Sudoku solver

[Dave Angel]

On 03/27/2015 09:25 AM, Chris Angelico wrote:
> On Sat, Mar 28, 2015 at 12:14 AM, Dave Angel <davea at davea.name> wrote:
>> But now I have to disagree about "true Sudoku puzzle."  As we said earlier,
>> it might make sense to say that puzzles that cannot be solved that way are
>> not reasonable ones to put in a human Sudoku book.  But why isn't it a "true
>> Sudoku puzzle"?
>>
>> Isn't the fact that one resorts to trial and error simply a consequence of
>> the fact that he/she has run out of ideas for more direct rules and the data
>> structures to support them?
>>
>> The simpler rules can be built around a list of possible values for each
>> cell.  More complex rules can have a more complex data structure for each
>> cell/row/column/box.  And when you run out of ideas for all those, you use
>> guess and backtrack, where the entire board's state is your data structure.
>
> At that point, it may make a fine mathematical curiosity, but it's not
> really a fun puzzle any more.

That's why I addressed my comments at Frank.  You and I are already in 
rough agreement about what makes a human game worthwhile: it has to be 
easy enough to be solvable, and hard enough to be challenging.  Those 
cutoffs differ from one person to another, and from one age group to 
another.  At one time (50+ years ago) I though Tic-Tac-Toe was tricky 
enough to be fun, but now it's always a draw, and only playable against 
a kid.  On the other hand, I play some "games" which I can only solve 
with the aid of a computer.  Is that "cheating"?  Not for some games.  I 
have some challenges for which I need/prefer to use a wrench, or a 
screwdriver, or a lawnmower.  That doesn't make them less fun, just 
different fun.

But I took Frank's comments as defining the "fine mathematical 
curiosity," and I have more interest in those than I generally do in 
"games".

Many games that I hear people talking about, I've never even tried.
I have a "TV set" which has never been hooked up to an antenna or cable. 
  Only to CD/DVD/BluRay/computer/tablet/cellphone.  So I'm a bit 
strange.  I still enjoy riding a motorcycle,  walking on the beach, or 
seeing a sunset from the backyard.



-- 
DaveA