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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Mon Jun 22, 2009 5:59 pm    Post subject: BB for today Reply with quote
If you like X-wings, this one is for you.
Code:

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

Play this puzzle online at the Daily Sudoku site

What is this called? After basics:
Code:
+-------------------+-------------------+-------------------+
| 2     67    3     | 467   8     1     | 9     47    5     |
| 1     4     789XH | 5     79    2     | 78X   6     3     |
| 5     6789 67-89  | 467   3679  39    |247-8  2478G 1     |
+-------------------+-------------------+-------------------+
| 3     5     479   | 8     279   6     | 24    1     27    |
| 8     179   1479  | 127   12579 59    | 2345  234   6     |
| 6     2     17    | 3     157   4     | 58    9     78    |
+-------------------+-------------------+-------------------+
| 9     168  126-8  | 126   35    358   |2367-8 2378  4     |
| 4     3     1268X | 9     126   7     | 268X  5     28F   |
| 7     68    5     | 26    4     38    | 1     238   9     |
+-------------------+-------------------+-------------------+

Either the X-wing on <8> is true, or the fin F is true. Either way, we can eliminate <8> from R7C7. A finned X-wing.

Now, if F is true, so is G, and we can eliminate <8> in R3C7. If G is true so is H, and we can eliminate <8> in R37C3.

Keith
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Mon Jun 22, 2009 6:17 pm    Post subject: Reply with quote
Keith,

I like it! Very Happy I have not seen this before -- but I will start looking.

Nice find!
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Mon Jun 22, 2009 6:28 pm    Post subject: Reply with quote
Dan,

Thank you. I now see there is a swordfish that makes the same eliminations.

Keith
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Mon Jun 22, 2009 6:59 pm    Post subject: Reply with quote
Keith,

Shucks! Crying or Very sad I thought you had something.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Mon Jun 22, 2009 7:16 pm    Post subject: Reply with quote
arkietech wrote:
Keith,

Shucks! Crying or Very sad I thought you had something.


Not really. The swordfish involves other cells (in R6) than the ones I used. What I am doing (and I have seen this before) is grouped coloring starting from the fin cell.

I thought it might be a kraken franken something. When I see the examples for these, I understand them, but I have never found one myself.

Keith
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Mon Jun 22, 2009 7:20 pm    Post subject: Re: BB for today Reply with quote
keith wrote:
If you like X-wings, this one is for you.
Play this puzzle online at the Daily Sudoku site

What is this called? After basics:
Code:
+-------------------+-------------------+-------------------+
| 2     67    3     | 467   8     1     | 9     47    5     |
| 1     4     789XH | 5     79    2     | 78X   6     3     |
| 5     6789 67-89  | 467   3679  39    |247-8  2478G 1     |
+-------------------+-------------------+-------------------+
| 3     5     479   | 8     279   6     | 24    1     27    |
| 8     179   1479  | 127   12579 59    | 2345  234   6     |
| 6     2     17    | 3     157   4     | 58    9     78    |
+-------------------+-------------------+-------------------+
| 9     168  126-8  | 126   35    358   |2367-8 2378  4     |
| 4     3     1268X | 9     126   7     | 268X  5     28F   |
| 7     68    5     | 26    4     38    | 1     238   9     |
+-------------------+-------------------+-------------------+

Either the X-wing on <8> is true, or the fin F is true. Either way, we can eliminate <8> from R7C7. A finned X-wing.

Now, if F is true, so is G, and we can eliminate <8> in R3C7. If G is true so is H, and we can eliminate <8> in R37C3.

Keith

Keith, this is what I have been calling a Kraken x-wing based on some interactions with Wapati. I believe that the formal definition of a Kraken x-wing assumes the fin is in a separate box, but I use this approach to find additional deletions even if the fin is in the box of one of the corners making the x-wing; the logic is the same. In fact, I used this exact process for my first move on this puzzle.

It should also be noted that these four deletions are also deleted by the swordfish in r379c268, so the Kraken x-wing is not needed and it is generally more involved.

Ted
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