Jigsaw · Hard

Naked Pair in Jigsaw Sudoku

Two cells in a house that hold the same two candidates. Those two digits are theirs.

The idea

When two cells in a house hold only the same two candidates, those two digits must go in those two cells, and no other cell in the house can use them.

In Jigsaw the pair can sit in a region, and then those digits are eliminated from the whole region.

Worked examples

2 positions from real Jigsaw puzzles on this site, the familiar case first. Step through each one: the board lights what each step talks about, and the arrows show what rules what out.

A pair in a row

Hard puzzle · Naked Pair

In row 4, look for two cells that hold the same two candidates between them.

Step 1 of 4Step 2 of 4Step 3 of 4Step 4 of 4

A pair in a region

Hard puzzle · Naked Pair

Both cells of the pair are in the lit region, so the region is cleared too.

Step 1 of 5Step 2 of 5Step 3 of 5Step 4 of 5Step 5 of 5

Where it fits

HardNaked Pair is a Hard technique: Hard Jigsaw puzzles are the first to need it.

The Classic Naked Pair lesson teaches it on a plain 9×9 board. The Jigsaw overview explains the rule and the levels.

Naked Pair in the other styles: Sudoku X, Thermo, Windoku, Arrow, Kropki.

Try it on a Hard Jigsaw puzzle. Next Step points it out when it is the move.

The worked examples, every step

A pair in a row

Hard Jigsaw puzzle · Naked Pair

  1. In row 4, look for two cells that hold the same two candidates between them.
  2. R4C2, R4C3 hold only {1, 5}. Those two digits must fill those two cells, so no other cell in row 4 can use them. Nor can a cell that sees both of them: R3C2 sees R4C2 in column 2 and R4C3 in region 1; R7C3 sees R4C2 in region 4 and R4C3 in column 3. The arrows point to the cells that lose them.
  3. Eliminate {1, 5} from R3C2, R7C3.
  4. Done: 1 is eliminated from R3C2, R7C3.

A pair in a region

Hard Jigsaw puzzle · Naked Pair

  1. Both cells of the pair are in the lit region, so the region is cleared too.
  2. In region 6, look for two cells that hold the same two candidates between them.
  3. R7C9, R8C9 hold only {1, 2}. Those two digits must fill those two cells, so no other cell in column 9 and region 6 can use them. The arrows point to the cells that lose them.
  4. Eliminate {1, 2} from R4C9, R5C9, R6C9.
  5. Done: 2 is eliminated from R4C9; 2 is eliminated from R5C9; 1 and 2 are eliminated from R6C9.

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