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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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 Posted: Fri Oct 24, 2008 2:01 am Post subject: Oct 24 VH |
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6-7-8 xy-wing is sufficient. Apparent coloring (7) is not necessary.
Earl |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Fri Oct 24, 2008 2:44 am Post subject: Re: Oct 24 VH |
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| Earl wrote: | 6-7-8 xy-wing is sufficient. Apparent coloring (7) is not necessary.
Earl |
Anybody solve this without advanced techniques/wings?
| Code: |
+--------------+-----------+----------+
| 9 468 467 | 3 1 67 | 68 2 5 |
| 67 5 3 | 8 9 2 | 46 1 47 |
| 1 68 2 | 4 5 67 | 3 78 9 |
+--------------+-----------+----------+
| 3 7 9 | 6 8 5 | 2 4 1 |
| 4 2 8 | 1 7 3 | 9 5 6 |
| 56 1 56 | 9 2 4 | 7 3 8 |
+--------------+-----------+----------+
| 28 46 1 | 27 46 9 | 5 78 3 |
| 28 9 457 | 257 3 1 | 48 6 47 |
| 567 3 4567 | 57 46 8 | 1 9 2 |
+--------------+-----------+----------+
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Play this puzzle online at the Daily Sudoku site |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Oct 24, 2008 4:07 am Post subject: |
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Another one-stepper is a w-wing <67> located at r1c6 & r2c1 with strong link <6> in col7. Deletion of <7> from r1c3 finishes off the puzzle.
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Fri Oct 24, 2008 4:40 am Post subject: Re: Oct 24 VH |
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| crunched wrote: | Anybody solve this without advanced techniques/wings?
| Code: | +--------------+-----------+----------+
| 9 468 467 | 3 1 67 | 68 2 5 |
| 67 5 3 | 8 9 2 | 46 1 47 |
| 1 68 2 | 4 5 67 | 3 78 9 |
+--------------+-----------+----------+
| 3 7 9 | 6 8 5 | 2 4 1 |
| 4 2 8 | 1 7 3 | 9 5 6 |
| 56 1 56 | 9 2 4 | 7 3 8 |
+--------------+-----------+----------+
| 28 46 1 | 27 46 9 | 5 78 3 |
| 28 9 457 | 257 3 1 | 48 6 47 |
| 567 3 4567 | 57 46 8 | 1 9 2 |
+--------------+-----------+----------+
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From your PM:
Locked Candidate 1 => [r8c3]<>4
Skyscraper => [r8c3]<>7
Singles
BUG+1 => [r1c2]=6 |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Fri Oct 24, 2008 1:54 pm Post subject: |
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| tlanglet wrote: | Another one-stepper is a w-wing <67> located at r1c6 & r2c1 with strong link <6> in col7. Deletion of <7> from r1c3 finishes off the puzzle.
Ted |
My solver tool box uses the x, xy, xyz wings. That is essentially it.
I am trying to expand that. Why wouldn't the w-wing, pointed out here, eliminate both <6> & <7> in r1c3? If not both, why does it eliminate <7> rather than <6> ? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Oct 24, 2008 3:50 pm Post subject: |
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| Quote: | | Why wouldn't the w-wing, pointed out here, eliminate both <6> & <7> in r1c3? If not both, why does it eliminate <7> rather than <6> ? |
Have you read the W-Wing explanation here?
http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2143
Someone could probably give a better answer than I can, but with the strong link on 6 in column 7, that forces one or the other of the 67 pairs to be = 7, thus the 7s act as pincers. |
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Clement
Joined: 24 Apr 2006
Posts: 1113
Location: Dar es Salaam Tanzania
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| Posted: Fri Oct 24, 2008 5:07 pm Post subject: Daily Sudoku: Fri 24-Oct-2008 VH |
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| XY-Wing Pivot {6,8}r3c2 with Pincers in r2c1{6,7} and r3c8{7,8} eliminating 7 in r2c9 solves the puzzle. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Fri Oct 24, 2008 6:00 pm Post subject: |
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| Marty R. wrote: | | Quote: | Why wouldn't the w-wing, pointed out here, eliminate both <6> & <7> in r1c3?
If not both, why does it eliminate <7> rather than <6> ? |
... with the strong link on 6 in column 7, that forces one or the other of the 67 pairs to be = 7, thus the 7s act as pincers. |
At the risk of repeating Marty's reply, there's an alternate way of viewing this 4-cell W-Wing. Work from the inside out!
