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Puzzle 10/10/19: C XY

 
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Tue Oct 19, 2010 4:07 am    Post subject: Puzzle 10/10/19: C XY Reply with quote

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

Play this puzzle online at the Daily Sudoku site
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Tue Oct 19, 2010 5:44 pm    Post subject: Reply with quote

Two steps...
Quote:
kite(4) r7, c3 ; r3c9<>4
m-wing-like with 3-cell-xy SL(79) instead of bivalue ; (7=4)r2c1-(4=3)r3c3-(3=9)r4c3 - r4c1=(9-7)r8c1=r9c3 ; r1c3<>7

With hindsight, the last move can be played after basics with a one-step '"almost" play that essentially combines the contradiction in 4s
Code:
fin (9)r3c3 - (9=4)r3c9 - r79c9=r9c8 - r9c3=r7c1 - (4=7)r2c1
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Marty R.



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

PostPosted: Wed Oct 20, 2010 4:38 am    Post subject: Reply with quote

Four moves here.

Multi-coloring (4)
X-Wing (7)
XYZ-Wing (238)
XY-Chain, r4c1<>9
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Wed Oct 20, 2010 2:09 pm    Post subject: Reply with quote

This puzzle offered a variety of non-productive steps; I was headed for a BBDB solution. On restarting, I found a two stepper............

skyscraper 4 r27c1; r3c9<>4

AW-wing (34)r3c3|r7c1 SL (3)r4c13 with fin (2)r7c1; r2c1<>4
If w-wing is true, r2c1<>4
||
If fin is true: (2)r7c1-(2=34)als:r3c13-(4)r2c1

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Wed Oct 20, 2010 2:58 pm    Post subject: Reply with quote

My solver used 3x steps to reduce this puzzle to something "cooperative". Otherwise, although the following is interesting, I never managed anything "prettier" than a cumbersome discontinuous network.

Code:
 after basics -- overlapping constraints
 +--------------------------------------------------------------+
 |  6     239   379   |  5     1     4     |  239   2378  789   |
 |  47    5     8     |  3     9     2     |  47    1     6     |
 |  39+24 1     39+4  |  8     6     7     |  5     234   49    |
 |--------------------+--------------------+--------------------|
 |  39    4     39    |  2     7     6     |  8     5     1     |
 |  8     6     1     |  9     3     5     |  47    47    2     |
 |  5     7     2     |  1     4     8     |  6     9     3     |
 |--------------------+--------------------+--------------------|
 |  234   238   5     |  7     28    9     |  1     6     48    |
 |  279   289   6     |  4     28    1     |  239   2378  5     |
 |  1     289   479   |  6     5     3     |  29    2478  4789  |
 +--------------------------------------------------------------+
 # 52 eliminations remain

 UR[(4)r3c13 = (2)r3c1]   -and-
 SL[(4)r3c13 = (4)r2c1]

Code:
(4)r2c1-UR[(4)r3c13=(2)r3c1]-(24=3)r7c1-r4c1=r4c3-(34=9)r3c3-(9=4)r3c9-r8c9=r7c1-(4)r2c1
        \                     /                    /
         -----------------------------------------
________________________________________________________________________________________

Yes, I know that I commited a network "sin" by assigning two different values to r7c1, but I didn't want to stop the chain after (=4)r3c9 eliminated the last <4> in [r7].
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Marty R.



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

PostPosted: Wed Oct 20, 2010 3:56 pm    Post subject: Reply with quote

Quote:
This puzzle offered a variety of non-productive steps

I'm offering up my assistance to anyone who asks, as this is my area of expertise. Cool
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