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Clement
Joined: 24 Apr 2006
Posts: 1110
Location: Dar es Salaam Tanzania
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 Posted: Fri Sep 11, 2015 11:41 pm Post subject: Sep 12 VH |
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| 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 |
+------------+-------------+----------+
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XY-Wing 89-2 pivoted in r8c3; r7c8<>2; stte |
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dongrave
Joined: 06 Mar 2014
Posts: 564
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| Posted: Sat Sep 12, 2015 3:06 pm Post subject: |
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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
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| Posted: Sat Sep 12, 2015 4:33 pm Post subject: |
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| 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
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: 564
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| Posted: Sat Sep 12, 2015 5:48 pm Post subject: |
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| 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
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| Posted: Sat Sep 12, 2015 6:50 pm Post subject: |
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| 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: 564
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| Posted: Sat Sep 12, 2015 7:50 pm Post subject: |
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| 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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