| View previous topic :: View next topic |
| Author |
Message |
cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
|
 Posted: Thu Jul 05, 2007 6:27 pm Post subject: |
 |
|
| Apologies if I've missed something here. But it seems that here we have traced a link from one 19 to another 19 such that IF the first cell is a 1 then the other has to be a 9 - and vice-versa. But surely a good technique should tell us which is the 1 and which is the 9 - right off the bat. Otherwise why not just go to the first 19 and say "let x = 1"and see where it goes. An assumption is an assumption. Again, apologies if I've missed the point. |
|
| Back to top |
|
 |
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Thu Jul 05, 2007 6:44 pm Post subject: |
|
|
The point is:
Either R3C6 and / or R7C2 is <9>. Thus R3C2 cannot be <9>. Which causes a pair <16> in R3, which solves the puzzle because R3C6 is <9>, etc.
Keith |
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Thu Jul 05, 2007 7:31 pm Post subject: Ponder This |
|
|
I notice that a W-Wing could serve as a "Bridge" for a color wrap. The idea is of no use in the two examples in this thread, and I don't even know if such an occurrence exists. But, it would be neat if someone found one.
To clarify, borrowing Keith's schematic for the W-Wing:
<XY> -- <X-Strong Link-X> -- <XY>
For purposes of the W-Wing, we focus on the fact that one or both of the bivalue cells must be <Y>.
But, the converse statement that the bivalue cells cannot both be <X> qualifies them to serve as a Bridge for a Color Wrap on <X>.
I'll be on the lookout for one. |
|
| Back to top |
|
|
cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
|
| Posted: Thu Jul 05, 2007 7:39 pm Post subject: |
|
|
| Thanks - but I'll stick to the simple xy wing that was originally needed to solve this one. The above "W wing variations" seem like using a sledge-hammer to crack a walnut. Definitely wouldn't agree they are easier than xy wings or skyscrapers. |
|
| Back to top |
|
|
ravel
Joined: 21 Apr 2006
Posts: 536
|
| Posted: Thu Jul 05, 2007 7:49 pm Post subject: |
|
|
| keith wrote: | jLo said: | Quote: | | In the July 2 puzzle there is a W-Wing with the pair "19" |
So far as I can see, correct, but not so simple. |
Hm. did you miss the strong link for 1 in column 1 ?
| Code: | +--------------+-------------+-------------+
| 7 128 3 | 15 6 4 | 28 9 258 |
| 29 28 94 | 359 7 359 | 6 1 258 |
|#16 169$ 5 | 2 8 19@ | 4 3 7 |
+-------------+-------------+-------------+
| 4 7 9 | 6 5 23 | 1 28 238 |
| 38 5 28 | 13 4 12 | 9 7 6 |
| 36 26 1 | 7 9 8 | 23 5 4 |
+--------------+-------------+-------------+
| 5 19@ 28 | 4 3 6 | 7 28 19 |
|#18 4 7 | 59 2 59 | 38 6 138 |
| 29 3 6 | 8 1 7 | 5 4 29 |
+--------------+-------------+-------------+ |
|
|
| Back to top |
|
|
Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
|
| Posted: Thu Jul 05, 2007 8:34 pm Post subject: |
|
|
Ravel,
I think the point was that there are many different ways to find the needed strong link. (There is also one in Row 1.)
From the "Y-Wing" link in your Other Puzzles post today, it is clear that the W-Wing is one example of gsf's more general category of "Y-Wing" (as are X-Wings, XY-Wings and almost all the commonly named techniques!). However, the "Y-Wing" discussion goes right over the head of most of us casual sudoku types... or at least this one! Still, gsf clearly described the "W-Wing" back in March and recommended it as an easy to spot method. |
|
| Back to top |
|
|
ravel
Joined: 21 Apr 2006
Posts: 536
|
| Posted: Fri Jul 06, 2007 7:52 am Post subject: |
|
|
| Asellus wrote: | | I think the point was that there are many different ways to find the needed strong link. |
I see, sorry, i did not read all of the thread. | Quote: | | From the "Y-Wing" link in your Other Puzzles post today, it is clear that the W-Wing is one example of gsf's more general category of "Y-Wing" (as are X-Wings, XY-Wings and almost all the commonly named techniques!). However, the "Y-Wing" discussion goes right over the head of most of us casual sudoku types... or at least this one! Still, gsf clearly described the "W-Wing" back in March and recommended it as an easy to spot method. |
As i see it, Steve K first described it as an example of his "Y Wing styles", but i am not sure (when you search for "Y Wing", you get all threads with wings).
I only think to remember, that rep'nA used W-Wings calling them Y Wings (probably because there was no own name for this type of "Y Wing style"). Btw all his posts mysteriously vanished and he is now posting as "re'born" 
I also think, that it is rarely known, that W-Wings are rather common in puzzles and (as Marty demonstrated again) often easier to spot that xy-wings. So it is worth to be looked at as an own technique. |
|
| Back to top |
|
|
keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
|
| Posted: Fri Jul 06, 2007 8:31 am Post subject: |
|
|
| ravel wrote: | | keith wrote: | jLo said: | Quote: | | In the July 2 puzzle there is a W-Wing with the pair "19" |
So far as I can see, correct, but not so simple. |
Hm. did you miss the strong link for 1 in column 1 ?
|
Yes I did! And the one pointed out be Asellus!
I was looking for links which line up in a row or column, and neglected to look at those in the same box. A franken W-wing, I suppose.
Best wishes,
Keith |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
