Lost in Sudoku land

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Lost in Sudoku land

Postby pmsmith » Wed Dec 12, 2007 4:07 pm

Hi,
I was reading a post by somebody requesting help on a puzzle and now can't remember where it was posted. I might have transcribed it a little incorrectly but ...

091000004
425809030
068350000
070000000
004000000
000000000
000000400
000000000
000080090


The person who posted it used "*" for my zeros and used a forward slash to separate cells along each line.
eg for r1 *91/***/**4

Can anyone locate this puzzle or it's author?

Thank You

Peter
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Lost in Sudoku land

Postby pmsmith » Wed Dec 12, 2007 10:00 pm

Ok,
I managed to locate the post in "Pappacom papers" under a user called "ilquerceto".

Now I have to try and solve it!

Peter:D
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Re: Lost in Sudoku land

Postby daj95376 » Wed Dec 12, 2007 10:54 pm

pmsmith wrote:Now I have to try and solve it!

That shouldn't be too hard. It has many, many solutions for you to choose from!!!
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Re: Lost in Sudoku land

Postby pmsmith » Thu Dec 13, 2007 12:42 am

Ok,

Are you saying this puzzle is basically a joke and the problem is under-specified.?

Peter:(
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Re: Lost in Sudoku land

Postby daj95376 » Thu Dec 13, 2007 1:15 am

pmsmith wrote:Ok,

Are you saying this puzzle is basically a joke and the problem is under-specified.?

I'm saying that the puzzle has multiple solutions and that most people would consider it an invalid Sudoku puzzle. When it was originally posted, the poster included a 'progress' grid showing where he'd reached in solving the puzzle. By then, only one solution remained and udosuk posted a reply on how to complete the puzzle. Now you know why many people in the forum request the original puzzle be included, and why they start from there on solving it.
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Re: Lost in Sudoku land

Postby stumble » Thu Dec 13, 2007 5:52 pm

I’ve been itching to discuss this puzzle from another angle.
I'm STILL trying to refine my AIC technique, as it seems simpler to me than some of the ‘fishy’ solutions you guys use. I’ve had some success but sometimes it STILL seems to mysteriously backfire on me:

This is the ilquerceto puzzle post:
http://forum.enjoysudoku.com/viewtopic.php?t=5364&view=next
Code: Select all
.---------------------.---------------------.---------------------.
| 3      9      1     | 67     67     2     | 8      5      4     |
| 4      2      5     | 8      1      9     | 7      3      6     |
| 7      6      8     | 3      5      4     | 9      12     12    |
:---------------------+---------------------+---------------------:
| 6      7      23    | 25     29     8     | 1235   4      1259  |
| 129    5      4     | 267    3      167   | 126    8      129   |
| 129    8      23    | 4      269    156   | 12356  126    7     |
:---------------------+---------------------+---------------------:
| 125*   13     6     | 9      27     357   | 4      127    8     |
| 8      13     9     | 2567   4      3567  | 1256   1267   125   |
| 25     4      7     | 1      8      56    | 256    9      3     |
'---------------------'---------------------'---------------------'

With locked ‘1’ candidates in box 3, r7c1<>1.
In the referenced post udosuk suggested eliminating ‘1’ candidates in box 6. Therefore I tried this Alternating Inference Chain (AIC)
Code: Select all
.---------------------.---------------------.---------------------.
| 3      9      1     | 67     67     2     | 8      5      4     |
| 4      2      5     | 8      1      9     | 7      3      6     |
| 7      6      8     | 3      5      4     | 9      12*    12*   |
:---------------------+---------------------+---------------------:
| 6      7      23    | 25     29     8     | 1235   4      259-1 |
| 129    5      4     | 267    3      167   | 126    8      29-1  |
| 129    8      23    | 4      269    156   | 12356  126    7     |
:---------------------+---------------------+---------------------:
| 25     13*    6     | 9      27     357   | 4      127*   8     |
| 8      13     9     | 2567   4      3567  | 1256   1267   25-1  |
| 25     4      7     | 1      8      56    | 256    9      3     |
'---------------------'---------------------'---------------------'

(1)r7c2=r7c8-r3c8=r3c9=>r458c9<>1
this does not agree with the solution, as r4c9=1 is the correct answer.
What did I do wrong?
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Re: Lost in Sudoku land

Postby daj95376 » Thu Dec 13, 2007 7:04 pm

stumble wrote:(1)r7c2=r7c8-r3c8=r3c9=>r458c9<>1
this does not agree with the solution, as r4c9=1 is the correct answer.
What did I do wrong?

Your single-digit AIC chain starts with [r7c2]= and ends with =[r3c9]. So far so good.

None of your elimination cells see both [r7c2] and [r3c9] -- not good!!!

I strongly recommend that you perform less difficult techniques first before trying to apply an AIC. If you need AIC practice, I'm sure that most people in the forum will be willing to provide a PM that's ready for a single-digit AIC elimination. Once you get proficient at them, then you can proceed to the more general AIC.
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Re: Lost in Sudoku land

Postby stumble » Thu Dec 13, 2007 7:27 pm

Ok thanks daj95376.
I DID know that. Somehow that basic rule dropped out of my head at some point. When I reviewed my rules for AIC while working the puzzle I hadn't made that crystal clear to myself. I'm embarrassed enough that I won't make that mistake again. But there'll be plenty of others. Please DO correct me when I post. It seems that's the only way I'll learn.
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