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Arctic Sudoku
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ExpertKiller

Minimum and maximum sums

What it is

The other cells of a cage can only be so large or small, which limits each cell.

How to spot it

For a cage, ask: what are the largest (or smallest) digits the other cells could hold? The difference to the sum is the least (or most) this cell can be.

Example

12123422123456789123456789123456789
  • Removed / placed
A cage of 22 in three cells: the other two cells are at most 9 + 8 = 17, so each cell is at least 22 − 17 = 5. 1–4 are removed from all three cells.

Used from level: Expert (Killer Sudoku)