That doesn't make any sense: if you have a 15-clue puzzle with a unique solution, you can fill in any remaining square with its correct value to produce a 16-clue one. --Michael On Mon, Jan 9, 2012 at 10:39 AM, James Cloos <cloos@jhcloos.com> wrote:
The earlier report I read on this (possibly in arxivblog) said that they had only proven that there were no 16-clue puzzles with unique solutions, and that <13 clue puzzles had been ruled out by others.
Whether 13, 14, or 15 clue puzzles with unique solutions exist is still, according to that report, an open question.
The brute force search on 16 clue puzzles took a year; I believe it said 7 million core-hours.
-JimC -- James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6
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