The New Sudoku Players' Forum

[SarahJ]

Hey Guys,

Check this site out. It'll help everybody learn all the methods needed to know for solving. www.bestsudokusecrets.com

Happy Sudoku everyone

[Carcul]

Hi SarahJ.

Welcome to this forum.
Why would anyone spend money in buying that if one can probably learn more for free in this forum?

Carcul

[Havard]

Hi SarahJ and welcome to the forum!

I have this puzzle I have been struggling with a bit lately! I was wondering if you could give me some ideas for how to start with this puzzle, say, to show me how I should go about to place the 3-4 first numbers? I saw on your website that you are a sudoku-pro and I can't wait to get some professional advice on this one! If your advice is as good as I hope it is, I will purchase you book for sure! (and I am sure all the other member who read your solution-suggestion will purchase your book too!)

This is the puzzle in question. It was published in a newspaper in my "area" a little while back, but I can't seem to crack it! I even have trouble placing my second number...

Code: Select all

+-------+-------+-------+
| 1 . . | . . 7 | . 9 . |
| . 3 . | . 2 . | . . 8 |
| . . 9 | 6 . . | 5 . . |
+-------+-------+-------+
| . . 5 | 3 . . | 9 . . |
| . 1 . | . 8 . | . . 2 |
| 6 . . | . . 4 | . . . |
+-------+-------+-------+
| 3 . . | . . . | . 1 . |
| . 4 . | . . . | . . 7 |
| . . 7 | . . . | 3 . . |
+-------+-------+-------+


Can't wait for your reply!

Havard

[SarahJ]

Yes, I'll definitely solve it for you. I'm at work right now but will take a look when I get home tonite.

[andrewd]

Hi,

I await Sarah's solution with interest. In the meantime, could Harvard please tell me the name of the newspaper it came from? Just so that I don't pick it up (which I normally do for the Sudoku puzzle) if I find a copy on any part of the London Transport network.

Thanks

Andrew D

[tarek]

Don't worry, I suspect that it came from a very cold part of FINLAND

if a non Finnish puzzle is required, I suggest one of my fluid drives or ultimaltely Ocean's most recent diamond

tarek

[udosuk]

Don't worry, I suspect that it came from a very cold part of FINLAND

Either that, or Norway (where Havard's from) or Sweden...

These Nordic folks are certainly in a different class from the rest of us... Keep an eye on the competitors from Scandinavia in the upcoming World Sudoku Championship!

Meanwhile, we're all eagerly looking forward to Sarah's reply...

[merallas]

I offer SarahJ the program below free of charge.

http://homepages.ipact.nl/~allersma/all_lab.htm#soft

However some manual help is needed. So if you place a 6 and a 2 at the right location the puzzle become very simple.

[Len]

This puzzle required me to find eight numbers by trial and error to solve. The most I ever experienced before was 5. I can't believe I found these numbers so fast on my spreadsheet so I'm going to have to reverse my search algorithm and check for multiple solutions:

160/007/490
534/120/608
709/600/500

405/300/900
010/080/002
600/004/000

300/000/010
040/000/007
007/000/300

So I reversed the search algorithm and only needed 5 additional numbers to solve:

100/007/090
030/020/008
009/600/500

005/300/900
013/080/002
608/004/100

306/000/010
040/000/067
007/000/300

This yields the same solution, so I presume it is unique.

The one posted below by unkx80 was a real bear. It required finding 5 numbers for the forward algorithm and 6 for the reverse but the solutions were the same. I run the algorithms manually, so this method would be much slower than a program.

[merallas]

Ok, the 6 is now in the right location. If you find the 2 the puzzle can be solved using naked single, naked pair or single cell.

[unkx80]

I offer SahraJ the program below free of charge.

http://homepages.ipact.nl/~allersma/all_lab.htm#soft

On your page you ask for people to send sudokus your program cannot solve. Here is one, taken from http://diuf.unifr.ch/people/juillera/Sudoku/InterestingSudokus.html (last one in "Beyond Forcing Chains")

Code: Select all

000001002
010020030
400500000
004000006
070030010
800000900
500008000
000010070
006400500

Your program output is:

Code: Select all

random method not possible; hit key to stop

[merallas]

Hello unkx80,

Because there is only one cell with two possibilities this sudoku requires some additional handwork. So if you make e.g. r9c9=9 the program will solve the puzzle. It is quite easy to find this by trial and error. In the future I will expand the program by a routine which test the possibilities of each cell one by one in cases of sudoku like this one.

[QBasicMac]

This puzzle required me to find eight numbers by trial and error to solve.

Me, too. I use a program I wrote in QBasic. It reported only one solution, while exhausting all possible guesses.

Took about 10 seconds. Evidently not as fast as your spreadsheet.

Mac

[merallas]

Hi unkx80,
In the mean time I have added more powerfull routines to solve difficult (almost impossible) sudokus. Some patient is required in some cases. So I invite you to find again a sudoku which cannot be solved by my program.

By the way, thanks for the link to "InterestingSudokus". It is a very nice overview of the sollution methods.

regards,
Merallas

[udosuk]

Merallas, check out this thread, if your program could solve the bulk of those puzzles I'd say it's very close to being complete...