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The Killer Cage Convention

Killer Sudoku 'dog legs'
Killer Sudoku 'dog legs'

In Killer Sudoku clues are placed inside 'cages' - which ring a certain number of cells. The clue number is the sum of the solutions to those cells. It is theoretically possible for a cage to contain two of the same numbers if the cage forms an 'L' shape or 'dog-leg' over two boxes. Examples are to the right in bold red and green.

From the earliest days of Killer Sudoku there has been a convention that no cage should contain duplicate numbers - which applies to these special types of cage. If a cage could contain duplicate numbers then it would greatly increase the number of combinations of solutions.

There are six 'dog-legs' in this example, some have A-A, B-B etc showing where possible duplicate numbers could go - but do not.

All the puzzles on this site and ones I publish conform to this convention, but you might find other publishers ignore this constraint. If you enter such a puzzle into the Killer Solver it will not work.

The convention does not apply to KenKen or Kendoku as designed by the people at


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Article created on 30-July-2011. Views: 28063
This page was last modified on 30-July-2011.
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Copyright Andrew Stuart @ Syndicated Puzzles Inc, 2011