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hughwill
Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK
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 Posted: Fri Nov 27, 2015 12:33 pm Post subject: Nov 27 VH |
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After basics: | Code: |
+--------------+------------+----------+
| 13 7 4 | 5 13 6 | 2 8 9 |
| 238 289 5 | 78 37 789 | 1 6 4 |
| 6 89 18 | 4 2 189 | 3 5 7 |
+--------------+------------+----------+
| 5 14 9 | 2 8 134 | 6 7 13 |
| 12478 28 3 | 17 6 147 | 5 9 12 |
| 127 6 12 | 137 9 5 | 8 4 123 |
+--------------+------------+----------+
| 14 14 6 | 9 5 2 | 7 3 8 |
| 28 5 7 | 138 4 138 | 9 12 6 |
| 9 3 28 | 6 17 178 | 4 12 5 |
+--------------+------------+----------+
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Play this puzzle online at the Daily Sudoku site
I managed this in 3: | Quote: | 128 XY-Wing in boxes 1 and 4
followed by 781 XY-wing and 781 XYZ-wing |
But I'm sure that there's a quicker way somewhere....
(Edit- Oh yes, I see. The X -wing on 8 in C14 replaces the two 781 wings...)
Hugh |
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the_lock_man
Joined: 18 Dec 2012
Posts: 40
Location: Portsmarfff, UK
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| Posted: Fri Nov 27, 2015 12:58 pm Post subject: Is it an X Wing? |
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I must admit to having a mental block about X Wings, but surely the possible 8 in R5C1 stops there being an X Wing on 8 in columns 1 & 4?
Apologies if I'm being a bit of a thicko. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Nov 27, 2015 4:14 pm Post subject: |
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| Lock man beat me to the punch. I was just about to write the same thing. |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Fri Nov 27, 2015 4:44 pm Post subject: |
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It's easy to miss it - there are so many candidates in that cell that it practically runs into the next one! I think I saw an 8 X-Wing after the 1st XY-Wing (in two different columns) but I don't think it did much. Using only standard VH moves, I had to use the 3 wings that Hugh originally posted. Lately I'm on a one-step chain-finding kick too. Here's what I found (let me know if I screwed up again Marty). (3=1)r1c1-(1=8)r3c3-(8=2)r9c3-(2=8)r8c1-(8=13)r8c46-(1=7)r9c5-(7=3)r2c5=>r1c5=1; which solves it.
(Edit) I see now that I didn't need to use the 13 pair: (3=1)r1c1-(1=8)r3c3-(8=2)r9c3-(2=1)r9c8-(1=7)r9c5-(7=3)r2c5=>r1c5=1. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Nov 27, 2015 6:34 pm Post subject: |
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| Don, they're both fine. The only comment I want to make is about the conclusion =>r1c5=1. It's customary to show the conclusion as an elimination except under certain circumstances. In this case it would be => -3r1c5. After all, that's what pincers do, deny the existence of the pincer value. |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Fri Nov 27, 2015 7:06 pm Post subject: |
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| Marty R. wrote: | | Don, they're both fine. The only comment I want to make is about the conclusion =>r1c5=1. It's customary to show the conclusion as an elimination except under certain circumstances. In this case it would be => -3r1c5. After all, that's what pincers do, deny the existence of the pincer value. |
Oh! Of course. I see! Thanks Marty! |
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hughwill
Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK
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| Posted: Sat Nov 28, 2015 9:25 am Post subject: Re: Is it an X Wing? |
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| the_lock_man wrote: | I must admit to having a mental block about X Wings, but surely the possible 8 in R5C1 stops there being an X Wing on 8 in columns 1 & 4?
Apologies if I'm being a bit of a thicko. |
The X-wing on 8 appears after the 128 XY-Wing which sets r5c2 to 8 thus
removing the 8 in r5c1. Sorry, I should have made it clearer.
Hugh |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Sat Nov 28, 2015 5:44 pm Post subject: |
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| I'm confused Hugh. I remembered seeing an 8 X-Wing yesterday after the 1st XY-Wing so I went back and looked today. I missed yours in C14 but I saw the one in R39 and they both appear to remove the same candidate (i.e. the 8 from r8c6). I'm pretty sure yesterday that I still had to perform the next XY-Wing (78-1 with pivot at r2c4) followed by a 13-8 XY-Wing (instead of the XYZ-Wing) with pivot at r8c6 so the X-Wing didn't do much for me (other than change the XYZ-Wing to an XY-Wing). Am I missing something? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Nov 28, 2015 9:51 pm Post subject: |
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After basics,
| Code: | +-------------------+-------------------+-------------------+
| 13 7 4 | 5 13 6 | 2 8 9 |
| 238 289 5 | 78 37 789 | 1 6 4 |
| 6 89 18 | 4 2 189 | 3 5 7 |
+-------------------+-------------------+-------------------+
| 5 14 9 | 2 8 134 | 6 7 13 |
| 12478 28 3 | 17 6 147 | 5 9 12 |
| 127 6 12 | 137 9 5 | 8 4 123 |
+-------------------+-------------------+-------------------+
| 14 14 6 | 9 5 2 | 7 3 8 |
| 28 5 7 | 138 4 138 | 9 12 6 |
| 9 3 28 | 6 17 178 | 4 12 5 |
+-------------------+-------------------+-------------------+ |
There is an XY-wing 12-8 in C23.
Then, there is an X-wing (8) in R39. Yes, there is an XYZ-wing that makes the same elimination in R8C6. Or, there is an XY-wing -178 that takes out 1 in R45C6.
Keith |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Sat Nov 28, 2015 10:37 pm Post subject: |
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I'm still confused. Maybe I'm missing something. From Hugh's or Keith's grid I see a 12-8 XY-Wing with pivot at r6c3 that removes the 8 from r23c2. Then I perform basics until I get to the following grid:
| Code: |
+--------------+------------+----------+
| 13 7 4 | 5 13 6 | 2 8 9 |
| 38 2 5 | 78 37 9 | 1 6 4 |
| 6 9 18 | 4 2 18 | 3 5 7 |
+--------------+------------+----------+
| 5 14 9 | 2 8 134 | 6 7 13 |
| 1247 8 3 | 17 6 147 | 5 9 12 |
| 127 6 12 | 137 9 5 | 8 4 123 |
+--------------+------------+----------+
| 14 14 6 | 9 5 2 | 7 3 8 |
| 28 5 7 | 138 4 138 | 9 12 6 |
| 9 3 28 | 6 17 178 | 4 12 5 |
+--------------+------------+----------+
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And at this point I see Hugh's 8 X-Wing in C14 which removes the 8 from r8c6 and I see Keith's 8 X-Wing in R39 which removes the same candidate but after that I don't see a solution unless I play the 78-1 XY-Wing with pivot at r2c4 eliminating the 1 from r45c6 followed by a 13-8 XY-Wing with pivot at r8c6 removing the 8 from r2c4. But if that's the case, then the X-Wing didn't do much at all for me because it cost me an extra advanced move to make the last Wing an XY-Wing instead of an XYZ-Wing. Am I missing something? |
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hughwill
Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK
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| Posted: Sun Nov 29, 2015 11:42 pm Post subject: |
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| dongrave wrote: | | Am I missing something? |
No, I don't think so.
Hugh  |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Mon Nov 30, 2015 12:07 am Post subject: |
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| hughwill wrote: | | dongrave wrote: | | Am I missing something? |
No, I don't think so.
Hugh |
You have nothing to be embarrassed about Hugh! I make more mistakes than I do correct moves. It was just driving me crazy that I didn't see it! Keep up the great work! |
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