Warp <war### [at] tagpovrayorg> wrote:
> scott <sco### [at] scottcom> wrote:
> > >  (A sudoku problem only makes sense if it's unambiguous, iow. it can be
> > > solved unambiguously without trial-and-error, only by pure deduction.)

> > Isn't trial-and-error a form of deduction?  ie "If I put a 4 in here, that 
> > square will need to be 3, and then that doesn't work so it must be a 6 in 
> > the original square".  Of course there are more complicated chains of logic, 
> > but essentially you try one number and see if it gives a valid result.

>   If trial-and-error was acceptable in a sudoku, then you could just as
> well give an empty sudoku grid for someone to solve.

>   The principle in sudoku puzzles is that they can be solved without having
> to guess anything. The chain of required deductions may go very deep in
> the hardest sudokus, but it's always possible to solve it without having
> to guess.

  By the way, another requirement for the sudoku to be unambiguous is that
only one solution must exist.

-- 
                                                          - Warp

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