Easy Anti-King Sudoku

No two identical digits may touch diagonally (like a chess king's move). Every cell has up to 8 restricted neighbours.

Easy Medium Hard Expert

New to Anti-King Sudoku? The king's-move constraint eliminates extra candidates — great for learning how diagonal restrictions change the puzzle.

[
[
1
,
0
,
9
Mistakes
0/3
Score
-
Time
00:00
Try Medium Anti-King Sudoku →
Progress0%
♚ King's move constraint active

What is Anti-King Sudoku?

Difficulty
★★★☆☆
3/5
Constraint Type
Anti-Constraints
Typical Givens
22–28
Avg. Solve (Easy)
5 min

Solving Techniques for Easy Level

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

Ready to go deeper? Try Medium Anti-King Sudoku to unlock Intermediate techniques.

Techniques to Master at Easy

  • Last Possible Number technique — Cross off candidates from all eight touching cells, not just row, column, and box — interior cells lose up to four extra candidates from their diagonal neighbours.
  • Last Remaining Cell technique — A placed digit forbids its four diagonal neighbours too, so "only one legal cell" situations appear early around any cluster of givens.

Average Solve Time by Difficulty

Easy
5 min
Medium
13 min
Hard
26 min
Expert
48 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Anti-King Sudoku →

Related Variants

Anti-Knight Sudoku

The companion chess constraint — the forbidden repeat jumps a knight's move instead of one diagonal step.

Anti-Consecutive Sudoku

Forbids a value relationship instead of a position: neighbours may touch, but their digits can't be consecutive.

Non-Consecutive Sudoku

Another global anti-rule solved with the same reflex — every placement immediately bans candidates around it.

Frequently Asked Questions — Easy Anti-King Sudoku

What is Anti-King Sudoku?
Anti-King Sudoku is a Sudoku variant with one extra rule: no two cells that are diagonally adjacent (touching at a corner) may contain the same digit. This mimics a chess king's move — a king can reach all eight surrounding squares, so none of those squares can share a digit with the king's cell.
How do I start solving easy Anti-King Sudoku?
Start with the standard Sudoku approach — find cells with only one candidate using row, column, and box elimination. Then apply the king's-move constraint: whenever you place a digit, also eliminate it from all eight surrounding cells, not just the orthogonal neighbors.
How is Anti-King Sudoku different from regular Sudoku?
Regular Sudoku only forbids repeats within rows, columns, and 3×3 boxes. Anti-King Sudoku adds a diagonal-adjacency restriction. Digits that sit diagonally touching each other must always be different. This extra constraint means many placements valid in regular Sudoku are illegal here.
Does the king's-move constraint make the puzzle easier or harder?
The extra constraint actually helps solve the puzzle by eliminating more candidates per placement. Each digit you place removes it from up to eight neighbors instead of just the row, column, and box. At easy difficulty this makes quick work of many cells.
Are there no visual markings showing the king's-move constraint?
Correct — the king's-move constraint is invisible on the board. There are no lines or shading to indicate it. You must remember to apply it yourself: after placing any digit, scan all eight surrounding cells and remove that digit from their candidate lists.

More questions? See the full Anti-King Sudoku guide.