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Arctic Sudoku
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ExpertKiller

Combinations across cages

What it is

Cages in the same row, column or box can't use the same digits, which rules out combinations.

How to spot it

Compare the combinations of cages that share a unit. If one cage needs a digit, other cages in the unit can't use it.

Example

12123456371212123456123456
  • Basis
  • Removed / placed
The cage of 3 in row 1 is 1+2. The cage of 7 in the same row could be 1+6, 2+5 or 3+4, but 1 and 2 are taken – so it must be 3+4.

Used from level: Expert (Killer Sudoku)