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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Wed Jun 25, 2008 11:00 pm Post subject: I thought I was getting good, then ... |
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This one trips me up: | Code: | Puzzle: M6498989sh(21)
+-------+-------+-------+
| . . 6 | . . 1 | 8 . . |
| 8 . . | . 7 . | . . 6 |
| . . . | . 3 6 | . . . |
+-------+-------+-------+
| . 7 . | 6 . 3 | . 5 . |
| 3 . 5 | . . . | 6 . 7 |
| . 8 9 | 4 . 7 | 3 2 . |
+-------+-------+-------+
| . . . | . 4 5 | . . . |
| 2 . . | . 1 . | . . 9 |
| . . 4 | . . 2 | 5 . . |
+-------+-------+-------+ |
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Jun 26, 2008 5:15 am Post subject: |
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The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid. After that I'm thinking Medusa is all that's left in my arsenal.
Last edited by Marty R. on Thu Jun 26, 2008 3:46 pm; edited 1 time in total |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Thu Jun 26, 2008 6:34 am Post subject: |
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| Code: | .---------------------.---------------------.---------------------.
| 457 34 6 | 2 9 1 | 8 347 345 |
| 8 1239 123 | 5 7 4 | 12 139 6 |
| 14579 1249 127 | 8 3 6 | 127 1479 245 |
:---------------------+---------------------+---------------------:
| 14 7 12 | 6 28 3 | 9 5 48 |
| 3 24 5 | 1 28 9 | 6 48 7 |
| 6 8 9 | 4 5 7 | 3 2 1 |
:---------------------+---------------------+---------------------:
| 179 6 8 | 379 4 5 | 127 137 23 |
| 2 5 37 | 37 1 8 | 4 6 9 |
| 179 139 4 | 379 6 2 | 5 1378 38 |
'---------------------'---------------------'---------------------' |
one step solution
xy-chain(3=8)r9c9-(8=4)r4c9-(4=1)r4c1-(1=2)r4c3-(2=4)r5c2-(4=3)r2c2; r9c2 and r1c9 <> 3 |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Thu Jun 26, 2008 10:54 am Post subject: |
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Nice catch Norm !
These xy-chains maybe underestimated, but it solves this grid in one fell swoop. Nevertheless i like these chains, they can be a powerful tool to break the
puzzle wide open. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Jun 26, 2008 12:03 pm Post subject: |
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| Marty R. wrote: | | The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid. |
Marty, I looked at the two potential <12>URs last night and again this morning after seeing you comments, but I still fail to see an elimination. (and yes, I had my coffee this morning.)
What is invalid? 
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Jun 26, 2008 3:44 pm Post subject: |
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| tlanglet wrote: | | Marty R. wrote: | | The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid. |
Marty, I looked at the two potential <12>URs last night and again this morning after seeing you comments, but I still fail to see an elimination. (and yes, I had my coffee this morning.)
What is invalid?
Ted |
| Code: | .---------------------.---------------------.---------------------.
| 457 34 6 | 2 9 1 | 8 347 345 |
| 8 1239 123 | 5 7 4 | 12 139 6 |
| 14579 1249 127 | 8 3 6 | 127 1479 245 |
:---------------------+---------------------+---------------------:
| 14 7 12 | 6 28 3 | 9 5 48 |
| 3 24 5 | 1 28 9 | 6 48 7 |
| 6 8 9 | 4 5 7 | 3 2 1 |
:---------------------+---------------------+---------------------:
| 179 6 8 | 379 4 5 | 127 137 23 |
| 2 5 37 | 37 1 8 | 4 6 9 |
| 179 139 4 | 379 6 2 | 5 1378 38 |
'---------------------'---------------------'---------------------' |
Ted, who knows, maybe I did something wrong, but to avoid the deadly pattern r2c3 must be = 3 or r3c3 must be = 7 or r3c7 must be = 7. The first and third possibilities led to invalid solutions, so I solved r3c3 = 7. As I type this I haven't yet finished the puzzle.
| Quote: | | These xy-chains maybe underestimated, but it solves this grid in one fell swoop. Nevertheless i like these chains, they can be a powerful tool to break the puzzle wide open. |
They certainly can. I don't use them that often, but much of the time there's an XY-Chain when Medusa looks like a good possibility. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Thu Jun 26, 2008 9:06 pm Post subject: |
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| Code: | +-------------------+-------------------+-------------------+
| 457 34f 6 | 2 9 1 | 8 347 -345 |
| 8 1239 123 | 5 7 4 | 12 139 6 |
| 14579 1249 127 | 8 3 6 | 127 1479 245 |
+-------------------+-------------------+-------------------+
| 14 7 12 | 6 28 3 | 9 5 48b |
| 3 24e 5 | 1 28d 9 | 6 48c 7 |
| 6 8 9 | 4 5 7 | 3 2 1 |
+-------------------+-------------------+-------------------+
| 179 6 8 | 379 4 5 | 127 137 23 |
| 2 5 37 | 37 1 8 | 4 6 9 |
| 179 1-39 4 | 379 6 2 | 5 1378 38a |
+-------------------+-------------------+-------------------+ |
There is a similar chain (abcdef) that starts to make sense for me:
In R5 e and f sort of collapse into <48> and the chain looks like 38 48 48 48 34 which is an XY-wing with coloring on the pivot.
Keith |
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