Consider the strong link on 6 in [c7]. Either [r1c7]=6 or else [r2c7]=6.
| Code: | [r1c7]=6 => [r1c6]=7 => [r1c3]<>7
[r2c7]=6 => [r2c1]=7 => [r1c3]<>7
+--------------------------------------------------------------+
| 9 468 46-7 | 3 1 #67 | *68 2 5 |
| #67 5 3 | 8 9 2 | *46 1 47 |
| 1 68 2 | 4 5 67 | 3 78 9 |
|--------------------+--------------------+--------------------|
| 3 7 9 | 6 8 5 | 2 4 1 |
| 4 2 8 | 1 7 3 | 9 5 6 |
| 56 1 56 | 9 2 4 | 7 3 8 |
|--------------------+--------------------+--------------------|
| 28 46 1 | 27 46 9 | 5 78 3 |
| 28 9 457 | 257 3 1 | 48 6 47 |
| 567 3 4567 | 57 46 8 | 1 9 2 |
+--------------------------------------------------------------+
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Although setting [r1c7]=6 will also produce the eliminations [r1c23]<>6, setting [r2c7]=6 does not produce either of these eliminations.
Now, to confuse you even further, there's also a strong link on 6 in [r3].
Wanna bet there's another 4-cell W-Wing for the same elimination? |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Oct 24, 2008 10:21 pm Post subject: |
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| There's an ER on 7 that gets rid of the 7 in R8C3. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat Oct 25, 2008 4:09 am Post subject: |
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| Marty R. wrote: | | Quote: | | Why wouldn't the w-wing, pointed out here, eliminate both <6> & <7> in r1c3? If not both, why does it eliminate <7> rather than <6> ? |
Have you read the W-Wing explanation here?
http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2143
Someone could probably give a better answer than I can, but with the strong link on 6 in column 7, that forces one or the other of the 67 pairs to be = 7, thus the 7s act as pincers. |
This strong link on 6 is considered a strong link because there are only 2 sixes in that column?
Yes, I have read the tutorial, and I need to keep referring back to it. This stuff does not immediately sink in. At some point I will get the "aha" moment and it will become easy to apply---I think!
It is a nice tutorial, thanks. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat Oct 25, 2008 4:11 am Post subject: |
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This was good. I like the way you explained the logic involved in this.
Thanks.
| daj95376 wrote: | | Marty R. wrote: | | Quote: | Why wouldn't the w-wing, pointed out here, eliminate both <6> & <7> in r1c3?
If not both, why does it eliminate <7> rather than <6> ? |
... with the strong link on 6 in column 7, that forces one or the other of the 67 pairs to be = 7, thus the 7s act as pincers. |
At the risk of repeating Marty's reply, there's an alternate way of viewing this 4-cell W-Wing. Work from the inside out!
Consider the strong link on 6 in [c7]. Either [r1c7]=6 or else [r2c7]=6.
| Code: | [r1c7]=6 => [r1c6]=7 => [r1c3]<7> [r2c1]=7 => [r1c3]<>7
+--------------------------------------------------------------+
| 9 468 46-7 | 3 1 #67 | *68 2 5 |
| #67 5 3 | 8 9 2 | *46 1 47 |
| 1 68 2 | 4 5 67 | 3 78 9 |
|--------------------+--------------------+--------------------|
| 3 7 9 | 6 8 5 | 2 4 1 |
| 4 2 8 | 1 7 3 | 9 5 6 |
| 56 1 56 | 9 2 4 | 7 3 8 |
|--------------------+--------------------+--------------------|
| 28 46 1 | 27 46 9 | 5 78 3 |
| 28 9 457 | 257 3 1 | 48 6 47 |
| 567 3 4567 | 57 46 8 | 1 9 2 |
+--------------------------------------------------------------+
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Although setting [r1c7]=6 will also produce the eliminations [r1c23]<>6, setting [r2c7]=6 does not produce either of these eliminations.
Now, to confuse you even further, there's also a strong link on 6 in [r3].
Wanna bet there's another 4-cell W-Wing for the same elimination? |
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DennyOR
Joined: 12 Sep 2007
Posts: 33
Location: Portland, Oregon
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| Posted: Sat Oct 25, 2008 7:58 pm Post subject: |
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| And the 68-87-74-46 chain also solves the puzzle. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Oct 25, 2008 9:05 pm Post subject: |
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| crunched wrote: | This strong link on 6 is considered a strong link because there are only 2 sixes in that column?
Yes, I have read the tutorial, and I need to keep referring back to it. This stuff does not immediately sink in. At some point I will get the "aha" moment and it will become easy to apply---I think!
It is a nice tutorial, thanks. |
This will get you to "Aha" much quicker:
http://www.sudoku.com/boards/viewtopic.php?t=3326
Best wishes,
Keith |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sun Oct 26, 2008 11:34 pm Post subject: |
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Wow, that was a good tutorial on strong lengths and buddies. I think I will be able to put this to use, especially with skyscrapers---and 2-string kites too.  . Thanks for the heads-up on that!
| keith wrote: | | crunched wrote: | This strong link on 6 is considered a strong link because there are only 2 sixes in that column?
Yes, I have read the tutorial, and I need to keep referring back to it. This stuff does not immediately sink in. At some point I will get the "aha" moment and it will become easy to apply---I think!
It is a nice tutorial, thanks. |
This will get you to "Aha" much quicker:
http://www.sudoku.com/boards/viewtopic.php?t=3326
Best wishes,
Keith |
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