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hard sudoku by hand

 
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[M]ephisto

Joined: 12 Jan 2006
Posts: 3
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PostPosted: Thu Jan 12, 2006 5:09 pm    Post subject: hard sudoku by hand Reply with quote

I tried solving by hand one of the puzzles from the thread "What is the hardest known sudoku?"
This is the one I used:
Code:

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


This is as far as I could get...

Code:

   |---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 |     7 |  1589 |   586 ||  1269 | 13569 | 23569 ||     4 |   125 |   123
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r2 | 14569 |     2 |   456 ||  1469 |     7 | 34569 ||   156 |     8 |    13
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r3 |  1456 |   145 |     3 ||  1246 |   156 |     8 || 12567 |  1257 |     9
   |       |       |       ||       |       |       ||       |       |       
===========================||=======================||=======================
r4 |  2489 |  4789 |  2478 ||     5 |  1689 |   469 ||     3 |  1247 | 12478
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r5 |  3458 |     6 |  4578 ||   148 |     2 |    34 ||  1578 |     9 |  1478
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r6 |234589 |  4589 |     1 ||   489 |   389 |     7 ||   258 |   245 |     6
   |       |       |       ||       |       |       ||       |       |       
===========================||=======================||=======================
r7 | 12568 |  1578 | 25678 ||     3 |   568 |   256 ||     9 |  1247 | 12478
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r8 |  1258 |     3 |  2578 ||  2789 |     4 |   259 ||  1278 |     6 |  1278
   |       |       |       ||       |       |       ||       |       |       
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r9 |  2468 |   478 |     9 ||  2678 |    68 |     1 ||   278 |     3 |     5
   |       |       |       ||       |       |       ||       |       |       
-----------------------------------------------------------------------------


Can anyone help me solve this using techniques that a human can execute?
btw, I'm new here. Hi all!
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tarek

Joined: 31 Dec 2005
Posts: 153
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Location: London, UK

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PostPosted: Thu Jan 12, 2006 9:36 pm    Post subject: Reply with quote

That puzzle ( #77 from the top1465 ) apparantly can be solved using logic, however it is too complicated for humans. The mainstream techniques used by humans will fail to solve this.

This makes the DIABOLICAL look like an EASY.

Try solving it with the minimum number of guesses

good luck

tarek
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[M]ephisto

Joined: 12 Jan 2006
Posts: 3
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PostPosted: Sat Jan 14, 2006 9:13 am    Post subject: Reply with quote

tarek wrote:
"That puzzle ( #77 from the top1465 ) apparantly can be solved using logic...

What exactly is the technique used?
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Ruud
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Joined: 17 Sep 2005
Posts: 708
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Location: Netherlands

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PostPosted: Sat Jan 14, 2006 10:25 am    Post subject: Reply with quote

There are a couple of ways to solve these.

Please read the following topic on the players forum: http://www.sudoku.com/forums/viewtopic.php?t=2382

A variety of hi-tech solving methods is on display there.

Ruud.
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[M]ephisto

Joined: 12 Jan 2006
Posts: 3
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PostPosted: Tue Jan 17, 2006 5:25 pm    Post subject: Reply with quote

Man! I can't understand anything beyond chains! How do you guys come up with such incredible theories! How old are you guys? I'm 17.
Anyway, I started learning C this year and I created a little program to solve this puzzle a few days ago. I know nothing about creating a GUI and don't even know if its possible in C. I just used arrays, 'for' loops, printf and scanf statements! It does the job though. It takes a bit under 2 seconds to solve this puzzle and about a second to solve most others. Is that good? The sad thing is that it dosen't solve puzzles that have more than one solution.
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rkral

Joined: 21 Oct 2005
Posts: 233
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PostPosted: Tue Jan 17, 2006 8:12 pm    Post subject: Re: hard sudoku by hand Reply with quote

[M]ephisto wrote:
This is as far as I could get...

Code:

   |---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 |     7 |  1589 |   586 ||  1269 | 13569 | 23569 ||     4 |   125 |   123

From where did you get that format for the candidates? TIA, Ron

Hint: The line wrap you are likely seeing should be a clue as to why I'm asking.
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