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Nov 23 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Mon Nov 22, 2010 11:02 pm    Post subject: Nov 23 VH Reply with quote

Three steps:-
1) UR 28 removes the 8's in BOX 7 row 8 opens
2) XY-Wing 58 25 28 removes 8 in r9c3 which opens onother
3) XY-Wing 58 57 78 eliminating 8 in r79c26 solves it.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Nov 23, 2010 1:20 am    Post subject: Reply with quote

Two steps for me: 258 XYZ wing centred on R8C3 which opens up a 578 XY wing centred on R9C3.
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Marty R.



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

PostPosted: Tue Nov 23, 2010 4:39 am    Post subject: Reply with quote

A W-Wing on 78s in boxes 28, connected by 7s in c3, r7c6<>8, was enough.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Tue Nov 23, 2010 11:42 am    Post subject: er solution Reply with quote

the strongly linked 7 s in row 7 and col 6 deny a 7 in r2c6 since this would deny any 7 to box A

Last edited by George Woods on Wed Nov 24, 2010 1:48 pm; edited 1 time in total
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yeoks



Joined: 16 May 2010
Posts: 33

PostPosted: Tue Nov 23, 2010 1:17 pm    Post subject: Reply with quote

A skyscraper (7) in columns 3 and 6 removes 7 from r7c1 and r9c4 and solves.
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tlanglet



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

PostPosted: Tue Nov 23, 2010 3:10 pm    Post subject: Reply with quote

Simple coloring on 7 is also a one step solution.

Another one step solution that may be of interest to some because it is a little different than the standard moves is an "almost or finned" xy-wing 5-78 with vertex (58)r7c2, pincers (78)r7c6 & (57)r9c3 plus the fin (8)r9c3.

Code after basics:
Code:

 *-----------------------------------------------------------*
 | 78    4     3     | 2     9     5     | 78    1     6     |
 | 5     168   178   | 678   4     78    | 3     9     2     |
 | 678   2     9     | 678   1     3     | 578   578   4     |
 |-------------------+-------------------+-------------------|
 | 28    3     28    | 1     7     6     | 9     4     5     |
 | 9     15    15    | 3     2     4     | 67    67    8     |
 | 4     7     6     | 5     8     9     | 1     2     3     |
 |-------------------+-------------------+-------------------|
 | 38-7 *58    4     | 9     6    *78    | 2     358   1     |
 | 2368  9     258   | 4     35    1     | 568   3568  7     |
 | 1     568  *57(8) | 78    35    2     | 4     3568  9     |
 *-----------------------------------------------------------*


Either the xy-wing is true (r9c3<>8) or the fin is true (r9c3=8)
If the xy-wing is true then the two pincers on 7 in r7c6 & r9c3 eliminate the 7 in r7c1;
If the fin in true then r9c3=8, r4c3<>8, then r4c1=8, then r1c1<>8=7 which eliminates the 7 in r7c1:
Thus, r7c1<>7 to complete the puzzle.

Ted
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Marty R.



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

PostPosted: Tue Nov 23, 2010 5:39 pm    Post subject: Re: er solution Reply with quote

George Woods wrote:
the strongly linked 7 s in row 7 and col 6 deny a 6 in r2c6 since this would deny any 7 to box A

George, I could have screwed up, but my basics had solved r4c6=6
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Marty R.



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

PostPosted: Tue Nov 23, 2010 6:06 pm    Post subject: Reply with quote

This is my post-basics grid:

Code:

+--------------+-----------+------------+
| 78   4   3   | 2   9  5  | 78  1    6 |
| 5    168 178 | 678 4  78 | 3   9    2 |
| 678  2   9   | 678 1  3  | 578 578  4 |
+--------------+-----------+------------+
| 28   3   28  | 1   7  6  | 9   4    5 |
| 9    15  15  | 3   2  4  | 67  67   8 |
| 4    7   6   | 5   8  9  | 1   2    3 |
+--------------+-----------+------------+
| 378  58  4   | 9   6  78 | 2   358  1 |
| 2368 9   258 | 4   35 1  | 568 3568 7 |
| 1    568 578 | 78  35 2  | 4   3568 9 |
+--------------+-----------+------------+

Play this puzzle online at the Daily Sudoku site
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prakash



Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA

PostPosted: Wed Nov 24, 2010 2:35 am    Post subject: Reply with quote

A finned X wing on 7s provides elimination similar to the skyscraper on 7.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Wed Nov 24, 2010 10:15 am    Post subject: er in A Reply with quote

marty wrote
George, I could have screwed up, but my basics had solved r4c6=6

My original said "deny a 6", but of course I should have written "deny a 7"

Sorry
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Ema Nymton



Joined: 17 Apr 2009
Posts: 89

PostPosted: Fri Nov 26, 2010 10:57 am    Post subject: Reply with quote

.

Basic has arrived here:

Code:

+--------------+-----------+------------+
| 78   4   3   | 2   9  5  | 78  1    6 |
| 5    168 178 | 678 4  78 | 3   9    2 |
| 678  2   9   | 678 1  3  | 578 578  4 |
+--------------+-----------+------------+
| 28   3   28  | 1   7  6  | 9   4    5 |
| 9    15  15  | 3   2  4  | 67  67   8 |
| 4    7   6   | 5   8  9  | 1   2    3 |
+--------------+-----------+------------+
| 378* 58  4   | 9   6  78 | 2   358  1 |
| 2368 9   258 | 4   35 1  | 568 3568 7 |
| 1    568 578 | 78  35 2  | 4   3568 9 |
+--------------+-----------+------------+


Draw/Play gives as Hint - r7c1 is '3'. Is it possible one can explain why?

Still trying to follow the reasoning of the puzzler.

Ema Nymton
.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Fri Nov 26, 2010 5:23 pm    Post subject: Reply with quote

Ema,

Form the position you posted there is an XYZ-wing 25-8 and then an XY-wing 5-78 that solve R7C2 as 8 and then R7C1 as 3.

Sudoku Susser is a very good tool to explain moves.

Best wishes,

Keith
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Sat Nov 27, 2010 11:16 pm    Post subject: Reply with quote

Regarding the Draw/Play hint of 3 at r7c1.

From the posted position,

Code:

+--------------+-----------+------------+
| 78   4   3   | 2   9  5  | 78  1    6 |
| 5    168 178 | 678 4  78 | 3   9    2 |
| 678  2   9   | 678 1  3  | 578 578  4 |
+--------------+-----------+------------+
| 28   3   28  | 1   7  6  | 9   4    5 |
| 9    15  15  | 3   2  4  | 67  67   8 |
| 4    7   6   | 5   8  9  | 1   2    3 |
+--------------+-----------+------------+
| 378* 58  4   | 9   6  78 | 2   358  1 |
| 2368 9   258 | 4   35 1  | 568 3568 7 |
| 1    568 578 | 78  35 2  | 4   3568 9 |
+--------------+-----------+------------+


There is a finned X-wing on 8's in columns 2 and 6 that eliminates
8 from R7C1 but produces no additional simple eliminations.

Follow that with an almost identical finned X-wing on 7's in columns
3 and 6 that eliminates 7 from R7C1, leaving you with R7C1=3.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Sun Nov 28, 2010 4:46 am    Post subject: Reply with quote

The conundrum is that draw/play supposedly only understands X-wings, XY-wings, and XYZ-wings as advanced moves.

With only those tools in the toolbox, I see no direct way from Ema's grid to R7C1 <3>.

Keith
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