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Subject: Re: Sudoku solver
references: <87r3sdnw5t.fsf@elektro.pacujo.net> <mailman.188.1427358005.10327.python-list@python.org> <87fv8sndw1.fsf@elektro.pacujo.net> <mf36kv$ko6$1@ger.gmane.org> <CAPTjJmpUxitmFq7tW-LT4JtwPU4cvzgLfDMj1XD_25piJuTmtA@mail.gmail.com> <551557B3.5090102@davea.name> <mailman.252.1427463342.10327.python-list@python.org> <87twx6lf15.fsf@elektro.pacujo.net> <55156489.9050200@davea.name>
From: Virgil Stokes <vs@it.uu.se>
To: "python-list@python.org" <python-list@python.org>
Date: Sat, 28 Mar 2015 19:36:44 +0100
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Xref: csiph.com comp.lang.python:88235

On 27-Mar-2015 15:09, Dave Angel wrote:
> On 03/27/2015 09:56 AM, Marko Rauhamaa wrote:
>> "Frank Millman" <frank@chagford.com>:
>>
>>> So what I am talking about is called a "satisfactory" puzzle, which is
>>> a subset of a "proper" puzzle.
>>
>> That is impossible to define, though, because some people are mental
>> acrobats and can do a lot of deep analysis in their heads. What's
>> satisfactory to you may not be satisfactory to me.
>>
>> Besides, looking for "satisfactory" patterns can involve a truckload of
>> trial and error.
>>
>
> I know, let's use "regular expressions"  <g>
>
>
If you are interested, I have written a python (wxPython GUI) for solving Sudoku 
problems. It even has a "hint" mode that can be used to lead you to a solution. 
I have tested it on the world's hardest Sudoku (published by a Finish 
mathematician)  and it solves it very fast. I have also written another version 
that finds ALL the solutions to any Sudoku problem (that has a solution) using 
an LP approach --- this is non-trivial. However, I have not been able to give a 
strict mathematical proof that it does indeed find all solutions.

If you wish to really understand the mathematics behind Sudoku then I suggest 
the book "Taking Sudoku Seriously" by Jason Rosenhouse and Laura Taalman (Oxford 
University Press, 2011). Unfortunately, they do not consider the LP approach in 
this book (an oversight IMHO).

--V. Stokes