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Nov 4 VH

 
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Nov 04, 2008 12:32 am    Post subject: Nov 4 VH Reply with quote

OK, what am I missing? There must be a hidden pair or something in there, but I can't see it. All my usual approaches have failed.

Code:

+-----------------+--------+-----------------+
| 3     479  46   | 5 2  1 | 48   4679  468  |
| 2456  245  1246 | 7 9  8 | 1345 13456 1346 |
| 57    8    19   | 6 4  3 | 159  2     17   |
+-----------------+--------+-----------------+
| 9     6    5    | 3 18 2 | 7    14    148  |
| 1     34   348  | 9 7  6 | 358  35    2    |
| 28    23   7    | 4 18 5 | 6    13    9    |
+-----------------+--------+-----------------+
| 67    1    369  | 2 5  4 | 39   8     367  |
| 24568 2457 2468 | 1 3  9 | 24   467   46   |
| 24    2349 234  | 8 6  7 | 1234 1349  5    |
+-----------------+--------+-----------------+


Cheers,
kragzy
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crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Tue Nov 04, 2008 2:06 am    Post subject: Re: Nov 4 VH Reply with quote

kragzy wrote:
OK, what am I missing? There must be a hidden pair or something in there, but I can't see it. All my usual approaches have failed.

Code:

+-----------------+--------+-----------------+
| 3     479  46   | 5 2  1 | 48   4679  468  |
| 2456  245  1246 | 7 9  8 | 1345 13456 1346 |
| 57    8    19   | 6 4  3 | 159  2     17   |
+-----------------+--------+-----------------+
| 9     6    5    | 3 18 2 | 7    14    148  |
| 1     34   348  | 9 7  6 | 358  35    2    |
| 28    23   7    | 4 18 5 | 6    13    9    |
+-----------------+--------+-----------------+
| 67    1    369  | 2 5  4 | 39   8     367  |
| 24568 2457 2468 | 1 3  9 | 24   467   46   |
| 24    2349 234  | 8 6  7 | 1234 1349  5    |
+-----------------+--------+-----------------+

Hint:>>> Try a naked triple

I thought this was a toughie too. See hint above.


Last edited by crunched on Tue Nov 04, 2008 2:10 am; edited 1 time in total
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Tue Nov 04, 2008 2:10 am    Post subject: Re: Nov 4 VH Reply with quote

kragzy wrote:
OK, what am I missing? There must be a hidden pair or something in there, but I can't see it. All my usual approaches have failed.

There's a Naked Triple/Hidden Pair in [r1]. After that, an (XY-Wing) cracks the puzzle.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Nov 04, 2008 4:31 am    Post subject: Reply with quote

Ahhhhhhhh, 468. I knew it had to be in there somewhere.

Many thanks.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Tue Nov 04, 2008 6:56 am    Post subject: Reply with quote

After the x-wings in 7 (rows 3 and 7) and 9 (also rows 3 and 7),
an xy-wing 19-17-79 in row 3 / box 3.
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sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Tue Nov 04, 2008 12:35 pm    Post subject: Reply with quote

This one was for me unusual in that I came across two X-wings whilst still filling in candidates. And these two X-wings proved to be enough (indeed on 7 and 9).

Peter
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Tue Nov 04, 2008 8:45 pm    Post subject: Reply with quote

sdq_pete wrote:
these two X-wings proved to be enough (indeed on 7 and 9).


Peter,

you must have done some more magic ...
After basics and the x-wings, this is where something else is needed (e.g. the xy-wing)

Code:

+--------------------------+--------------------------+--------------------------+
| 3       79      46       | 5       2       1        | 48      79      468      |
| 2456    245     1246     | 7       9       8        | 1345    13456   1346     |
| 57      8       19       | 6       4       3        | 159     2       17       |
+--------------------------+--------------------------+--------------------------+
| 9       6       5        | 3       18      2        | 7       14      148      |
| 1       34      348      | 9       7       6        | 358     35      2        |
| 28      23      7        | 4       18      5        | 6       13      9        |
+--------------------------+--------------------------+--------------------------+
| 67      1       369      | 2       5       4        | 39      8       367      |
| 24568   2457    2468     | 1       3       9        | 24      467     46       |
| 24      2349    234      | 8       6       7        | 1234    1349    5        |
+--------------------------+--------------------------+--------------------------+
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Tue Nov 04, 2008 10:18 pm    Post subject: Reply with quote

This is the way the "Very Hards" should be. I used x-wings which perhaps weren't needed - and finished off with an xy wing.
The thing is - I enjoyed doing it - no obvious one step solutions - and no Methulsa transported chains or whatever.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Wed Nov 05, 2008 2:18 am    Post subject: Reply with quote

cgordon wrote:
This is the way the "Very Hards" should be. I used x-wings which perhaps weren't needed - and finished off with an xy wing.
The thing is - I enjoyed doing it - no obvious one step solutions - and no Methulsa transported chains or whatever.


Well, then, this will be right up your alley:

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=14081

Keith
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Wed Nov 05, 2008 2:55 pm    Post subject: Reply with quote

Quote:
Well, then, this will be right up your alley:
http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=14081
Keith


Definitely up my alley! Difficult but not dangerous. Highly recommended for those waiting for their next “very hard”.
Craig
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Wed Nov 05, 2008 3:14 pm    Post subject: nothing more complicated ? Reply with quote

cgordon wrote:
This is the way the "Very Hards" should be. I used x-wings which perhaps weren't needed - and finished off with an xy wing.
The thing is - I enjoyed doing it - no obvious one step solutions - and no Methulsa transported chains or whatever.


Shortly before I spotted the X wings (as described by Nataraj) I had achieved the same resulat in a far more complicated way Er in Box 1 and the strong links in 7 and 9 created the eliminations adequate to reveal the XY wing. So why do it simply when there is a more complex way of do it?!
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sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Sat Nov 08, 2008 12:04 pm    Post subject: Reply with quote

nataraj wrote:

Peter,

you must have done some more magic ...


I finally found time to look at it again; anyhow, I don't know how I did it before Confused It frequently seems to happen in this forum that someone reports solving a puzzle without "advanced techniques" - to find the feat non-repeatable. It's a bit like discovering cold fusion I suppose - hmmm... how did I do it?

Peter
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