Remote Pairs

Remote Pairs is your gentle introduction to chain logic. It uses a run of cells that all share the same two candidates, linked so that their values alternate - and from that alternation you can make eliminations at the ends of the chain.

What is a Remote Pair chain?

Start with a naked pair - two cells with, say, {4, 9}. If another {4, 9} cell sees one of them, it's forced to the opposite value, and you can keep going: each new {4, 9} cell that sees the last one flips the value again. Follow such a chain and the cells alternate 4-9-4-9 along its length. Two cells an even number of steps apart hold opposite values - so any cell seeing both of them can hold neither 4 nor 9.

Three {4, 9} cells form a chain (indigo). The two ends hold opposite values, so a cell seeing both (red) can be neither 4 nor 9.

Step by step

Find a run of cells all holding the same two candidates, each seeing the next.
Trace the alternation. Values flip along the chain: 4, 9, 4, 9…
Look at cells an even number of links apart - they hold opposite values.
Eliminate both digits from any cell that sees both such ends.

Why it's a good first chain

Most chain techniques ask you to track several different digits as you hop from cell to cell, which takes practice. Remote pairs keep things simple: every link in the chain uses the same two candidates, so there's only one thing to follow. That makes it the ideal place to get comfortable with the idea that a run of linked cells forces a conclusion at its ends - the same idea that powers colouring and the longer chains beyond it.

Common mistakes

Different candidate pairs. Every cell in the chain must share the same two digits - the moment one differs, the chain breaks.
Odd separation. The elimination works between cells an even number of links apart; ends an odd distance apart hold the same value, which tells you nothing new.
Chaining cells that don't see each other. Each cell must genuinely see the next - share a row, column or box - or the alternation doesn't hold.

Which Sudoku types is this best for?

The same logic applies across variants, but it pays off more in some than others.

Works Classic Sudoku A gentle introduction to chain logic on harder grids. → Limited Killer Sudoku Uncommon in Killer. → Works Sudoku X Diagonals lengthen the chains available. → Limited Samurai Sudoku Rarely the fastest route. →

Where to practise this

This technique starts paying off at Expert, which is where puzzles first stop yielding to anything simpler. Reading about a pattern and spotting it on a live grid are different skills - the second one only comes from playing.

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Related techniques

Naked Pair - Sudoku Elimination Technique Two cells in a unit holding the same two candidates claim those digits, removing them elsewhere in the unit. X-Wing Sudoku Technique Explained One digit confined to the same two columns across two rows (or vice versa) - eliminate it from the rest of those lines. XY-Wing Sudoku Technique (Y-Wing) Explained A pivot cell with two candidates links two pincer cells; the digit they share is removed from any cell both pincers see. Swordfish Sudoku Technique Explained One digit confined to the same three columns across three rows (or vice versa) - eliminate it from the rest of those columns.