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Sep 18. 2005

 
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Boweasel
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PostPosted: Sat Jan 28, 2006 10:54 pm    Post subject: Sep 18. 2005 Reply with quote

I've experienced little difficulty in solving the puzzles designated 'very hard' in the last several weeks, and since I'm a relative newcomer to the game and the website, I thought I'd start working on some of the archived 'very hard's...

Sep 18 2005 has me completely stumped unless I resort to guessing. I read nothing in the forum archives about anyone having any difficulty with this puzzle, so I can only infer that I'm simply not seeing something that everybody else managed to see. Could someone please tell me what it is? Or have I made some grievous error in getting to this point?

9 4/7 6/7 1/5 8 3 1/4 5/6 2
1 2/4 5 6 2/4 9 3 7/8 7/8
2/6 8 3 1/2/5 2/4/5 7 1/4 5/6 9
7 5 4 3 9 8 6 2 1
3 1/2 1/2 4/7 6/7 4/6 8 9 5
8 6 9 2/5 2/5 1 7 3 4
5 9 1/6/7 8 3 4/6 2 1/4 6/7
2/6 1/2/7 1/2/6/7/8 4/7 6/7 5 9 1/4 3
4 3 6/7/8 9 1 2 5 7/8 6/7/8

Bo

PS Apparently I also don't know how to properly enter a matrix. It looked perfectly aligned when I entered it, but when I hit the 'preview' button, the matrix lost all of it's spacing. So that prompts another question... What am I doing wrong in entering a matrix?[list=][/list]
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alanr555



Joined: 01 Aug 2005
Posts: 193
Location: Bideford Devon EX39

PostPosted: Sun Jan 29, 2006 12:32 am    Post subject: Re: Sep 18. 2005 Reply with quote

Code:

  9    4/7          6/7      1/5       8       3   1/4   5/6      2
  1    2/4            5         6       2/4     9     3    7/8    7/8
2/6    8              3      1/2/5  2/4/5    7   1/4   5/6      9
  7     5              4         3        9       8     6     2        1
  3    1/2          1/2      4/7     6/7    4/6    8     9        5
  8     6              9       2/5     2/5      1     7     3        4
  5     9           1/6/7      8        3     4/6    2    1/4     6/7
2/6  1/2/7   1/2/6/7/8  4/7     6/7      5     9    1/4      3
  4     3           6/7/8      9        1       2     5    7/8    6/7/8   

PS  Apparently I also don't know how to properly enter a matrix.  It looked perfectly aligned when I entered it, but when I hit the 'preview' button, the matrix lost all of it's spacing.  So that prompts another question...  What am I doing wrong in entering a matrix?

It is necessary to surround a message with the code and /code
marks. Unfortunately the system does not default to setting them
(despite their value in nearly all situations!) and so one has to place
them individually. There is also a defect in the system in that the
space for typing messages allows more characters per line than
the space which formats the messages for presentation. Thus it
is necessary to write the message leaving space at the right end.

Alan Rayner  BS23 2QT
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alanr555



Joined: 01 Aug 2005
Posts: 193
Location: Bideford Devon EX39

PostPosted: Sun Jan 29, 2006 12:41 am    Post subject: Re: Sep 18. 2005 Reply with quote

Code:

> Sep 18 2005 has me completely stumped unless I resort to
> guessing.  I read nothing in the forum archives about anyone
> having any difficulty with this puzzle.

> Have I made some grievous error in getting to this point?

  9    4/7          6/7      1/5       8       3   1/4   5/6      2
  1    2/4            5         6       2/4     9     3    7/8    7/8
2/6    8              3      1/2/5  2/4/5    7   1/4   5/6      9
  7     5              4         3        9       8     6     2        1
  3    1/2          1/2      4/7     6/7    4/6    8     9        5
  8     6              9       2/5     2/5      1     7     3        4
  5     9           1/6/7      8        3     4/6    2    1/4     6/7
2/6  1/2/7   1/2/6/7/8  4/7     6/7      5     9    1/4      3
  4     3           6/7/8      9        1       2     5    7/8    6/7/8   

+++

I have found my sheet for this puzzle and I can confirm that
the solution for each unresolved cell is contained within the
candidate profiles shewn. Several of them have the same
profiles as I have on my sheet. Thus there is no immediate
evidence of an error so far. However, I would need to rework
the puzzle to make any further comment.

Apart from that I can confirm that this puzzle is one where it
was necessary to switch from Mandatory Pairs to Candidate
Profiles in order to reach a full resolution.

Alan Rayner  BS23 2QT

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alanr555



Joined: 01 Aug 2005
Posts: 193
Location: Bideford Devon EX39

PostPosted: Sun Jan 29, 2006 2:50 am    Post subject: Re: Sep 18. 2005 Reply with quote

Code:

  9    4/7          6/7      1/5       8       3   1/4   5/6      2
  1    2/4            5         6       2/4     9     3    7/8    7/8
2/6    8              3      1/2/5  2/4/5    7   1/4   5/6      9
  7     5              4         3        9       8     6     2        1
  3    1/2          1/2      4/7     6/7    4/6    8     9        5
  8     6              9       2/5     2/5      1     7     3        4
  5     9           1/6/7      8        3     4/6    2    1/4     6/7
2/6  1/2/7   1/2/6/7/8  4/7     6/7      5     9    1/4      3
  4     3           6/7/8      9        1       2     5    7/8    6/7/8   

a) Row 8:  r8c3 is Sole Position for the 8
b) Col 3:  Remove the 8 from r9c3
c) Note 67 pair between r1c3 and r9c3
d) Remove 67 from r7c3 - leaving 1 as Sole Candidate
e) Proceed with consequent eliminations.

Alan Rayner  BS23 2QT

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Boweasel
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PostPosted: Sun Jan 29, 2006 5:12 am    Post subject: Reply with quote

Thanks for the tips on entering the matrices properly. Hopefully I'll never have to do it again....

We went out for dinner after I posted the message, and when I got home I picked up my paper with the matrix and all it's possible cell values. The '8' practically jumped out of the page in it's desire to be seen, so I logged back on hoping no one had responded to my message.

Too late...

But boy, is it ever easy to miss something like that.

Thanks anyway, and I apologize for wasting anyone's time on a visual error.

Bo
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Peter A
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PostPosted: Tue Jan 31, 2006 12:36 pm    Post subject: Sept 18, 2005 Reply with quote

Bo
I reached the same position as you - seeming to indicate that we are right. I too could find no simple logical next step. Possibly, making an assumption and seeing if it works [= guesswork?!] is a valid approach.

However, I chose to start with R7C6 (currently {4/6}. Strangely, both values eventually led to a logical impasse...

Peter
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Peter A
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PostPosted: Tue Jan 31, 2006 12:40 pm    Post subject: Oops Reply with quote

Just saw previous posts. Red face here.
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Just_Curious
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PostPosted: Tue Jan 31, 2006 7:56 pm    Post subject: Reply with quote

How long does it take to solve a sudoku 9x9 puzzle ?
Easy Level = ??
Medium level ??
Hard level ??
Very Hard Level ??

Thanks,

Just curious
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