Medium 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

Anti-King Sudoku at medium difficulty. Apply the king's constraint consistently after every placement — missed diagonal eliminations are the most common source of errors.

[
[
7
,
0
,
0
Mistakes
0/3
Score
-
Time
00:00
Try Hard 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 (Medium)
13 min

Solving Techniques for Medium 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
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

Master these, then take on Hard Anti-King Sudoku to learn Advanced techniques.

Techniques to Master at Medium

  • Hidden Singles technique — When counting where a digit can live in a box, discard every cell diagonally adjacent to that digit elsewhere — the king rule turns near-misses into hidden singles.
  • Obvious Pairs technique — Pairs are extra valuable here: both pair digits get banned from the eight cells around each pair cell, an elimination footprint no classic pair can match.

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 — Medium Anti-King Sudoku

What techniques help with medium Anti-King Sudoku?
At medium difficulty, combine standard techniques (naked pairs, hidden singles) with king's-move chain reasoning. Placing one digit creates a ripple of diagonal eliminations that can unlock cells several squares away. Track these chains carefully.
How does the king's constraint affect naked pairs in Anti-King Sudoku?
Naked pairs in Anti-King Sudoku are more powerful than in regular Sudoku. If two diagonally adjacent cells form a naked pair, neither digit can appear in any of the eight cells surrounding either cell of the pair — this generates far more eliminations than a standard naked pair.
What is a diagonal elimination chain in Anti-King Sudoku?
A diagonal elimination chain occurs when placing a digit in cell A eliminates it diagonally from cell B, which then forces a different digit into B, which eliminates yet another digit diagonally from cell C, and so on. Medium puzzles often require following chains of 3–4 steps.
How long does a medium Anti-King Sudoku take?
Most players complete a medium Anti-King Sudoku in 12–25 minutes. If you're stuck, systematically apply the king's constraint everywhere — it's easy to forget the diagonal restriction when focused on rows and columns.
Should I use pencil marks for medium Anti-King Sudoku?
Yes. At medium difficulty, pencil marks become important. Initialize your candidate list for each cell using row, column, and box constraints, then also eliminate candidates that appear in any of the eight surrounding cells. This extended initialization will immediately reveal more singles.

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