Sudoku technique guide

Grouped X-Chain Sudoku Technique

A Grouped X-Chain follows strong and weak links for one candidate, including grouped candidate positions. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.

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At a glance

Difficulty

Advanced

This is where Grouped X-Chain normally sits in a human solving path.

Family

Visual chain techniques

It belongs to the visual chain techniques group of Sudoku logic.

Main action

Usually remove candidates

Most technique moves reduce notes first. That often reveals a simpler placement afterwards.

What is Grouped X-Chain?

A Grouped X-Chain follows strong and weak links for one candidate, including grouped candidate positions.

The important thing is that this is logic, not guessing. You are using the current candidates to prove that a number must either go in one place, or cannot stay in another place.

In SudoSketch, this technique is designed to work with notes and Coach highlighting, so the key cells and removal cells can be shown clearly.

How Grouped X-Chain works

Focus on one candidate.
Follow alternating strong and weak links, allowing grouped positions when needed.
Use the chain endpoints to remove candidates that can see both ends.

When to look for it

Look for Grouped X-Chain after easier moves have stopped working. First check for naked singles, hidden singles, locked candidates and simple pairs. If those do not move the puzzle forward, this technique may be worth checking.

For learning, do not try to scan for every advanced technique at once. Pick one method, understand the shape, and practise spotting that one pattern.

Common mistake

Keep the chain alternating properly. Broken alternation means the conclusion is unsafe.

If you are unsure, rebuild the candidates first. Bad notes create bad logic, and Sudoku will absolutely punish you for it like a tiny spreadsheet goblin.

Grouped X-Chain FAQ

What is Grouped X-Chain in Sudoku?