Re: [SPOILER] Perl 'Easy' Quiz of the Week #2005-03-04 - attempt 2 w/ o attachments

On Mon, Mar 14, 2005 at 03:38:23PM -0000, Gillman John (Mr JG) wrote:

>Once read in, the grid is checked for validity, i.e. no duplicate numbers in
>a row, column or 3x3 block. Then before we actually start looking for a
>solution we do a bit of pre-processing to fill out the empty cells HoL above
>and to also construct a new one. First the new one; this is a HoL keyed by
>row, column or block identifier (group of nine) with the value being a list
>of possible digits that could be assigned to any empty cell in that group of
>nine. Once we have that information we can construct the list of possible
>digits for each empty cell by finding the intersection of the lists for the
>row, column and 3x3 block for this cell.

Interesting - it looks as though you're using my logical move 1 plus
guesswork. I am told that the "proper" sudoku puzzle does not require
guesswork at all, but I don't have a sufficient set of logical moves to
solve every case...

On the other hand your system seems to work faster than mine.

>The script was actually developed on a
>150MHz SPARC 10 which ain't so quick. I wasn't very good a permutations and
>combinations at school but are there any mathematicians out there who can
>come up with the number of possible Sudoku grids?

It's certainly less than 5e70 (which I believe to be the number of ways
of arranging the numbers, ignoring the other constraints: 81!/(9!)^9)

Roger