OK - Ask me a Sudoku Question!

I created a program that will generate a
word sudoku board based on the word you type in
and that word will be spelled out in the middle
of the board. I call LP Maker.
Does this sounds program like people will pay $$$ for?

There is an error in the Jan/01/2008 sudoka game.
The first row and the fifth column contain all of the candidates for ssquare 1,5(xy-coordiates) of the top row. No solution is possible.

Hi, I keep getting "You are not allowed", every time I try loading this site. I got into the Forum through my E-mail link but I can't get Home page. It keeps telling me Error: http,401,2. Please help me sa I love this site.

Me again, now when I try to get on the site its telling me 'Server error '/' Application' and I do know my User name and password but i can't even load the site. You might need to check with your server, my son says there might be a Virus on this site.

Hi Gath,
I cannot get to the sudoku puzzles. Each time I try I get a page that tells me that I am not authorized to view this site!!!
Any clues?

I too was getting the messages you guys were, but today it changed to something about a code problem or some such. My guess is Gath is working out the kinks.
Yours in withdrawal,
Terry

Glad I'm not the only one suffering "Sudoku Withdrawal"
I now get the same Server Error message as Zoki.
I sent Gath a message on the info email but it was returned by the postmaster.

My last error message was pretty cute, because it was trying to help me isolate the problem. It i.d.'d a line of code ("D = cljha;lhjgfdophedh" or some suce, then gave me about 10 lines of code where the solution probably was. Since the most complicated thing I do to fix problems is find the right phone number for the proper technician (Microsoft, Comcast, or Craig my local computer genius) and then follow instructions (Them: "Go to 'My Settings' and click on X." Me: "I'm sorry. Where is 'My Settings?'") My next computer will be a Mac, as compact and wireless as I can get it. Then I would have a tower burning party but for some environmental issue, so I'll have to settle for dumping it at my recycling center as I hum the Toreador song from Carmen. Which is all by way of saying thank goodness for young geniuses like Gath!

Hi, I'm brand new to sudoku, is there anywhere I can read about the theory behind it or learn how to do it??? Please & thanks

Welcome, blue. Look at the top right of this page, and click on the blue link to "Final page of tough of November ...." On that page, on the right side, are links to prior posts. Go to the bottom of that list, and the postings start with beginner basics. Very good explanations. Have fun!!!

I'm looking for someone who has played Redz Sudoku and might be able to help me with problem 279 of the Sand Storm version.

Redz from www.TAMSA.org, that is.

I have a puzzle in the paper this morning that I got stuck on. I finally just guessed and completed the puzzle but would like to see how an expert would handle this particular puzzle.
638 519 -4-
--4 263 -98
2-9 874 -63
-4- 7-6 31-
-9- 3-2 -56
3-6 1-5 -8-
-6- 438 921
483 921 675
9-- 657 834

On the harder puzzles, I often get to this point and just end up staring at it without a clue how to solve it.

Hi Dave!
You have solved quite a bit of that puzzle! It is almost unusual that one would require an advanced technique at this stage.

There are a number of things you can do. I will post just one. First, I will label the grid as follows: columns are a through i left to right. Rows are 1 to 9 bottom to top. (Like algebraic chess board notation.) Thus the bottom left cell is a1. Top right corner is i9.
1) A standard technique called an xy wing. Sometimes it is just called a Y wing. If you were to fill in the possibilities, - also called pencil marks - just the remaining possible entries for each cell, then:
cell c3 is limited to 57, cell c6 is limited to 25, cell b4 is limited to 27.
Suppose cell c3 is 7, then c5 is not 7. Suppose cell c3 is 5, then cell c6 is not 5 but 2, then cell b4 is not 2 but 7. Again, cell c5 is not 7. Thus, we can safely remove 7 from c5. The only remaining possibility at c5 is 1. That should unlock the puzzle for you.

BTW, I host a sudoku blog at this site. The link is in the upper right hand corner, under "check out the sudoku blog". If you click on the link, the right hand column of the page will be filled with previous blog entries. Some of the earlier ones describe many techniques to tackle truly difficult puzzles. Some of the later ones tackle even more difficult puzzles. Many puzzle solutions are illustrated from start to finish. A bit of work is required to interpret the meaning of my writings. Sorry about that. Some day I will update the blog to reflect current terminology.

Hi Dave again!
To shorten the logic and also present more complex steps, the ywing above could be written as:
(7=5)c3-(5=2)c6-(2=7)d4 => c5<>7
I formally used ==, now use = to mean logical OR. At least one of (7,5) can exist at that cell.
I formally used --, now use - to mean nand. At most one of c3,c6 can be 5. This chain is called a forbidding chain in the early blog stages, and later is called an alternating inference chain - as that is what the most of the sudoku world calls it. The early terminology came from Bruno Greco, who no longer posts here. The later terminolgy is a reflection of me trying to conform to other sudoku sites. However, grid representations are largely non-standard.

Here is a link to gb's work on forbidding chains:
http://brunogreco.free.fr/bazar/sudoku/forbidding%20chains1.htm

Steve ... Thank you. I see how you did that. Let me ask you one more question. Did you randomly find those three or did you search thru the rest of the puzzle first? I just had another one and tried to find the solution the same way and was unable to and resorted to doing a semi-guess, either or check which showed me the incorrect guess and the correct guess. In other words, I got down to the possibilities or pencil marks and then filled in one number and the other number side by side in the two posssibilities squares and found the solution.

