Anti-Knight Sudoku
3
1
7
2
8
9
9
1
8
2
4
9
1
3
5
1
9
7
5
8
1
7
4
7
5
5
9
1
2
8
4
3
7
4
1
6
8
2
Mistakes
0/3
Score
-
Time
00:00
Progress0%
Easy · Anti-Knight Sudoku
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How to play Anti-Knight Sudoku
Standard Sudoku rules apply. Additional rule: no two cells reachable by a chess knight's move (2+1 squares in an L-shape) may contain the same digit. The constraint is invisible — no markers on the board — so keep it in mind as you solve.
Full guide →
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 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.
How far does the anti-knight constraint reach?
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.
Is Anti-Knight Sudoku harder than regular Sudoku?
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.
What is the hardest part of Anti-Knight Sudoku?
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.
Can standard Sudoku techniques still be used?
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.
How long does Anti-Knight Sudoku take to solve?
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.