The New Sudoku Players' Forum

[yj_hong]

Thousands of Sudoku sets with multiple difficulty levels
ready on WEB for your self-challenge. Go to URL:

http://www.mobileshortcut.com/GAMES/sudoku.htm

Have fun!

[evert]

This one came from the very hard:

Code: Select all

 ; ;9;3; ;2;7; ; ;
4; ; ; ; ; ;6; ; ;
 ; ; ; ; ; ; ; ; ;
 ; ; ; ; ; ; ; ; ;
2; ; ;1;7; ; ;8;3;
 ; ;6; ; ; ; ; ; ;
 ; ;8;2; ; ;3; ;4;
9; ; ; ; ; ; ; ; ;
 ; ; ; ; ;3; ; ; ;

I have the impression it has more solutions:

Code: Select all

8;6;9;3;4;2;7;1;5;
4;2;7;5;1;9;6;3;8;
5;1;3;8;6;7;2;4;9;
3;4;1;9;2;8;5;6;7;
2;9;5;1;7;6;4;8;3;
7;8;6;4;3;5;9;2;1;
6;7;8;2;5;1;3;9;4;
9;3;2;7;8;4;1;5;6;
1;5;4;6;9;3;8;7;2;

8;5;9;3;6;2;7;4;1;
4;7;2;8;1;9;6;3;5;
6;3;1;7;5;4;2;9;8;
5;1;7;9;3;8;4;2;6;
2;9;4;1;7;6;5;8;3;
3;8;6;4;2;5;1;7;9;
1;6;8;2;9;7;3;5;4;
9;2;3;5;4;1;8;6;7;
7;4;5;6;8;3;9;1;2;


[yj_hong]

Excellent work evert!

And you're correct, the Sudoku sets on M3S do not necessarily come with unique solution.

Unfortunately our generator is quite "single-minded" and knows of only
one solution. We may put in accompany solver later on, but in the mean
time, if you're right (solution), you're right

We apologize for the incapability of identifying multiple solutions, and the possibility of irritating you with the wrong check answer response.

Happy Sudoku!

(Curious, how did you get to more than one solution on the VERY HARD one?
Do you have any recommendation on approaches/tips?)

[tso]

You've jumped the gun by putting up a Sudoku site before you know how to create one -- or even know what one is. By *definition*:

1) A Sudoku has symmetry. Your puzzles do not.
2) A Sudoku has one and only one solution. Your puzzles do not. For example, I just got this one from your site:

Code: Select all

+---+---+---+
|.8.|.43|...|
|.5.|...|7.3|
|.3.|...|...|
+---+---+---+
|3..|1..|...|
|...|.3.|61.|
|1..|...|...|
+---+---+---+
|5..|3..|...|
|..3|9..|...|
|...|...|83.|
+---+---+---+

According to SadMan Sudoku, it has over 15,000 solutions! What's the point? Why not just publish a blank grid?

[dukuso]

You've jumped the gun by putting up a Sudoku site before you know how to create one -- or even know what one is. By *definition*:

1) A Sudoku has symmetry. Your puzzles do not.
2) A Sudoku has one and only one solution.

.., it has over 15,000 solutions! What's the point? Why not just publish a blank grid?

1) well, I think symmetry isn't required here in the board.
We've always used the name sudoku here for nonsymmetrical
ones too. But you're right, we should use another name.
Suggestions ? Can we aree on one ?
Maybe UQWHWBC for unique solution QWH with boxes constraint,
doesn't sound good.
NPP for number place puzzles looks good.
uNPP for unique solution NPP
suNPP for symmetric uNPP
+NPP NPP with >=1 solutions
-NPP NPP with 0 solutions

2) I could also ask:
What's the point for unique solution puzzles ?
Usually in real world you have a problem and you want to solve
it and you don't know whether there is a solution. No matter
how many solutions there are, one is sufficient.
Indeed, QWH instances can have any number of solutions.


Guenter.

[yj_hong]

All points well taken.

Let me say this then, M3S Sudoku is here as the poor man's time-killer, and casual players' easy starting point. It is not intended to pass all the "professional definitions", but it is hoped that its existence does bring fun to those who'd accept the M3S Sudoku as is.

I hope there's enough tolerance for such common sense Sudoku ?

[Moschopulus]

You've jumped the gun by putting up a Sudoku site before you know how to create one -- or even know what one is. By *definition*:

1) A Sudoku has symmetry. ...

Is symmetry part of the definition, or a convention that all newspapers seem to adopt? I don't see symmetry as part of the definition of sudoku on the wikipedia page.

[tso]

Let me say this then, M3S Sudoku is here as the poor man's time-killer, and casual players' easy starting point.

Again, your puzzles are not Sudoku -- barely even puzzles. It's a *terrible* place for the casualy player to start -- as they may very well decide that they do not like these types of puzzles and may not realize that it is your site, not Sudoku that are the issue.

You have opened a Sushi restaurant that doesn't serve Sushi, but instead serves only hamburgers, but you insist on calling them "sushi".

You've jumped the gun by putting up a Sudoku site before you know how to create one -- or even know what one is. By *definition*:

1) A Sudoku has symmetry. Your puzzles do not.
2) A Sudoku has one and only one solution.

.., it has over 15,000 solutions! What's the point? Why not just publish a blank grid?

1) well, I think symmetry isn't required here in the board.

Agreed -- but there's a vast -- subjective I know -- difference between puzzles here to study, to look for solving methods, unusual constructions, etc -- than a website that creates them for the public to solve. I wrote to one person who creates puzzles that are intentionally not symmetrical. He says that there are more possibilities for interesting solving situations if those constraints are lifted -- which I agree to in spirit -- but he actually makes no effort in that direction, just creating them at random, rating them by difficulty alone and publishing them. Unless there is a specific reason NOT to make the puzzle symmetrical, then it is my opinion that it is just sloppy.

