Re: /$sudoku/

On Apr 21, 2006, at 9:51 AM, Steven W. Orr wrote:

> Interesting. I would expect that rotating a sudoku matrix would not  
> have
> any impact in the difficulty of the problem. I remember from my old
> numerical analysis course (back before you young whippersnappers were
> born) we looked at something called the Hubbard or Hibbard constant  
> for a
> matrix. The deal was that if you multiplied a matrix by its  
> inverse, then
> there was something you would come up with that would tell you how  
> hard it
> was to invert the matrix. Of course you needed the inverse to  
> calculate it
> in the first place...

It's not the asymmetry of the problem that is at fault, but the  
asymmetry of the solution.  The regexp is a brute force, short- 
cutting solver that works from L->R and T->B.  That particular  
problem simply tickles the worst-case of the regexp, so it's brute  
forcing its way through a LOT of wrong solutions before hitting on  
the right one.

Chris
-- 
Chris Dolan, Software Developer, Clotho Advanced Media Inc.
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