Sudoku as a Constraint Problem Helmut Simonis
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@MISC{_sudokuas,
author = {},
title = {Sudoku as a Constraint Problem Helmut Simonis},
year = {}
}
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Abstract
Abstract. Constraint programming has finally reached the masses, thousands of newspaper readers (especially in the UK) are solving their daily constraint problem. They apply complex propagation schemes with names like “X-Wing ” and “Swordfish ” to find solutions of a rather simple looking puzzle called Sudoku. Unfortunately, they are not aware that this is constraint programming. In this paper we try to understand the puzzle from a constraint point of view, show models to solve and generate puzzles and give an objective measure of the difficulty of a puzzle instance. This measure seems to correlate well with grades (e.g. easy to hard) that are assigned to problem instances for the general public. We also show how the model can be strengthened with redundant constraints and how these can be implemented using bipartite matching and flow algorithms. 1
