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Feb 9 DB

 
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS

PostPosted: Sat Feb 09, 2008 1:20 pm    Post subject: Feb 9 DB Reply with quote

The Feb 9 DB opens with an x-wing (-4) followed by an xy-wing (-2).
Bingo!

Earl


Code:

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

Play this puzzle online at the Daily Sudoku site
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sat Feb 09, 2008 5:56 pm    Post subject: Reply with quote

I search for X-Wings only as a last resort. An XY-Wing, perhaps the same as yours, since the pincers were 2, plus a couple of ERs did the trick.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Sat Feb 09, 2008 8:30 pm    Post subject: Reply with quote

All this really needs is an XY-wing (and there is more than one) to make an elimination in B1 or B2.

There is a Unique Rectangle <68> that is not needed.

(I did make an X-wing elimination when solving with pencil and paper, but I take the moves as they come, not when I am certain I have exhausted all the "basic" moves.)

Here is the crunch point:
Code:
+----------------+----------------+----------------+
| 5    8    26   | 27   9    3    | 4    1    67   |
| 37   4    23   | 5    1    6    | 27   8    9    |
| 67   1    9    | 4    8    27   | 267  3    5    |
+----------------+----------------+----------------+
| 34   257  1    | 279  6    257  | 3578 579  478  |
| 9    57   36   | 1    4    8    | 3567 567  2    |
| 46   257  8    | 279  3    257  | 1    5679 467  |
+----------------+----------------+----------------+
| 1    3    4    | 68   2    9    | 5678 567  678  |
| 8    6    5    | 3    7    4    | 9    2    1    |
| 2    9    7    | 68   5    1    | 68   4    3    |
+----------------+----------------+----------------+

I count three XY-wings.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sun Feb 10, 2008 1:13 am    Post subject: Reply with quote

Quote:
I count three XY-wings.

Plus a W on 27 in boxes 23.
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