We've always used the name sudoku here for nonsymmetrical
ones too. But you're right, we should use another name.

Number Place has been in use continuously since the middle 1970's.

2) I could also ask:
What's the point for unique solution puzzles ?
Usually in real world you have a problem and you want to solve
it and you don't know whether there is a solution. No matter
how many solutions there are, one is sufficient.
Indeed, QWH instances can have any number of solutions.

Oh, come on, you're just trying to be difficult. Tell me, have you *been* to this site? Are you going to waste 30 seconds of your life attempting to solve one of these monstrosities? 15000 solutions? Your questions are disingenuous. Tell me, will you direct others to this site? Do you think visiting this site will increase or decrease the chance that a novice will become a regular Sudoku solver? Do you think there are not enough Sudoku with one solution to fill up your time that we must resort these? If the programmer dosn't put any effort towards making a reasonable puzzle, will you waste your effort solving them? His site is not "the real world". These are not problems to overcome, but puzzles to solve. Not that a puzzle *must* have a unique solution to be correctly called a puzzle. There are plenty of good puzzles with the challenge to find the *shortest* solution or *quickest*, etc. But a Sudoku *does* have a unique solution by definition -- unless you stipulate otherwise. Here's one for you:

Code: Select all

........
........
........
........
...1....
........
........
........

Will you be spending your lunchtime solving my ingenious construction?

In your opinion, do you think the person who made this site wants his puzzles to have 1000's of solutions? Do you think he wants to be informed that his puzzles are malformed? Are you helping him by defending his site?

You've jumped the gun by putting up a Sudoku site before you know how to create one -- or even know what one is. By *definition*:

1) A Sudoku has symmetry. ...

Is symmetry part of the definition, or a convention that all newspapers seem to adopt? I don't see symmetry as part of the definition of sudoku on the wikipedia page.

Nikoli coined the word "Sudoku", defining it as a Number Place puzzle with 30 or less symmetrically placed. This hasn't changed in the 20+ years they've been publishing them. I would agree that a puzzle wth 36 randomly place clues is still a Sudoku. I would agree that a crossword would still be a crossword if it weren't symmetrical -- don't see too many of those outside of creations by school kids and cheesy company newsletters. Not all newspapers stick to the rule.

[dukuso]

no, I was not referring to that webpage. I don't know how
"good" the puzzles are.
There exist also good puzzles with multiple solutions,
e.g. the well known 12 pentominoes into 6*10 rectangle.

Having few solutions makes the puzzle harder.
The same can be achieved by increasing the grid-size

The latter is what is usually studied with QWH-problems.

Maybe just because they can be easier generated if multiple
solutions are allowed.

It's an interesting question whether unique solution NPPs or QWHs
can be faster generated or solved ? (for larger sizes, say
30*30)

[udosuk]

Don't understand about the fuss here. So this guy is putting up a site, which generate puzzles which look like sudokus but doesn't have unique solutions. And tso is so angry to the fact that the word sudoku appears in the site and fears that it will give a bad name to the puzzle and drive away future interested puzzlers...

Well as long as the site doesn't charge people for playing (that would be downright fraud) I don't see the big deal. If people played there and found the puzzles not funny to play at all (which they'll probably do) and they stop there and think that sudoku is just a crappy game and all those sudoku addicts over the world are just boring geeks who have nothing else better to do, then they must be very ignorant people and it's their own loss that they miss out on this great genre of puzzles. But don't underestimate the intelligence level of the average people surfing the net!

I suppose what tso wants is the site to put up a banner inside, saying "The puzzles provided here are just cheap ones that doesn't necessary have a unique solution, and shouldn't really be called sudokus. There are much better sites somewhere else that give valid sudoku puzzles and serious puzzlers should go and look for those sites instead of staying here and feeling disgusted about the quality of our puzzles..." I don't think your wish will be granted...

[dukuso]

"..There are much better sites somewhere else that give valid sudoku puzzles and serious puzzlers should go and look for those sites instead of staying here and feeling disgusted about the quality of our puzzles..." I don't think your wish will be granted...

yes and all the trash sudoku books should have a big red band around them with the words "this is trash" ;-)
(But copyright trash ;-).
Ahh, yes and Euler didn't invent them.

But seriously, I would appreciate, if Tso would make a webpage
where he reviews Sudoku-books.
He's certainly qualified.
Anyone wants to host it ? [Wayne ? ;-) ]

[Pappocom]

Yes, if you want me to host reviews of books, I will.

I am tolerant of criticism of myself, so that's not an issue. The reviews can say whatever they like.

I do moderate this site a little, but not for posts which criticise me. I am apt to clamp down on posts which infringe Intellectual Property rights (especially the IP rights of others), on posts which use questionable language, on posts which promote generator programs and on posts which get close to being inflammatory. But I don't censor posts which criticise me. I was a Judge for 15 years. You get used to being criticised.

- Wayne

[dukuso]

please specify, what you consider IP.
According to New-Sealand- laws ? Where can I look these up ?
Do you consider sudokus posted to the web
and then redistributed here as "Infringe of Intellectual Property rights" ?

[Pappocom]

Don't panic.

If anything has been posted here and remains here, it's OK. So just keep doing what you've been doing.

- Wayne

[evert]

Excellent work evert!

Thanks for your compliment - I'll accept it for having written the program that
found the solutions for me.

In my opinion you could have comunicated in advance what people can or cannot expect
from your site. Now for me personally some things came as a surprise.