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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sat Feb 14, 2009 7:20 am Post subject: daily telegraph 2/13/09 |
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| Code: |
+-------+-------+-------+
| . 3 . | 1 8 6 | . 2 . |
| . . 8 | . . 3 | 1 . . |
| . . . | . . . | . . 4 |
+-------+-------+-------+
| . . . | 6 . . | 4 . . |
| 9 1 . | . . . | . 8 7 |
| . . 7 | . . . | . . . |
+-------+-------+-------+
| 7 . . | . . . | . . . |
| . . 1 | 3 . . | 5 . . |
| . 4 . | 5 2 7 | . 9 . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
| Quote: | not sure how to classify this one.
if you use the x-wing first, it rips through it pretty good.
a productive x-wing?? I thought they only existed in this site's VH puzzles. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Feb 14, 2009 4:59 pm Post subject: Re: daily telegraph 2/13/09 |
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| storm_norm wrote: |
a productive x-wing?? I thought they only existed in this site's VH puzzles. |
The (London) "Times" so-called "super fiendish" can usually be solved with x-wings (and the occasional swordfish thrown in). |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Feb 15, 2009 1:12 am Post subject: |
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I got stuck after an XYZ-Wing, Hidden UR and an X-Wing. Medusa will solve it easily but I can't help but think there's an XY-Chain, W-Wing or something similar that I'm missing.
| Code: |
+------------+-------------+-------------+
| 45 3 49 | 1 8 6 | 7 2 59 |
| 25 7 8 | 249 49 3 | 1 56 569 |
| 1 6 29 | 7 59 25 | 8 3 4 |
+------------+-------------+-------------+
| 3 8 25 | 6 7 9 | 4 1 25 |
| 9 1 46 | 24 345 25 | 236 8 7 |
| 46 25 7 | 248 134 148 | 9 56 2356 |
+------------+-------------+-------------+
| 7 259 235 | 89 169 18 | 23 4 2368 |
| 26 29 1 | 3 469 48 | 5 7 268 |
| 8 4 36 | 5 2 7 | 36 9 1 |
+------------+-------------+-------------+
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Play this puzzle online at the Daily Sudoku site |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Feb 15, 2009 6:57 am Post subject: |
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| Marty R. wrote: | I got stuck after an XYZ-Wing, Hidden UR and an X-Wing. Medusa will solve it easily but I can't help but think there's an XY-Chain, W-Wing or something similar that I'm missing.
| Code: |
+------------+-------------+-------------+
| 45 3 49 | 1 8 6 | 7 2 59 |
| 25 7 8 | 249 49 3 | 1 56 569 |
| 1 6 29 | 7 59 25 | 8 3 4 |
+------------+-------------+-------------+
| 3 8 25 | 6 7 9 | 4 1 25 |
| 9 1 46 | 24 345 25 | 236 8 7 |
| 46 25 7 | 248 134 148 | 9 56 2356 |
+------------+-------------+-------------+
| 7 259 235 | 89 169 18 | 23 4 2368 |
| 26 29 1 | 3 469 48 | 5 7 268 |
| 8 4 36 | 5 2 7 | 36 9 1 |
+------------+-------------+-------------+
|
Play this puzzle online at the Daily Sudoku site |
Marty,
there is an extended W-wing on {4,9} in the grid but doesn't get too far.
there are many xy-chains available and i know of one that will kill it.
there is also a pattern in the grid which is discussed in other forums called a "strong-wing" but its not easy to find since it involves three different candidates.
you can read more about it here
http://www.sudoku.com/boards/viewtopic.php?t=6553
in your grid you posted, the strong-wing can be found in r67c59
on candidates 3,6,1
and the strong-wing tells us that the 3 in r6c5 can be eliminated ( and solves the puzzle ).
WHY? 
| Code: |
+------------+-------------+-------------+
| 45 3 49 | 1 8 6 | 7 2 59 |
| 25 7 8 | 249 49 3 | 1 56 569 |
| 1 6 29 | 7 59 25 | 8 3 4 |
+------------+-------------+-------------+
| 3 8 25 | 6 7 9 | 4 1 25 |
| 9 1 46 | 24 345 25 | 236 8 7 |
| 46 25 7 | 248#134 148 | 9 56 2356#|
+------------+-------------+-------------+
| 7 259 235 | 89 #169 18 | 23 4 2368#|
| 26 29 1 | 3 469 48 | 5 7 268 |
| 8 4 36 | 5 2 7 | 36 9 1 |
+------------+-------------+-------------+
|
as you notice the cells form a rectangle, also notice that on three sides of the rectangle one of the candidates is conjugate.
3's are conjugate in col 9,
6's are conjugate in row 7
1's are conjugate in col 5
these conjugate candidates form the 3 sides of the rectangle.
so in our example
we started with the 3 in r6c9..... then down to the 3 in r7c9
6 in r7c9 over to 6 in r7c5
1 in r7c5 up to 1 in r6c5
to form the rectangle.
the elimination occurs if there is a 3 in that last cell with the 1.
in this case there is and can be eliminated.
more generally this is how the pattern would look.
| Code: | -AC................A
. .
C's conjugate . . A's conjugate
. .
. .
BC................AB
B's conjugate |
obviously the pattern does not have to be a rectangle, and would probably not be readily seen in other patterns. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sun Feb 15, 2009 9:05 am Post subject: |
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| Norm: There's a conjugate link for <3> on the fourth side of your rectangle. Although you don't need to use it, it adds a whole new perspective on those four cells. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Feb 15, 2009 9:12 am Post subject: |
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| daj95376 wrote: | | Norm: There's a conjugate link for <3> on the fourth side of your rectangle. That should add a new dimension to your eliminations. |
Danny,
HA!
I knew you would point that out.
I wasn't going to mention that because the general rule of the strong-wing doesn't need that 4th conjugate link.
but as it stands, this is your discontinuous loop that you have pointed out in the past. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Feb 15, 2009 4:40 pm Post subject: |
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| Thank you!! |
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