Sudoku Puzzles

16.38 They're getting harder and harder, but I'm too addictedto stop!

10:23, and i only guessed 3 numbers...

07:24 Help me! I'm a sudokuholic... :-)!

Tough puzzle in 3:45.
Is Tough supposed to he more difficult than Hard??

I love this website especially the great sudoku puzzles!!!

About 12 mins but I mucked up my time because I paused to answer the phone and forgot to press 'start' again for a few moves. Would be useful if the time automatically re-started once you enter a number

nice picture.easier than ever before.thanks to GB

6:32, easier than a hard??

I can't do the tough ones without guessing! HELP

Sory to ask.

But how to solve this without gessing. I try to put this puzzle in a 'solver' and it didn't find any more logical steps. And still left a lot of numbers. It must exist more tricks.

Thanks

13:31 thanks for the wake up. now i can go about my day after doing these puzzles.

this web sight just gets better and better...can we have a tougher one? I'm getting too good.

Tough was rather easy today. 4:11 was my time and only had to guess once which thankfully was the right guess.

27:34 Slow but I did it without any guesses!!!

As a mathematician by trade, I am only satisfied with a solution if I can prove its uniqueness. And my quess is, the solutions involving 'guessing' do not establish uniqueness. For most of the toughs including today's I am unable to do this. I am really curious to know how these puzzles are generated, and is the uniqueness guaranteed by the algorithm?

9:43... even better than hard which was better than medium. I love the reward... Hope I could be there

To Andrei: I hear you about wanting to be able to fully justify each answer. I finally noticed the 'save game' feature yesterday, which helps when the simple logic runs dry. What I do is save the board when I run out of easy answers and then break up a pair to see what happens. If I find I'm on the wrong track, I load the board and go the other way. Rest assured the boards are unique.

Andrei: i did today's puzzle without guessing. for those that require guessing, a simple brute force checker can easily prove uniqueness, although you can prove it yourself following JL's advice.

I too hit a point where when I used a solver to get a hint I was told that the puzzle was either not solvable by logic alone or had more than one solution. Ugh. This happened after I correctly filled in 8 squares and confirmed they were correct.

Not bad at all. Once you pop you just can't stop...

I won't cry foul on those who solve the puzzles so quickly, but the tough ones do take a while for me. Probably why I like them so much. I like the reward for finishing the puzzle today. New feature?

Had to guess twice, I can't understand how some of you can figure it out with out quessing. There must be some tricks that I haven't learned yet.

Took a while this morning - can anyone tell me what city is shown in the photo.

this site is the best. good work and thank you.

Being a mathemetician will only help you in terms fo logic.

These are not math problems, they are logic problems.

And yes, the tough ones do require guessing sometimes at one stage or another.

Anestis.

Great site! How about making different shapes within the outer square? Rectangles? 'T'?

Never have to guess - there is always a logic sequence to solve

'Guessing' isn't required if an action has consequences that eventually lead to a paradox, then you can successfully eliminate it from consideration.

I usually can't see that far ahead, and so it is a true guess, but for those who can juggle that much in the head easily, more power to you.

3:53. Guessed one number.

Thanks for all the enhancements!

I am addicted. Have not slept for a long time.

27:54 is that a record?

How do all of you do this so quickly? I do it without any help. Do you get help from the allow correct moves box?

My mistake. I actually did it in 1 second:)

Am i the only one who finds the puzzles don't print well?

andrei :
every tough puzzle i tested here had unique solution, which proof it's a challenge to explain without brutally computing variants. Up to now i've more or less succeeded in that, ie if a variant needs to be studied, it's possible to do so visually, without saving, testing till More...

Can one go into details on this comment section for this puzzle?
If so, what should my next logical move be?

2** *6* 7**
*** *** *3*
*35 8*9 ***
37* *** 49*
*** *3* ***
*86 *9* 31*
*** 214 8*3
*1* *** ***
**3 95* 1*6
More...

Chris:
Using [row, column]

Where row 1 is on top, row 9 on bottom, column 1 on left, column 9 on right.

And where row 9 has possibility values of:
78, 24, 3, 9, 5, 78, 1, 24, 6

Chris (cont):
You can eliminate the possibility of 7 in [9, 1] because if you make that cell = 7 then
[9, 6]=8 making [8, 5]=7. This means that [2, 5] and [3, 5] cannot be 7.

Furthermore, if [9, 1]=7 then [2, 1] and [3, 1] cannot be 7 thus making [2, 3]=7. That means that [2, 4] and More...

Thanks for your response, Laura. But I think you are ahead of me! My line 9 which did not print, is different to yours.
478,24,3,9,5,78,1,247,6 so I do not have a pair of 78's to work with. I guess we must have the same puzzle at different stages of solution?