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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Fri Aug 29, 2008 6:09 am Post subject: Aug 29 vh |
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After basics,
| Code: |
+--------------------------+--------------------------+--------------------------+
| 6 29 5 | 3 29 1 | 8 4 7 |
| 49 34 8 | 7 6 5 | 39 1 2 |
| 129 7 123 | 4 29 8 | 39 6 5 |
+--------------------------+--------------------------+--------------------------+
| 3 6 4 | 1 7 29 | 5 289 89 |
| 5 29 27 | 8 3 6 | 1 279 4 |
| 129 8 127 | 5 4 29 | 6 279 3 |
+--------------------------+--------------------------+--------------------------+
| 7 1 23 | 9 8 34 | 24 5 6 |
| 48 5 6 | 2 1 34 | 7 389 89 |
| 248 34 9 | 6 5 7 | 24 38 1 |
+--------------------------+--------------------------+--------------------------+
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xy-wings (24-34-23-24 boxes 7 and 9)
There is a UR 89 with strong links:
strong link (9) in r8c89 means r4c8<>8 which leaves a triple 279 in col 8
strong link (8) in r4c89 means r8c8<>9 which leaves a naked pair 38
... but one of the xy-wings is still needed
edit (by popular request): last sentence changed from "but the xy-wings are still needed"
Last edited by nataraj on Fri Aug 29, 2008 6:05 pm; edited 1 time in total |
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sdq_pete
Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL
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| Posted: Fri Aug 29, 2008 11:03 am Post subject: |
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A single XYZ in Block 7 finishes it off...
Peter |
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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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| Posted: Fri Aug 29, 2008 12:44 pm Post subject: |
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All it took for me was a single XY wing. The puzzle falls apart after that
| Code: |
.---------------.---------------.---------------.
| 6 29 5 | 3 29 1 | 8 4 7 |
| 49 34 8 | 7 6 5 | 39 1 2 |
| 129 7 123 | 4 29 8 | 39 6 5 |
:---------------+---------------+---------------:
| 3 6 4 | 1 7 29 | 5 289 89 |
| 5 29 27 | 8 3 6 | 1 279 4 |
| 129 8 127 | 5 4 29 | 6 279 3 |
:---------------+---------------+---------------:
| 7 1 *23 | 9 8 34 | *24 5 6 |
| 48 5 6 | 2 1 34 | 7 389 89 |
| 248 *34 9 | 6 5 7 | 2-4 38 1 |
'---------------'---------------'---------------'
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Aug 29, 2008 2:09 pm Post subject: |
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I finished the basics too soon because I could not find any solution. Eventually the xy wing did it.
Last edited by cgordon on Fri Aug 29, 2008 6:07 pm; edited 1 time in total |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Aug 29, 2008 2:12 pm Post subject: |
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The xy-wing on <234> was also my solution.
Ted  |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Aug 29, 2008 4:37 pm Post subject: |
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| Quote: | | ... but the xy-wings are still needed |
Better make that singular my friend. 
I used the 34-38-48 pivoted in r9c2. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Fri Aug 29, 2008 6:07 pm Post subject: |
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| nataraj, at your service! |
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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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| Posted: Fri Aug 29, 2008 9:07 pm Post subject: Daily Sudoku:Fri 29-Aug-2008 VH |
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| XY-Wing 234 with Pivot {3,4}r9c2 eliminating 2 in r7c7 solves the puzzle. |
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sudocraz
Joined: 28 Apr 2008
Posts: 53
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| Posted: Sat Aug 30, 2008 12:48 am Post subject: |
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Please forgive me for this question, but how do you determine the pivot of an xy wing? 
I am still trying to learn these
Regards |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sat Aug 30, 2008 2:20 am Post subject: |
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| sudocraz wrote: | Please forgive me for this question, but how do you determine the pivot of an xy wing?
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Hello Sheila,
There are three bivalue cells in an XY-Wing! Here is the original PM marked for the first of three XY-Wings present. A is the pivotal cell because it contains a candidate in common with each of the two outlying a cells. Since the outlying a cells contain a common unlinked value (4), this value can be eliminated in any cell seeing both a cells. In the first XY-Wing, [r9c7]<>4 is the result.
| Code: | |-------------|
[r7c3]=23 & [r7c7]=24
[r7c3]=23 & [r9c2]=34
|------------|
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| Code: | +-----------------------------------------------------+
| 6 29 5 | 3 29 1 | 8 4 7 |
| 49 34 8 | 7 6 5 | 39 1 2 |
| 129 7 123 | 4 29 8 | 39 6 5 |
|-----------------+-----------------+-----------------|
| 3 6 4 | 1 7 29 | 5 289 89 |
| 5 29 27 | 8 3 6 | 1 279 4 |
| 129 8 127 | 5 4 29 | 6 279 3 |
|-----------------+-----------------+-----------------|
| 7 1 A23 | 9 8 34 | a24 5 6 |
| 48 5 6 | 2 1 34 | 7 389 89 |
| 248 a34 9 | 6 5 7 | 2-4 38 1 |
+-----------------------------------------------------+
# 39 eliminations remain
A a a
XY-Wing [r7c3]/[r7c7]+[r9c2] <> 4 [r9c7]
XY-Wing [r9c2]/[r7c3]+[r9c7] <> 2 [r7c7],[r9c1]
XY-Wing [r9c2]/[r8c1]+[r9c8] <> 8 [r8c89],[r9c1]
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Regards, Danny |
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kragzy
Joined: 01 May 2007
Posts: 112
Location: Australia
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| Posted: Sat Aug 30, 2008 12:49 pm Post subject: |
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Sheila,
In simple terms, the pivot in an XY wing is the pair that can see both of the other pairs.
You start with two pairs that have one comon digit, i.e. xy and xz, or xy and yz. Then you look for the third pair (yz, or xz respectively) in any row, column or box that can be seen by the two pairs. If you find the third pair then you have an XY wing. The pivot is the one that can see the other two.
Clear as mud?
Cheers |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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sudocraz
Joined: 28 Apr 2008
Posts: 53
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| Posted: Tue Sep 02, 2008 12:48 am Post subject: |
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Thanks to all of you, Danny, Krazygy,Marty. I am still stumbling around, but determined to learn xy wings. It is a lot easier if it forms a rectangle, but it doesn't often do that.
Will study what you have given me.
Thanks |
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