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Clement
Joined: 24 Apr 2006
Posts: 1110
Location: Dar es Salaam Tanzania
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 Posted: Thu Oct 07, 2010 11:25 pm Post subject: Oct 8 VH |
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Three steps
1) X-wing 1 in Grid r19c68 eliminates 1 in r1c49 and r9c35 followed by
2) Finned X-Wing 9 in Grid r58c25 removes 9 in r4c5 and
3) XY-Wing 59 25 29 Pivoted in r4c5 eliminating 9 in r9c3 which solves the puzzle. |
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kuskey
Joined: 10 Dec 2008
Posts: 141
Location: Pembroke, NH
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| Posted: Fri Oct 08, 2010 4:14 am Post subject: 8 Oct VH |
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| A 159 xy-wing with pivot at r5c5 eliminating 9 at r8c2 does it in one step. |
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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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| Posted: Fri Oct 08, 2010 10:16 am Post subject: |
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| All I needed was a 15-59-19 XY-Wing. |
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Ema Nymton
Joined: 17 Apr 2009
Posts: 89
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| Posted: Sun Oct 10, 2010 9:33 am Post subject: Re: Oct 8 VH |
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Please forgive me for being dense, perhaps this is one of those 'teaching moments.'
| Clement wrote: | Three steps
1) X-wing 1 in Grid r19c68 eliminates 1 in r1c49 and r9c35 followed by
2) Finned X-Wing 9 in Grid r58c25 removes 9 in r4c5 and
3) XY-Wing 59 25 29 Pivoted in r4c5 eliminating 9 in r9c3 which solves the puzzle. |
| Code: |
+----------+------------+----------+
| 9 27 6 | 5 1278 12 | 3 14 148 |
| 5 27 4 | 12 1278 3 | 9 6 18 |
| 1 8 3 | 4 6 9 | 2 5 7 |
+----------+------------+----------+
| 4 6 59 | 29 259* 7 | 1 8 3 |
| 3 59A 8 | 19 159B 4 | 6 7 2 |
| 2 1 7 | 6 3 8 | 4 9 5 |
+----------+------------+----------+
| 6 3 1 | 7 4 5 | 8 2 9 |
| 7 49 2 | 8 19C 6 | 5 3 14 |
| 8 459 59 | 3 129 12 | 7 14 6 |
+----------+------------+----------+
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"Finned X-Wing 9 in Grid r58c25 removes 9 in r4c5"
Why is there a relationship amoung the cells ABC that remove the '9' from r4c5? Would not the relationship also remove the '9' from r9c5 and '9' from r5c4?
Ema Nymton
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Sun Oct 10, 2010 11:38 am Post subject: |
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Ema
There are two things going on in a "finned x-wing".
(1) There is "nearly" an x-wing in r5c2 & r5c5 and r8c2 & r8c5
... if it weren't for ...
(2) The "fin" 9 in r5c4 (which stops the x-wing existing)
The logic goes like this..
If the fin is not a 9, then the x-wing exists and the possible eliminations are r9c2<>9, r4c5<>9, r9c5<>9
If the fin is a 9 then anything seen by that 9 could be eliminated
Only one of these two situations can exist (we don't know which). However, because one must exist any elimination that is common to both paths can be made. In this case, r4c5<>9.
In shorthand, a finned x-wing makes only those eliminations that the x-wing makes in the same box as the fin.
Peter |
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