Anti-King Sudoku

How to play anti-king sudoku

In anti-king sudoku, cells a chess king's move apart, including diagonal neighbors, can't hold the same digit. Within a box that changes nothing, but across a box border it rules out the corner touches.

The rule shapes how each digit can snake through a band of three boxes, which is where most anti-king logic happens.

Anti-king sudoku: full lesson

See the rule in 15 seconds

At a glance

• Cells that touch, even at a corner, can't repeat a digit.
• Only diagonal touches across box borders are new.
• Each 2x2 block of cells holds four different digits.
• Also called no-touch sudoku.

The king's move

The marked cells are a king's move from the 5. Inside its own box they were already ruled out, and side neighbors share a row or column, so the new eliminations are the corner touches across box borders.

How to start an anti-king sudoku

1. Check corner touches

   When a digit sits on the edge of a box, the cells diagonally across the border can't repeat it.

2. Think in bands

   A digit runs through three boxes in a row in three different rows. With anti-king, it can't step to a diagonal neighbor as it crosses a box border.

3. Use the 2x2 rule

   Any 2x2 block of cells holds four different digits. That makes pairs across box borders more powerful than usual.

4. Combine with pointing

   If a digit in one box can only be in two cells at the box's edge, a cell diagonally touching both can't be that digit.

5. Fall back on classic technique

   Anti-king adds eliminations, not new kinds of logic. Singles and pairs do most of the work.

Common mistakes

Five levels, no guessing

Every puzzle has one solution, proved when it is set, and our solver finishes it by logic alone. The level is the hardest step the solve needs. Here is what each level asks of a anti-king puzzle:

1. EasySingles, counting corner touches as extra eliminations.Play Easy
2. MediumPointing pairs and box/line reductions.Play Medium
3. HardNaked and hidden pairs and triples.Play Hard
4. ExpertX-Wings, Skyscrapers and wings.Play Expert
5. FiendishColoring and chains. Never a guess.Play Fiendish

The daily variant rotates through 11 kinds, so a anti-king daily comes round about every 11 days. Past dailies

Hand-set anti-king puzzles

Our levels are a good start. For more, Explore has 62 anti-king puzzles made by people, from Logic Masters and Cracking the Cryptic. A few of the most popular:

Circular Reasoningby vitrayCapsulesby ul-RhymmParity Poopersby aleph-0Sorry, Wrong Numberby billybethArrow Regionsby QmazingBorder Arrowsby Aad van de WeteringBroken 358 Tearsby Bha-GuCaterpillar Thermometerby Md88keys

Setters with the most anti-king puzzles:

• olima 5
• billybeth 4
• Vitray 3
• addie 3
• Aad van de Wetering 3
• Eric Rathbun 2
• Md88keys 1
• The Bard 1
• NateagXXVII 1
• kierownik 1

Often combined with:

• Anti-King + Killer 20
• Anti-King + Anti-Knight 19
• Anti-King + Kropki 16
• Anti-King + Arrow 14
• Anti-King + German Whispers 10
• Anti-King + Thermo 8
• Anti-King + Ratio 8
• Anti-King + Non-Consecutive 6
• Anti-King + Non-Touching 6
• Anti-King + Consecutive 6

All 62 anti-king puzzles in Explore · Make your own anti-king sudoku

Questions

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