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Arctic Sudoku
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MediumKiller

Locked candidates in cages

What it is

If a cage must contain a digit and lies within one row, column or box, that digit can be removed from the rest of that unit.

How to spot it

Find a cage whose combinations all use the same digit – for example a cage of 3 in two cells (1+2). If the cage lies in one row, column or box, the digit can't be anywhere else there.

Example

12312345631212125126
  • Basis
  • Removed / placed
The cage of 3 in r1c1–r1c2 must be 1+2, and it lies in both row 1 and box 1. So 1 and 2 are removed from r1c5 (row 1) and r2c3 (box 1).

Used from level: Hard (Killer Sudoku)