GridWits
Extreme tier Technique 18 of 46 Used by Smart Hint

Remote Pairs

A connected chain of cells holding the same bivalue pair alternates between its two digits; a target that sees both chain colors can contain neither digit.

How it works

  1. 1A1, C2, C5 and F5 all hold exactly the same pair, {4, 6}, and each is a peer of the next — A1 and C2 through the top-left box, C2 and C5 down column C, C5 and F5 along row 5.
  2. 2Peers can't repeat a digit, so the chain alternates strictly: whichever of 4 and 6 A1 takes, C2 takes the other, C5 matches A1 again and F5 matches C2. Two colours, and one of them is right.
  3. 3F1 sees A1 across row 1 and F5 down column F — one cell of each colour. Between them those two hold both 4 and 6, so F1 can keep neither.
  4. 4Each neighbouring pair on its own is only a Naked Pair; the new eliminations appear once the chain reaches a cell that shares no unit with any single pair.

Play a Sudoku that needs this technique →

A 1 B 2 C 3 D 4 E 5 F 6 G 7 H 8 I 9 4 6 4 6 7 4 6 4 6 4 6 4 4 4 4 4 6
  • First colour in the chain
  • Second colour in the chain
  • Where the conclusion lands
  • Candidate ruled out
  • Strong link — At least one endpoint must be true.
Next in the ladder Jellyfish →

The four-line version of X-Wing and Swordfish — a digit's candidates across four rows fit inside the same four columns.