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Sudoku technique · Specialty reference · reference
Longer ALS chains
Link several almost locked sets through restricted common candidates. Track which digit a missing endpoint forces into the next set.
How to spot it
Use ALS-XZ as the two-set starting case.
The common mistake
Overlaps, double links, and adjacent restricted digits require additional care. This app does not auto-detect them.
Learn this first
ALS-XZ.
Further reading: hodoku.sourceforge.net