Sudoku solver

[Chris Angelico]

On Sat, Mar 28, 2015 at 12:56 AM, Marko Rauhamaa <marko at pacujo.net> wrote:
> "Frank Millman" <frank at 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.

Not really. I already gave a broad generation algorithm, capable of
generating puzzles at any difficulty you choose. (Well, maximum
difficulty. If you tell it "generate HARD puzzles", it might still
generate a MEDIUM or EASY one. But you could post-filter for that.)
The only back-tracking required is at the last step, where it seeks to
minimize the number of clue digits - an optional step, and one that
involves very little backtracking. I think you subsequently posted
code which does broadly the same thing, but without the
difficulty-class checks.

ChrisA