About Bob Hanson's Su-Doku solver

Programs which generate, solve, and analyze Sudoku puzzles

Postby Bob Hanson » Fri Jan 02, 2009 3:00 am

A follow-up on this -- Sudoku Assistant now identifies Sashimi. There were a couple of bugs in the program yesterday, but these have been fixed.

You can check it out at

http://www.stolaf.edu/people/hansonr/sudoku/ex_A1s.htm

and

http://www.stolaf.edu/people/hansonr/sudoku/explain.htm#sashimi
Bob Hanson
 
Posts: 75
Joined: 04 December 2005

Postby 999_Springs » Fri Jan 02, 2009 4:30 am

Bob Hanson wrote:For example:

this one

So I think there may be some that are not reducible -- unless you see a smaller set here as well.

{r5c24 r7c1234}

Took me 2 seconds to spot it...
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Once upon a time I was a teenager who was active on here 2007-2011
999_Springs
 
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Postby Bob Hanson » Fri Jan 02, 2009 6:39 am

Superb work! Thanks very much for that -- there was a bug -- Sudoku Assistant was not looking for X-Wing-Sashimi. Now that that's fixed, I'm certain that the

n x n Rows == m x m Columns

grid equivalence carries over to a

n x n sashimi Rows == m x m sashimi Columns

equivalence.

I guess that is what you were trying to tell me in the first place.... that there's always a simpler alternative.

Probably a very simple proof of that.

In any case, thanks for the help -- Sudoku Assistant should be finding all Sashimi now, and finding always the smaller alternative.

When I'm done running the test examples, the "A1g" class will be gone -- all those are Sashimi.
Bob Hanson
 
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Joined: 04 December 2005

Postby 999_Springs » Tue Jan 06, 2009 3:52 am

You might consider combining almost-locked grids with your newly-discovered "almost-locked ranges":
Code: Select all
. . .|. . .|/ / 5
. 5 .|5 . .|5 5 5
. | .|| . .|/ / 5
--|--+|----+-----
. 5 .|5 . .|. . *
. | .|| . .|. . .
. | .|| . .|. . .
--|--+|----+-----
. 5 .|5 . .|. . *
. . .|. . .|. . .
. . .|. . .|. . .

*<>5

I don't know how useful they might be...

One thing I have noticed in your solver that seems not to have occurred before is the strange choice of subsets. Of course, for every naked subset there is a corresponding hidden one and vice versa, but your solver sometimes finds the larger subset.

Here you can use a naked pair instead of the hidden triple.

And your only example of a hidden quad can be replaced by a naked triple.
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Once upon a time I was a teenager who was active on here 2007-2011
999_Springs
 
Posts: 367
Joined: 27 January 2007
Location: In the toilet, flushing down springs, one by one.

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