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Sep 12 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Fri Sep 11, 2015 11:41 pm    Post subject: Sep 12 VH Reply with quote

Code:

+------------+-------------+----------+
| 24  5   6  | 1    24  8  | 9  3  7  |
| 7   239 19 | 5    26  36 | 28 4  18 |
| 248 234 18 | 247  9   37 | 5  12 6  |
+------------+-------------+----------+
| 59  8   2  | 3    1   79 | 6  57 4  |
| 59  7   3  | 49   456 69 | 1  8  2  |
| 1   6   4  | 78   578 2  | 3  57 9  |
+------------+-------------+----------+
| 6   29  7  | 289  3   5  | 4  1-2 18 |
| 3   1   89 | 2789 278 4  | 28 6  5  |
| 248 24  5  | 6    28  1  | 7  9  3  |
+------------+-------------+----------+
XY-Wing 89-2 pivoted in r8c3; r7c8<>2; stte
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sat Sep 12, 2015 3:06 pm    Post subject: Reply with quote

I had the same solution as Clement but his grid has locked 9's in box 8 (or in column 6 of box 5) which gives you the following grid after basics.
Code:

 +------------+-------------+----------+
 | 2   5   6  | 1    4   8  | 9  3  7  |
 | 7   39  19 | 5    26  36 | 28 4  18 |
 | 48  34  18 | 27   9   37 | 5  12 6  |
 +------------+-------------+----------+
 | 59  8   2  | 3    1   79 | 6  57 4  |
 | 59  7   3  | 4    56  69 | 1  8  2  |
 | 1   6   4  | 78   578 2  | 3  57 9  |
 +------------+-------------+----------+
 | 6   29  7  | 289  3   5  | 4  12 18 |
 | 3   1   89 | 2789 278 4  | 28 6  5  |
 | 48  24  5  | 6    28  1  | 7  9  3  |
 +------------+-------------+----------+
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bat999



Joined: 09 Jul 2015
Posts: 55
Location: UK

PostPosted: Sat Sep 12, 2015 4:33 pm    Post subject: Reply with quote

dongrave wrote:
I had the same solution...
Hi Don
Do you see how that XY-wing can be expressed in Eureka notation as an AIC to make a pincer attack?
(The pincers are the twos in r8c7 and r7c2)

(2=8)r8c7 - (8=9)r8c3 - (9=2)r7c2 => -2 r7c8; stte

"If r8c7<>2 then r7c2=2"

In this chain some links may be compressed and the "passenger" candidate (8) omitted (2=8)r8c7 - (8=9)r8c3 --> (2=9)r8c37

Code:
.--------------.---------------.--------------.
| 2    5    6  | 1     4    8  |  9   3    7  |
| 7    39   19 | 5     26   36 |  28  4    18 |
| 48   34   18 | 27    9    37 |  5   12   6  |
:--------------+---------------+--------------:
| 59   8    2  | 3     1    79 |  6   57   4  |
| 59   7    3  | 4     56   69 |  1   8    2  |
| 1    6    4  | 78    578  2  |  3   57   9  |
:--------------+---------------+--------------:
| 6   b29   7  | 289   3    5  |  4   1-2  18 |
| 3    1   a89 | 2789  278  4  | a28  6    5  |
| 48   24   5  | 6     28   1  |  7   9    3  |
'--------------'---------------'--------------'
(2=9)r8c37 - (9=2)r7c2 => -2 r7c8; stte
Cool


Last edited by bat999 on Sat Sep 12, 2015 7:45 pm; edited 1 time in total
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sat Sep 12, 2015 5:48 pm    Post subject: Reply with quote

Thanks for explaining that Bat! I did take the time to write out a pedestrian Eureka expression (I used the same cells to show that if r7c8=2 then r7c2=9 so r8c3=8 so r8c7=2) but I didn't know about compressing the passenger like that! I'll remember that! And I also see now that even though the chain I wrote out uses the same cells, it's not an exact representation of the wing like yours is. Thanks again, Don.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sat Sep 12, 2015 6:50 pm    Post subject: Reply with quote

I'm having trouble following this conversation, not sure-of what both Bat and Don are trying to say.
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dongrave



Joined: 06 Mar 2014
Posts: 568

PostPosted: Sat Sep 12, 2015 7:50 pm    Post subject: Reply with quote

Marty R. wrote:
I'm having trouble following this conversation, not sure-of what both Bat and Don are trying to say.

Hi Marty! Because of a recent question that I had about Eureka, Bat was just pointing out to me how the 89-2 XY-Wing could be expressed in Eureka with the two pincers in r8c7 and r7c2. First, he listed an uncompressed Eureka expression (i.e. '(2=8)r8c7-(8=9)r8c3-(9=2)r7c2 = -2 r7c8; stte') and then he explained that the beginning of the expression (i.e. '(2=8)r8c7-(8=9)r8c3') could be shortened by eliminating what he called the 'passenger' (i.e. the '8') by replacing it with the sub-expression '(2=9)r8c37'. I didn't know that so I thanked him and listed the English version of a chain that I had written out (which I always do because I'm still working on my Eureka). The English 'If then' expression that I had used was (1=2)r7c8-(2=9)r7c2-(9=8)r8c3-(8=2)r8c7 => r7c8=1 which of course uses the exact same cells as the XY-Wing but I thought that Bat's Eureka expression was an exact representation of the XY-Wing whereas mine was not (because each end of his chain is a pincer that works exactly like the XY-Wing).
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