Sudoku solver

[Frank Millman]

"Marko Rauhamaa" <marko at pacujo.net> wrote in message 
news:87r3sdnw5t.fsf at elektro.pacujo.net...
>
>
> I post below a sudoku solver. I eagerly await neater implementations (as
> well as bug reports).
>

Here is another python-based sudoku solver -

http://www.ics.uci.edu/~eppstein/PADS/Sudoku.py

>From its docstring -

"A proper Sudoku puzzle must have a unique solution, and it should be 
possible to reach that solution by a sequence of logical deductions without 
trial and error.  To the extent possible, we strive to keep the same ethic 
in our automated solver, by mimicking human rule-based reasoning, rather 
than resorting to brute force backtracking search."

A neat feature is that, having printed the solution, it then lists every 
step it took in its reasoning process to arrive at the solution.

It solved Marko's original puzzle and Ian's puzzle in less than a second. It 
could not solve Marko's second one, returning "impossible" immediately.

Here is another one that does not use python, but uses SQL -

https://www.sqlite.org/lang_with.html

You will find it at the bottom of the page, under the heading "Outlandish 
Recursive Query Examples".

Frank Millman