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Puzzle 10/04/20 (A)

 
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Tue Apr 20, 2010 5:35 pm    Post subject: Puzzle 10/04/20 (A) Reply with quote
Code:
 +-----------------------+
 | . . . | 1 . . | . 9 7 |
 | . 1 . | . 5 9 | . 6 4 |
 | . . 7 | . . 3 | 8 . 1 |
 |-------+-------+-------|
 | 3 . . | . . 8 | . . . |
 | . 8 . | . 1 . | . . . |
 | . 5 6 | 3 . . | . 8 . |
 |-------+-------+-------|
 | . . 5 | . . . | 6 . . |
 | 8 3 . | . . 1 | . 7 . |
 | 6 9 1 | . . . | . . 8 |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
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Wendy W



Joined: 04 Feb 2008
Posts: 144
PostPosted: Tue Apr 20, 2010 10:40 pm    Post subject: Reply with quote
I got it in three steps:
XYZ (245), XY (247), XY (239)
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Wed Apr 21, 2010 2:41 pm    Post subject: Reply with quote
Here is another finned xy-wing very similar to the one recently posted by Mogulmeister for Danny's 10/04/19 (C) puzzle.

The code after basics.
Code:

 *--------------------------------------------------------------------*
 | 5      46     3      | 1      8      46     | 2      9      7      |
 | 2      1      8      | 7      5      9      | 3      6      4      |
 | 9      46     7      | 246    246    3      | 8      5      1      |
 |----------------------+----------------------+----------------------|
 | 3      27     249    | 24569  24679  8      | 1      24     2569   |
 | 47     8      249    | 24569  1      24567  | 4579  #234    2-3569 |
 | 1      5      6      | 3      2479   247    | 479    8     #29     |
 |----------------------+----------------------+----------------------|
 | 47     27     5      | 8      39     24     | 6      1     #39     |
 | 8      3      24     | 24569  2469   1      | 459    7      259    |
 | 6      9      1      | 245    2347   2457   | 45     2-34   8      |
 *--------------------------------------------------------------------*

Notice the finned xy-wing 2-39, marked #, with vertex 29 in r6c9 and fin 4 in r5c8.
A single chain using one of the variations illustrated by Danny is possible, but a two step explanation is preferred.
If the xy-wing is true then r5c9|r9c8<>3,
If the fin is true, then: (4)r5c8 - (4=7)r5c1 - (7=2)r4c2 - (2=4)r4c8; r5c8<>4, so the xy-wing is true.

Then, a xy-wing 2-47 with vertex in r4c2; r4c3|r5c7<>4 completes this puzzle.
Note that if this xy-wing had been used first, it would have deleted the fin for the other xy-wing. Luck of the draw........

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Apr 21, 2010 10:53 pm    Post subject: Reply with quote
This was a BBDB for me. Three XY-Wings, 26 UR implications and X-Wing.
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