Sudoku solver

[Ian Kelly]

On Wed, Mar 25, 2015 at 1:37 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> John Ladasky <john_ladasky at sbcglobal.net>:
>
>> On Wednesday, March 25, 2015 at 4:39:40 AM UTC-7, Marko Rauhamaa wrote:
>>
>>> I post below a sudoku solver. I eagerly await neater implementations (as
>>> well as bug reports).
>>
>> So, it's a brute-force, recursive solver? The code is nice and short.
>> But I bet it takes a long time to run.
>
> Try it.
>
> The C version takes milliseconds to complete (usually). The Python
> version can take the bigger part of a second.

The test puzzle that you posted has 23 values already filled in. How
does it perform on harder puzzles with only 17 clues (the proven
minimum)? One would expect it to be around a million times slower.