Dave, after much practice, certain patterns become easier to find. Much like a pair is easy to spot, after some considerable time Y Wings can be easy to spot. The longer the chain, I think the harder to find (generally, not always).

BTW, a well chosen examination of both alternatives in a cell is often the quickest way to unlock a tough puzzle. Learning to spot the patterns is much work. It has the advantage of not feeling like a guess. It has the further advantage of reinforcing the patterns better, imo.

Steve ... I was thinking that was going to be your answer. Thank you so much for your help. This may help me take it to the next level. Now that I am back home in Oregon, my local paper has more difficult puzzles on Fri. and Sat. and the USA Today always has more difficult puzzles later in the week. I have been able to solve the Hard ones here without too much difficulty but sometimes I just give up on the tough. Thanks again.

Could someone suggest where (on the web) I can find a good basic primer on tips, tricks, techniques, etc. for solving sodoku puzzles?
Thanks.

Hi Gath,

The Sudoku below I cannot solve - and I have been trying since it was published. It was in a reputable UK newspaper in August 2005, and compiled by a reputable Sudoku expert. Can you give me any clues on how to solve it - using logic. Many Thanks, and ...

Best Regards,

Neil
~
080509000
590003700
000070000
760000800
100000004
009000037
000010000
004300086
000708050

Gath,
My question is not about solving Sudoku puzzles. It's about membership, but I couldn't see where else to send you a message.
My membership is coming up for it's first renewal on 6 June. I originally paid by cheque which I posted to you via an address which was available as I signed up. Did not keep address and want to get the cheque to you and cleared by 6/6. Could you please let me know the address and who to make the cheque out to?
Thank you for this wonderful site - my life has changed because of it. Cynthia

Hi CynB,

The cheque info can be found here:
http://sudoku.com.au/UserDetails.aspx?t=tell

If you would like to get in touch with me, you can use the 'Contact Us' link at the top of every page. Or else search for me in the members section.

Hope that helps . Thanks to Angie for letting me know about this question.


Gath

Hello I am totally knew to Sudoku and I have a sudoku for dummies and it is beyond my feeble understanding I dont know why I cannot figure it out I want to learn something new to use my brain but I am lost :( I dont mean to bother you. you are necessary thank you so much

Hi, I don't get the "grey" or the "highlight" cells. All other colors seem fine. Suggestions? I haven't had a computer for months and have really missed everyone, glad to be back! ♥ PJ

Hi Gath,

Many of the (useful, and sometimes wonderful and/or elegant and/or extremely sophisticated) solutions on these pages refer to 'basic techniques' - I would be pleased if you could advise what these 'basic techniques' are. Many thanks.

Best regards, Neil

PS: I thought that I understood what these 'basic techniques' are, but there seem to be variations - depending on who suggested them (in the Tough pages - which are the only ones that I look at).

Hi, fairly new to this site, have relied upon local newspaper to get my daily fix but have moved and new paper doesn't have a puzzle!
Have managed a couple of toughs but get stuck most of the time, have tried to fathom the paths that people post but get always have to skip "Start 22, UP 26" (for eg) as haven't a clue what this means, can anybody pls help this poor peabrain?

sokay, got it

How do I retrieve a "saved game"? I'm using Windows Vista, and I'm told the game will be saved as a cookie, but when I check my cookies, I can't identify the one I'm looking for. Thanks for any help you can give.

Hi Gath,
How do I retrieve a "saved game" puzzle? I'm told it will be saved as a cookie, but I can't identify it from my list of cookies on Windows Vista. Any suggestions?

Thanks,
Charlie

I finally figured it out - and in case someone else is having the same problem: On the game page, select the correct date of the puzzle you saved, then the same difficulty, and click on "Load Game". Puzzle appears!

Hi, everyone! Is there a way I can solve the following problem on this site?
Many a times, we fill in the blank cells with different possibilities, particularly for the Tough category puzzles. We then get stuck and would like to save the puzzle with the UPs/ cells filled with different possibilities, to be tackled the next day. It is a big job to start from scratch, filling in the cells once again,after we log out and shut the computer for the night. Besides manually copying the filled cells on a piece of paper and retyping these the next time we want to try for a solution, wouldn't it be nice if we could recall our previous day's work from a saved page?
I am sure some others would have had a similar experience. How did they overcome this?
I would welcome e mails from anyone who has a workable answer to this.
Thanks.

hello, I tried to download a video off you tube but cannot see an embed code where do I find this, there is a copy and paste link but that doesnt work when i paste it into the spot for you tube just comes up your youtube cannot be found, thanks sophia

Gath,

Is the tough of Dec 23 solvable or not?

How to make a sudoku puzzle by your own?
and also
How to increase your speed in solving?

Please answer, thank you

Anyone have a solution they would like to share for the tough of Dec 23, 2008?

Re the Dec 23 Tough: Thanks for the company, Dave. I, too, would like to see a solution, or at least some comments, there.. . . so I could at least let go of it and get on with my life ! :-)

I have posted a solution to the Dec 23 Tough.

Gath Why can't I find the cookbook Jane keeps talking about? I can't find anything that says links. It not really important, but I would like to know

I cannot logically solve the 30-1-2010 Tough Sudoku puzzle from this site. Have solved to a certain point, then can see no other eliminations. Surely there is a way to do it without trial-and-error. I would certainly appreciate any guidance.