Redundant Sudoku Rules

07/25/2012

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by   Bart Demoen, et al.

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The rules of Sudoku are often specified using twenty seven all_different constraints, referred to as the big. Using graphical proofs and exploratory logic programming, the following main and new result is obtained: many subsets of six of these big are redundant (i.e., they are entailed by the remaining twenty one ), and six is maximal (i.e., removing more than six is not possible while maintaining equivalence). The corresponding result for binary inequality constraints, referred to as the small, is stated as a conjecture.