[LRUG] Continuations

[Piers Cawley]

Andrew Stewart <boss at airbladesoftware.com> writes:

> On 15 Mar 2007, at 14:54, Daniel Lucraft wrote:
>> The point is that backtracking is OK for *solving* sudoku, but what
>> about generating them? In order for them to be 'human friendly', they
>> have to be solvable through logic, or at least only minimal search.  
>> And
>> then you have to order the constraints by how hard they are to  
>> apply by
>> people, and then you can create a difficulty rating by examining which
>> constraints get activated during propagation.
>
> Yes, that is a good challenge :)

Oh yes. I punted on that one. There's at least one generator written
in Perl that guarantees uniqueness, but the generated grids have no
symmetry, and there's no way of knowing how hard they are. There's a
sudoku game for Palms that, judging by its interface, seems to
generate grids at random and then runs its internal solver (which is a
'non-guessing' solver) against them and categorizes them based on the
level of inferences needed to find the solution. ISTR that it doesn't
generate symmetrical grids either.

-- 
Piers Cawley <pdcawley at bofh.org.uk>
http://www.bofh.org.uk/