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HardChains and uniqueness

Remote Pair

A chain of cells all holding the same two candidates. The ends behave like a pair even when far apart.

What it is

A remote pair is a chain of bi-value cells that all show the same two candidates, each linked to the next by a shared unit. The digits alternate along the chain, so cells an even number of steps apart hold opposite values. If the chain has an even length, its two ends are opposites — meaning any cell seeing both ends cannot hold either digit.

How to spot it

Find several cells with identical candidate pairs and connect those that share a unit. Count the links: with an odd number of links the ends are opposite, and cells seeing both ends can drop both digits.

Worked example

Step through the reasoning below. Each step adds one layer: first the position, then the pattern, then the candidates involved, and finally what can be eliminated.

Step 1 of 4: The starting position

Pattern cells
1/7, 1/8, 5/8, 5/5
Digits
4, 9
Eliminations
1/5, 5/7

Press a marked square to point it out on the board above.

Why it matters

The remote pair is the easiest chain to follow because every cell in it looks the same. It is a natural first step into chaining, and it demonstrates the alternating logic that longer chains rely on.

Frequently asked questions

How long does the chain need to be?

At least four cells. With four the two ends are guaranteed opposite, which is what enables the elimination.

How is this different from a naked pair?

A naked pair needs both cells in the same unit. A remote pair connects cells across the whole board through a chain, so the two ends can be nowhere near each other.

Put it to use

Where you will meet it

Expert grids are the only place this pattern regularly decides the solve. Bring your notes.

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