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Tough Sudoku for 19/September/2005


Choose a number, and place it in the grid above.

  1 2 3 4 5 6 7 8 9
Check out the latest post in the Sudoku Forum

Sudoku Solving Techniques

Submitted by: sudoku lover

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hi GG
see tips to set the solution by reasoning on
Have fun
Yes, gb, and thanx again...
I entered that comment yesterday, before you and pk gave me directions where to look...
13:17 Guessed at 3 spots.
26:00 - Fastest ever.
What exactly is X wing?
I tried it (the way I think it goes, but I don't understand reasoning behind it), however it didn't work in one case. Are the numbers on one side allowed to be in the same block, or does it have to be different blocks?
can always do all levels in less than 5 min. using cheat of not allowing incorrect moves
No, jc!

You can do all levels in less than 5 seconds:
- do 'show solution'
- take a number out
- put the same number in again

and presto! (or bingo, if you prefer...)
First tough one I've solved. Don't like to think how many turns it took. First time I've used X-wing technique - I still don't understand the logic of it but it seemed to work?!?
nice snowman...
sorry...6 mins 30 secs so proud.......only been playin for 3 weeks
Is anybody going to answer BW from Perth and explain what 'x wing' is? Keen to know also.
For people interested to learn X-wing and other solving tricks, check this out:
yay. so happy. pb of 18:54. x]
is a downloadable program which makes understanding the techniques much easier - if you are stuck you can use the 'hint' button and it explains the technique you can use.
New pictures!!!!!!!
18:03 for Tough - happy with that... no guessing required
Absolutely no guessing required. No X-wing required. This site is great!
Finished in 7:00 exactly. First Tough with no guessing. Thanks to some of you who have posted links to sites that explain the mathmatical theory behind certain techniques like the X wing and others. Anybody faster today?
27:45 ug, i had to guess once on this. i usually don't do these tough ones because i have trouble doing the whole thing without guessing
an undo button would be nice.
I won't build a snowman while I'm in Madrid...
Again to solve this puzzle with logic (no guesses), I had to use the fact that the solution is unique (2nd time using the 'unique' logic) - this still seems like 'cheating' to me.
5.27 Getting better
27:03 I had to use check moves twice. Yes, what is 'x-wing'?
Hi, Steve
This has already been discussed here. My opinion is that the problem we face is : 'How many solutions has this puzzle?', the answer, often being 'one and only one', has to be proven. And not 'Fill the grid with every number appearing etc, knowing that the solution is unique' which would be another puzzle. So, the proof of unique solution can't use... uniqueness of solution!!!
got stuck realised from gb website that I had missed an easy elimination - thanx gb - time of 17:45 not really valid because I paused time while I check gb site
That X wing thing is insane! It knid of feels like cheating though because I don't understand why it works. Perhaps I'll look into it...
Try unchecking 'Automatically remove Possibilities' AND checking 'Allow
incorrect Moves', also, never click on
'Check Moves'
All x-wing does is eliminate other possibilities by identifying two digits in given rows and columns that are interchangeable only with each other. Some people say on some Sudoku's that you must guess at some stage but if there is always only one solution you should never need to guess if you can visualise enough moves into the future. Agree?
wow, I don't care how good some of you guys are but to finally solve a tough without guessing sure feels good!!
You guys are so fast. It takes me longer to fill in all the 'possibilities' than it does for you to solve the puzzle.
Mar. 6, 2007.
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