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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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 Posted: Thu Feb 18, 2010 12:14 am Post subject: Feb 18 VH |
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1. XY-Wing <35>-<57>-<37> eliminating 3 in r7c5 leads to
2. XYZ-Wing <36>-<367>-<37> eliminating 3 in r1c9 solving the puzzle. |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Thu Feb 18, 2010 2:53 am Post subject: Feb 18 |
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xy-chain (36-37-37-36) eliminates the 6 in R9C3 and solves the puzzle.
Earl |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Feb 18, 2010 6:00 am Post subject: |
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| After the 375 XY-Wing there was a BUG+2 in row 1. The two possibilities were 36, which combined with a 36 cell to form a naked pair which finished it off. |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Thu Feb 18, 2010 7:42 am Post subject: |
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| w-wing 63 removing a 6 in r9c3 will do it in one step. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Thu Feb 18, 2010 3:02 pm Post subject: |
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I used a Type 6 UR (13) to remove <1> from R9C3 and R8C9. Then an ER on <3>.
Which was pretty cool really. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Feb 19, 2010 1:55 pm Post subject: |
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| cgordon wrote: | I used a Type 6 UR (13) to remove <1> from R9C3 and R8C9. Then an ER on <3>.
Which was pretty cool really. |
I also find UR implication very useful. They also seemed to be very productive in providing one step solutions.
In this puzzle, it is the x-wing 1 overlay on the UR13 that allows the removal of digit 1 in r8c9 and r9c3. But if the x-wing 1 was not present, the UR still offers deletions because of the strong inference between the 7 in r8c9 and the 6 in r9c3. One of these two must be true to prevent the deadly pattern: (7)r8c9 = (6)r9c3.
One possible chain using this inference is:
(3=7)r7c2 - (7=3)r2c2 - (3=6)r1c3 - UR13[(6)r9c3 = (7)r8c9]r89c39 - (7=5)r8c1 - (5=3)r8c5; r7c5<>3.
In this specific case, I suspect the end results of both approaches are identical.
Ted |
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