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Puzzle 11/07/25: A XY

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Mon Jul 25, 2011 3:47 pm    Post subject: Puzzle 11/07/25: A XY Reply with quote

A tight-knit solution when restricted to XY steps.

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

Play this puzzle online at the Daily Sudoku site
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Luke451



Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

PostPosted: Mon Jul 25, 2011 4:43 pm    Post subject: Reply with quote

How about just XY-"ish?"
Quote:
aur(12)r23c69[(8=5)r23c9]-r5c9=(5-1)r5c2=(1-8)r3c2=(8)r1c3 =>r1c9<>8
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Marty R.



Joined: 12 Feb 2006
Posts: 5180
Location: Rochester, NY, USA

PostPosted: Wed Jul 27, 2011 1:11 am    Post subject: Reply with quote

Four steps for me.

Type 4 UR (12); r23c9<>1
Type 4 UR (16); r4c39<>1
Potential DP boxes 23, 38-12-13-28; common outcome; r23c6=12
M-Wing (15); r4c3, r5c9<>5
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Wed Jul 27, 2011 1:30 pm    Post subject: Reply with quote

Danny, I worked on a "A tight-knit solution when restricted to XY steps' type solution but had no luck. However, I did find the same one-stepper as posted by Luke but with a different POV.

(1)r46c3=(1-5)r5c2=r5c9-aur(12)r23c69[(5)r3c9=(8)r23c9]-r1c9=(8-1)r1c3; r1c3<>1

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Wed Jul 27, 2011 3:12 pm    Post subject: Reply with quote

tlanglet wrote:
I worked on a "tight-knit solution" when restricted to XY steps' type solution but had no luck.

A 5-cell XY-Chain is present after basics. However, it doesn't proceed very far without the finned X-Wing. Together, they perform enough eliminations in r3c9 to expose the game-winning XY-Wing.

Code:
 after basics
 +--------------------------------------------------------------+
 |  2     3     18    |  5     7     6     |  14    9     148   |
 |  5     4     7     |  9     38    12    |  13    6     128   |
 |  6     18    9     |  34    348   12    |  135   7     1258  |
 |--------------------+--------------------+--------------------|
 |  8     7     156   |  2     14    9     |  145   3     1456  |
 |  3     15    2     |  14    6     7     |  9     8     145   |
 |  4     9     16    |  8     5     3     |  7     2     16    |
 |--------------------+--------------------+--------------------|
 |  7     56    35    |  36    2     4     |  8     1     9     |
 |  1     2     4     |  7     9     8     |  6     5     3     |
 |  9     68    38    |  136   13    5     |  2     4     7     |
 +--------------------------------------------------------------+
 # 41 eliminations remain

 r16\c39 finned  X-Wing                  <> 1    r23c9

XY-Chain: (8=3)r2c5 (=1)r2c7 (=2)r2c6 (=1)r3c6 (=8)r3c2  =>  r3c5<>8

 <18+5>  XY-Wing  r3c2/r3c9+r5c2         <> 5    r5c9


Note: a UR Type 4 is present ... but extraneous.
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