. solve time — Hard | 24 min |
| Avg. solve time — Expert | 45 min |
How to Solve Anti-Knight Sudoku
| Technique | What it does | Level |
|---|---|---|
| Knight-Zone Mapping | For each cell, mark all potential knight-move destinations (up to 8 cells). None may share the same digit as the source cell. | Beginner |
| Corner and Edge Advantage | Corner cells have only 2 knight-move neighbours; edge cells have at most 4. These restricted zones are easiest to resolve first. | Beginner |
| Knight Chains | Placing a digit can eliminate it from a chain of knight-move positions that span diagonally across the grid. | Intermediate |
| Graph Coloring | Model the knight-move network as a graph and two-color it to find cells that cannot share a digit. | Advanced |
Average Solve Times
Easy
5 min
Medium
12 min
Hard
24 min
Expert
45 min
Frequently Asked Questions
What is a knight's move?
A chess knight moves in an L-shape: two squares in one direction, one square perpendicular (or vice versa).
How many knight-move neighbours does a centre cell have?
Up to 8 — the full L-shape set in all four diagonal orientations.