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Puzzle 10/10/15: C XY

 
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Fri Oct 15, 2010 4:31 am    Post subject: Puzzle 10/10/15: C XY Reply with quote

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

Play this puzzle online at the Daily Sudoku site
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peterj



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

PostPosted: Fri Oct 15, 2010 8:07 am    Post subject: Reply with quote

A wing
Quote:
w-wing(79) with pseudocell ; (7=6)r3c1-(6=9)r6c1 - r6c5=r1c5 - (9=7)r1c7 ; r3c7<>7
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Fri Oct 15, 2010 8:54 am    Post subject: Reply with quote

Hmmm! I've had my reservations about the use of pseudo-cells, but I previously accepted them as harmless. With Peter's solution, even though I understand his intent, I'm not so sure that every use of a pseudo-cell is harmless.

Code:
w-wing(79) with pseudocell ; (7=6)r3c1-(6=9)r6c1 - r6c5=r1c5 - (9=7)r1c7 ; r3c7<>7
                --------->   *******************

The pseudo-cell exists in [c1]. One end is in [r3] and sees the elimination cell. The other end is in [r6] and sees one end of the intermediate strong link needed for the W-Wing. I'm not comfortable with calling it a "wing". With his use of a pseudo-cell, a 6-cell XY-Chain could be described as an XY-Wing with 3x pseudo-cells. That's a far stretch of the concept, but it still exists.

Code:
 +--------------------------------------------------------------+
 |  4     37    236   |  8    d2679  1679  | e79    5     12    |
 |  17    9     12    |  5     27    4     |  3     6     8     |
 | a67    5     8     |  267   3     1679  |  9-7   4     12    |
 |--------------------+--------------------+--------------------|
 |  2     37    346   |  467   67    5     |  1     8     9     |
 |  579   1     45    |  247   8     79    |  24    3     6     |
 | b69    8     46    |  1    c269   3     |  24    7     5     |
 |--------------------+--------------------+--------------------|
 |  8     4     9     |  3     5     2     |  6     1     7     |
 |  3     6     7     |  9     1     8     |  5     2     4     |
 |  15    2     15    |  67    4     67    |  8     9     3     |
 +--------------------------------------------------------------+
 # 44 eliminations remain

To me, a pseudo-cell is two cells that act as one in a house/unit. Typically in a UR scenario.

Comments!
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peterj



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

PostPosted: Fri Oct 15, 2010 9:36 am    Post subject: Reply with quote

Danny, so first off I am definitely not wedded to the term 'pseudocell' and don't have a dogmatic view on insisting such a move is a 'wing'! I am just trying to communicate my solution.
I started using it because I noticed in this forum that people often described short xy-chains as 'xy-wings with pseudocell' and use terms like 'extended' or 'transport' as a qualifier on a pattern name.
I have since used it quite frequently on m-wing and w-wings where I have seen the 'pattern' but then one end needs a bit of work to fit the template! I feel that it describes how the solver sees his/her solution and, for a learner coming to this forum as I was/am, it might be an aid to starting to look for more complex chains. That's certainly how I started!
I agree you could apply such terms in ridiculous situations but I am not sure your xy-chain example is fair. If something has a formal name accepted by the community it should be used. AFAIK the move above does not have a formal name (other than a generic 'chain' or 'AIC') and so calling it a 'w-wing using pseudocell' is intended as a description. I suppose it's indicative rather than normative.
I think the problem becomes where to draw the line - is a pseudocell in a block somehow acceptable but not if well separated in a row or a column? I suppose one could perhaps limit the term to URs. Ultimately the only robust approach is to limit oneself to formally agreed names (by who?) and AIC or SIS descriptions - which I think would be a shame.
Interesting debate.
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tlanglet



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

PostPosted: Fri Oct 15, 2010 2:35 pm    Post subject: Reply with quote

Another "almost".

Quote:
AXY-wing 67-9 vertex (67)r4c5, pincers (69)r1c5 & (79)r5c6 with fin (27)r1c5; r3c6<>9
[xy-wing(67-9)=(27)ls:r1c5|r2c5]-(27=6)r3c4-(6=7)r3c1-(7=9)r3c7;

Ted
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tlanglet



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

PostPosted: Fri Oct 15, 2010 3:02 pm    Post subject: Reply with quote

I agree with the comments already offered by Peter. Recently I responded here to a request by Marty on the definition of "pseudocell" and specifically questioned if it included more than two cells.

I do not have a strong leaning on the issue, but my preference is to restrict usage to ADPs and to one cell extensions (for a total of two cells) for general bivalue patterns; "transport" or "extend" would be used for multiple steps/cells.

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Fri Oct 15, 2010 6:31 pm    Post subject: Reply with quote

Please forget that I mentioned the topic.

We'll leave it up to the individual to decide if the use of pseudo-cell seems appropriate in a post.

Regards, Danny
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Marty R.



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

PostPosted: Sat Oct 16, 2010 4:31 am    Post subject: Reply with quote

I played the Type 3 UR (15) with 27 pseudo cell, X-Wing (1) and XY-Wing (679), flightless with pincer transport.
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