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Set F Puzzle 18

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Sat Dec 06, 2008 7:08 am    Post subject: Set F Puzzle 18 Reply with quote

Enjoy the basics.

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

Play this puzzle online at the Daily Sudoku site
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Sun Dec 07, 2008 1:40 pm    Post subject: Reply with quote

Code:
 +-----------------------------------------------------------------------+
 |  6      4      1239   |  29     7      15     |  39     59     8      |
 |  8      5      29     |  4      26     3      |  679    1      679    |
 |  139    139    7      |  69     8      15     |  3469   4569   2      |
 |-----------------------+-----------------------+-----------------------|
 |  47     8      59     |  1      49     6      |  2      3      4579   |
 |  2      139    1359   |  7      49     8      |  1469   469    14569  |
 |  47     6      19     |  5      3      2      |  1479   8      1479   |
 |-----------------------+-----------------------+-----------------------|
 |  139    1379   6      |  8      12     79     |  5      249    149    |
 |  159    2      8      |  3      156    4      |  169    7      169    |
 |  159    179    4      |  26     1256   79     |  8      269    3      |
 +-----------------------------------------------------------------------+
 # 84 eliminations remain

         XY-Wing  [r2c5]/[r2c3]+[r3c4]   <> 9    [r3c12]
         ...
         XY-Wing  [r9c4]/[r3c4]+[r9c8]   <> 9    [r3c8]
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Dec 08, 2008 2:41 am    Post subject: Reply with quote

I was hoping this situation would come up in one of these puzzles.

we have seen how a hinged/grouped link within a box can be used to form a w-wing.

you can use that same inference in a row or a column

as shown below.
this image is the state of the puzzle after a xy-wing {2,6,9} and some basics.

the black lines represent the links on 9 and the red lines are the pincers from the 6's

notice that the 9 in r3c8 is strongly linked to the group of 9's in col 8 in box 9. (they both cannot be false) this makes it possible to connect the w-wing with the {6,9} cells.

you have the w-wing {6,9} via the strong link between the 9 in r3c8 and the group of 9's in r79c8.

(6=9)r8c7 - (9)r79c8 = (9)r3c8 - (9=6)r4c4; r4c7 <> 6
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