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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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 Posted: Tue Sep 30, 2008 4:24 pm Post subject: Great Vanhagen Fiendish Sept 29 |
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For me, this was a fun, many step (8+) puzzle using various VH techniques and a forcing chain to finish it off.
| Code: |
*-----------*
|.1.|4.9|8..|
|.5.|...|.64|
|4..|.3.|...|
|---+---+---|
|2..|.6.|..1|
|..4|7.2|5..|
|5..|.9.|..7|
|---+---+---|
|...|.4.|..8|
|64.|...|.7.|
|..8|6.7|.3.|
*-----------* |
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Sep 30, 2008 5:52 pm Post subject: |
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Phew, quite a few steps. At least I didn't need a forcing chain in this one:
- coloring (1 and 5)
- swordfish (2 and 9)
- xy-wing (18-15-58 boxes 2 and 5)
- (generalized) m-wing (9)r3c9=r8c7 ( via (2) in row 8 ) here:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 7 1 6 | 4 25 9 | 8 25 3 |
| 39 5 23 | 12 7 8 | 19 6 4 |
| 4 8 29 | 15 3 6 | 7 15 29* |
+--------------------------+--------------------------+--------------------------+
| 2 79 79 | 58 6 45 | 3 48 1 |
| 8 3 4 | 7 1 2 | 5 9 6 |
| 5 6 1 | 38 9 34 | 2 48 7 |
+--------------------------+--------------------------+--------------------------+
| 39 27 357 | 359 4 135 | 6 12 8 |
| 6 4 35 | 2359# 8 135 | 19* 7 25# |
| 1 29 8 | 6 25 7 | 4 3 59 |
+--------------------------+--------------------------+--------------------------+
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There were a few URs as well but somehow they must have been redundant (same elimination achieved by other means it seems) |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Sep 30, 2008 9:29 pm Post subject: |
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| Quote: | | - swordfish (2 and 9) |
I don't think I've used one in over two years. Too much work for too little return. Is there something about certain grids that tell you to look for them? Is there a non-tedious way to look for them? |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Sep 30, 2008 10:31 pm Post subject: |
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| Marty R. wrote: | | Quote: | | - swordfish (2 and 9) |
I don't think I've used one in over two years. Too much work for too little return. Is there something about certain grids that tell you to look for them? Is there a non-tedious way to look for them? |
Swordfish are pretty low on my list of priorities when looking for "advanced" moves in a grid. But since I use the same tool ("nataraj diagrams" (c) Keith) for x-wing, kite, skyscraper, turbot fish, w-wing, m-wing, swordfish, ER and finned species they seem to turn up more often. Like in this puzzle: the xy-wing is present in the same grid as the swordfish, but xy-wing requires a completely different search pattern, so I only dicovered it later...
The different stages, for me, are:
1 - basic moves: I always try those first
1a: check for URs whenever possible (but keep the results in reserve, "use only as directed", cf. "making a puzzle harder by removing candidates")
2 - coloring eliminations visible by looking at the strong links (x-wing, kite, skyscraper, multi-coloring)
3 - w-wing, m-wing: look at strong links in combination with bi-value cells
4 - swordfish, jellyfish, ER and finned x-wing: look more closely at cells outside the strong links, at patterns that "might be"
if there are very few multi-valued cells or if all else fails or to give my brain a break  -> look for xy(z) wing.
use Medusa/GEM as last resort if all else fails.
if still clueless: turn to this forum and complain 
P.S. and, yes, there is something that tells me to look for them: the "Times" super fiendish can be solved by swordfish if x-wing is not enough. It says so in their intro ...  (and I do these fairly often) |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Sep 30, 2008 11:47 pm Post subject: |
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I had:
a finned x-wing on 1,
two skyscrapers on 5 and 9,
two URs on <48> and <79>,
an xy-wing on <129> with the <2> transported three times for deletions (which I suspect was the same as coloring on <2> by Nataraj),
a swordfish on 9,
and a forcing chain similar to the m-wing used by Nataraj: sequence a-b-c-d as shown. If r8c9=5 then r8c4=2 (strong link on 2) then r8c7=9(strong link on 9) then r9c9=5 thus r8c9 <>5.
| Code: |
+--------------------------+--------------------------+--------------------------+
| 7 1 6 | 4 25 9 | 8 25 3 |
| 39 5 23 | 12 7 8 | 19 6 4 |
| 4 8 29 | 15 3 6 | 7 15 29 |
+--------------------------+--------------------------+--------------------------+
| 2 79 79 | 58 6 45 | 3 48 1 |
| 8 3 4 | 7 1 2 | 5 9 6 |
| 5 6 1 | 38 9 34 | 2 48 7 |
+--------------------------+--------------------------+--------------------------+
| 39 27 357 | 359 4 135 | 6 12 8 |
| 6 4 35 | 2359b 8 135 | 19c 7 25a |
| 1 29 8 | 6 25 7 | 4 3 59d |
+--------------------------+--------------------------+--------------------------+
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I need to improve my m-wing searching technique as forcing chains are not my bag.
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Oct 01, 2008 12:45 am Post subject: |
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| Thanks nataraj. |
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