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Dec 19 DB

 
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
PostPosted: Sat Dec 19, 2009 3:24 pm    Post subject: Dec 19 DB Reply with quote
The December 19 DB has no apparent silver bullet. (Norm please prove me wrong). I had to shoot twice.

A Solution: A double finned x-wing eliminates the 2 in R7C9 and R8C8, then a skyscraper eliminates the 4 in R1C3.

Earl


Code:

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

Play this puzzle online at the Daily Sudoku site
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Dec 19, 2009 5:09 pm    Post subject: Reply with quote
Quote:
SS on 2; SS on 4.


Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Dec 19, 2009 6:08 pm    Post subject: Reply with quote
Similar, but the details are different. Simple coloring on 2 and a Kite on 4.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sun Dec 20, 2009 12:35 am    Post subject: Reply with quote
Quote:
Norm please prove me wrong

Code:
+---------------+------------+----------------+
| 6     9   14  | 5   3    2 | 8   7    1(4)  |
| 2(4)  3   8   | 1   9    7 | 6   24   5     |
| 7     12  5   | 68  68   4 | 3   9    12    |
+---------------+------------+----------------+
| 9     5   147 | 26  267  8 | 12  346  36(4) |
| 3     6   2   | 4   1    5 | 7   8    9     |
| 8(4)  18  147 | 9   267  3 | 12  5    6(4)  |
+---------------+------------+----------------+
| 5     7   3   | 28  4    1 | 9   26   268   |
| 1     28  6   | 7   5    9 | 4   23   238   |
| 28    4   9   | 3   28   6 | 5   1    7     |
+---------------+------------+----------------+

look at the arrangement of 4's in the grid. if the 4 in r4c9 is false, then the skyscraper on 4's exists in columns 1 and 9.
(4)r1c9 = (4)r6c9 - (4)r6c1 - (1)r1c1
and this would eliminate the 4 in r2c8 right?
so what happens when the skyscraper is false and the 4 is true in r4c9?
this triggers the kite on 2 via the 3's.
red is the kite on 2's

(4-3)r4c9 = (3)r4c8 - (3=2)r8c8 - (2)r8c2 = (2)r3c2 - (2)r3c9 = (2)r2c8

either way, the 4 in r2c8 can't exist.



[(4)r1c9 = (4)r6c9 - (4)r6c1 - (1)r1c1] = (4-3)r4c9 = (3)r4c8 - (3=2)r8c8 - (2)r8c2 = (2)r3c2 - (2)r3c9 = (2)r2c8; r2c8 <> 4
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