Almost Locked Sets (ALS)
Extreme
Used by Smart Hint
Groups of cells just one candidate away from being "locked" are paired up to find eliminations that simpler subset techniques miss.
- First colour in the chain
- Cells that establish the pattern
- Where the conclusion lands
- Candidate ruled out
How it works
- A1 + B1 form an Almost Locked Set: two cells sharing three candidates {1, 2, 3} between them — one candidate away from being a locked pair.
- E1 + E2 form a second Almost Locked Set with {3, 4, 5}. Both sets share digit 3 as their only common candidate — the "restricted common candidate" linking them.
- Since 3 must resolve inside one set or the other, any cell that sees every 3 in both sets — like G1 — can have 3 eliminated.