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Free Press October 20, 2011 (Thursday)

 
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Oct 22, 2011 1:26 am    Post subject: Free Press October 20, 2011 (Thursday) Reply with quote
Code:
Puzzle: FP102011
+-------+-------+-------+
| . . . | . . 5 | . . . |
| 2 . 7 | 3 6 . | . . 8 |
| . 9 . | . . 7 | . 4 . |
+-------+-------+-------+
| . 4 . | . 8 . | . 3 . |
| 8 . 9 | . . . | 2 . 4 |
| . 5 . | . 4 . | . . . |
+-------+-------+-------+
| . 6 . | 5 . . | . 1 . |
| 5 . . | . 9 . | 7 . 3 |
| . . . | 2 . . | . . . |
+-------+-------+-------+

Keith
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Sat Oct 22, 2011 3:18 am    Post subject: Reply with quote
Code:
 *-----------------------------------------------------------*
 | 4     38    368   | 9     1     5     | 36    2     7     |
 | 2     1     7     | 3     6     4     | 59    59    8     |
 |*36    9     5     | 8     2     7     | 136   4    *16    |
 |-------------------+-------------------+-------------------|
 | 16    4     26    | 7     8     29    | 159   3     159   |
 | 8     7     9     | 1     5     3     | 2     6     4     |
 |*13    5     23    | 6     4     29    | 8     7     9-1   |
 |-------------------+-------------------+-------------------|
 | 79    6     34    | 5     37    8     | 49    1     2     |
 | 5     2     1     | 4     9     6     | 7     8     3     |
 | 79    38    348   | 2     37    1     | 4569  59    569   |
 *-----------------------------------------------------------*
xy-wing
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Oct 22, 2011 3:51 am    Post subject: Reply with quote
Yes,

There's an unhelpful 59 UR in there too.

Keith
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Sat Oct 22, 2011 4:33 am    Post subject: Reply with quote
I wish that I could say that I found this gem manually.

Code:
 +---------------------------------------------------------------+
 |  4    *38   *38+6  |  9     1     5     |  3-6    2     7     |
 |  2     1     7     |  3     6     4     | *59    *59    8     |
 |  36    9     5     |  8     2     7     |  136    4     16    |
 |--------------------+--------------------+---------------------|
 |  16    4     26    |  7     8     29    |  159    3     159   |
 |  8     7     9     |  1     5     3     |  2      6     4     |
 |  13    5     23    |  6     4     29    |  8      7     19    |
 |--------------------+--------------------+---------------------|
 |  79    6     34    |  5     37    8     |  49     1     2     |
 |  5     2     1     |  4     9     6     |  7      8     3     |
 |  79   *38   *38+4  |  2     37    1     | *59+46 *59    569   |
 +---------------------------------------------------------------+
 # 36 eliminations remain

 UR38[(6)r1c3=(4)r9c3] - UR59[(4=6)r9c7]  =>  r1c7<>6


Last edited by daj95376 on Sat Oct 22, 2011 4:33 am; edited 1 time in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Oct 22, 2011 4:33 am    Post subject: Reply with quote
I used the same XY-Wing.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Oct 22, 2011 5:26 am    Post subject: Reply with quote
daj95376 wrote:
I wish that I could say that I found this gem manually.

Code:
 +---------------------------------------------------------------+
 |  4    *38   *38+6  |  9     1     5     |  3-6    2     7     |
 |  2     1     7     |  3     6     4     | *59    *59    8     |
 |  36    9     5     |  8     2     7     |  136    4     16    |
 |--------------------+--------------------+---------------------|
 |  16    4     26    |  7     8     29    |  159    3     159   |
 |  8     7     9     |  1     5     3     |  2      6     4     |
 |  13    5     23    |  6     4     29    |  8      7     19    |
 |--------------------+--------------------+---------------------|
 |  79    6     34    |  5     37    8     |  49     1     2     |
 |  5     2     1     |  4     9     6     |  7      8     3     |
 |  79   *38   *38+4  |  2     37    1     | *59+46 *59    569   |
 +---------------------------------------------------------------+
 # 36 eliminations remain

 UR38[(6)r1c3=(4)r9c3] - UR59[(4=6)r9c7]  =>  r1c7<>6

Danny,

Nice find!

I was on a different path of looking for the DP on the bottom floor, 79 - 34 - 37 - 49 when I noticed the XY-wing.

Keith
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Sat Oct 22, 2011 12:50 pm    Post subject: Reply with quote
Keith, I was also looking for DPs manually when I noticed the UR Type 1 and the UR Type 4 ... but not their connection. Finally, I gave up and ran the puzzle through my solver. You don't want to know the words I called myself when it popped out the connection between the two URs. _ Laughing _

The connection between the URs doesn't become apparent (to me) until the grid is organized with the extra candidates separate from the UR candidates. Besides, the UR Type 4 was misleading because I wanted to eliminate the 3s.

Regards, Danny
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
PostPosted: Sat Oct 22, 2011 4:11 pm    Post subject: Free Press October 20, 2011(Thursday) Reply with quote
The W-Wing 16 with strong link 1 in col 7; r3c1<>6 solves it as well.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Thu Oct 27, 2011 10:16 pm    Post subject: Reply with quote
Marty,

Take a look at the original puzzle.

There is a naked single:
R2C2 must be <1>.

There are also hidden singles:
R2C6 is the only square in row 2 that can be <4>.
R8C2 is the only square in column 2 that can be <2>.
R3C3 is the only square in column 3 that can be <5>.
R5C5 is the only square in column 5 that can be <5>.

Sudoku Susser calls Naked Singles "Forced", and calls Hidden Singles "Pinned".

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Fri Oct 28, 2011 1:39 am    Post subject: Reply with quote
I did the puzzle on Draw/Play and clicked Auto sweep after doing the standard cross-hatching and got this.

Code:

+------------------+----------------+------------------+
| 1346  138  13468 | 1489 12  5     | 1369  2679 12679 |
| 2     1    7     | 3    6   149   | 159   59   8     |
| 136   9    5     | 18   12  7     | 136   4    126   |
+------------------+----------------+------------------+
| 167   4    126   | 1679 8   1269  | 1569  3    15679 |
| 8     137  9     | 167  5   136   | 2     67   4     |
| 1367  5    1236  | 1679 4   12369 | 1689  6789 1679  |
+------------------+----------------+------------------+
| 3479  6    2348  | 5    37  348   | 489   1    29    |
| 5     128  1248  | 1468 9   1468  | 7     268  3     |
| 13479 1378 1348  | 2    137 13468 | 45689 5689 569   |
+------------------+----------------+------------------+

Play this puzzle online at the Daily Sudoku site

I suppose this illustrates the Naked Single. (It's better illustrated on the Draw/Play grid where it shows as a pencil mark, not a solved cell). In doing this with pencil and paper I'd just write 1 in r2c2 and move on. The concept of Naked Single would never occur to me and I don't see how I would use it.
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