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Swordfish.

 
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Fri Mar 27, 2009 7:23 am    Post subject: Swordfish. Reply with quote
I used a hidden UR, 2 swordfish and a finned swordfish, as well as other easier stuff, on this one. I actually used 2 hidden URs but I don't know which ones mattered. Smile

Code:
. . 7|4 . 5|1 . .
. 3 .|7 . .|5 6 .
. . .|. 2 .|. 4 7
-----+-----+-----
. . .|. . 9|. . .
. 1 9|. . .|3 7 .
. . .|5 . .|. . .
-----+-----+-----
5 9 .|. 4 .|. . .
. 7 3|. . 6|. 8 .
. . 6|9 . 7|4 . .


This was generated using hobiwan's Hodoku.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Fri Mar 27, 2009 3:18 pm    Post subject: Reply with quote
I am not familiar with "hobiwan's Hodoku" but this was one monster puzzle for me. It took me 10 steps including two finned swordfish when I was stumped otherwise.

Overall, I used two URs, an ER, x-wing and finned x-wing, a swordfish plus two finned swordfish, w-wing and a xy-wing. I have no idea which steps directly contributed to the solution.

Great fun but exhausting!

Ted Smile
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Fri Mar 27, 2009 3:31 pm    Post subject: Reply with quote
tlanglet wrote:
I am not familiar with "hobiwan's Hodoku" but this was one monster puzzle for me. It took me 10 steps including two finned swordfish when I was stumped otherwise.


Hodoku is a solver/generator. Nice program, it seems to me.

http://hodoku.sourceforge.net/en/index.php
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Fri Mar 27, 2009 7:41 pm    Post subject: Reply with quote
Code:
.---------------------.---------------------.---------------------.
| 2689   268    7     | 4      689    5     | 1      239    2389  |
| 1289   3      4     | 7      189    18    | 5      6      289   |
| 1689   568    158   | 1368   2      138   | 89     4      7     |
:---------------------+---------------------+---------------------:
| 37     24568  258   | 12368  13678  9     | 268    12     1248  |
| 268    1      9     | 268    68     4     | 3      7      5     |
| 37     2468   28    | 5      13678  1238  | 2689   129    12489 |
:---------------------+---------------------+---------------------:
| 5      9      128   | 1238   4      1238  | 7      123    6     |
| 4      7      3     | 12     5      6     | 29     8      129   |
| 128    28     6     | 9      138    7     | 4      5      123   |
'---------------------'---------------------'---------------------'

UR {3,7} removes 3 from r46c5

(2)r2c1 = (2)r2c9 - (2)r9c9 = (2)r9c12 - (2)r7c3 = (2)r46c3; r5c1 <> 2

some dust settles...

the UR 28 in r19c12 says that neither the 8 in r1c5 nor the 2 in r1c8 can both be false or the deadly UR pattern is forced to exist in those four cells.
gives us this strong link UR28[(8)r1c5 = (2)r1c8]...

we can use that as follows

(1)r3c1 = (1)r3c6 - (1=8)r2c6 - UR28[(8)r1c5 = (2)r1c8] - (2)r2c9 = (2)r2c1; r2c1 <> 1
and the puzzle is solved.
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