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sudoku break

December 13, 2013

While in Warwick last week, one evening after having exhausted my laptop battery, I tried the following Sudoku (from Libération): and could not even start. As it happened, this was a setting with no deterministic move, i.e. all free/empty entries had multiple possible values. So after trying for a while and following trees to no […]

random sudokus

June 4, 2013

In a paper arXived on Friday, Roberto Fontana relates the generation of Sudoku grids to the one of Latin squares (which is unsurprising) and to maximum cliques of a graph (more surprising). The generation of a random Latin square proceeds in three steps: generate a random Latin square L with identity permutation matrix on symbol […]

tak1ng sudoku ser1ously

March 14, 2013

“There is something deeply satisfying in encountering opacity.” (p.9) I think it was last summer at the Australasian Statistics conference in Adelaide that I saw this book by Jason Rosenhouse and Laura Taalman, Taking Sudoku seriously: The math behind the World’s most popular pencil puzzle. (Or was it in Kyoto at the ISBA meeting?!) In […]

simulated annealing for Sudokus [2]

March 17, 2012

On Tuesday, Eric Chi and Kenneth Lange arXived a paper on a comparison of numerical techniques for solving sudokus. (The very Kenneth Lange who wrote this fantastic book on numerical analysis.) One of these techniques is the simulated annealing approach I had played with a long while ago.  They seem to use the same penalisation […]

Sudokus with minimum number of clues

January 9, 2012

Yesterday, I spotted on a Spanish post on the minimal number of clues to solve a Sudoku in a unique way. The original paper was posted on arXiv on January 1, in the Data structure and algorithms category. The authors, Gary McGuire, Bastian Tugemann, and Gilles Civario from University College Dublin, have shown by […]