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Nov 7 DB

 
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
PostPosted: Sat Nov 07, 2009 3:23 pm    Post subject: Nov 7 DB Reply with quote
This Nov 7 DB almost stumpted me. I had to use three xy-chains to solve it. Any neat simple solutions out there?


Earl - of the chain gang

Code:

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

Play this puzzle online at the Daily Sudoku site

Last edited by Earl on Sat Nov 07, 2009 3:58 pm; edited 2 times in total
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Sat Nov 07, 2009 3:46 pm    Post subject: Reply with quote
I used:
Quote:
xyz-wing 456

oops! Embarassed I must have been seeing things not there
Code:

 *-----------------------------------------------------------*
 | 29    8     1     | 3     6     7     | 24   a49-5 *245   |
 | 7     4     6     |c59    58    2     | 1    b389   38    |
 | 29    3     5     | 49    48    1     | 7     6     28    |
 |-------------------+-------------------+-------------------|
 | 1     9     3     |d56    2     8     | 46   *45    7     |
 | 4     56    2     | 1     7     9     | 368   358   368-5 |
 | 8     56    7     | 456   45    3     | 9     2     1     |
 |-------------------+-------------------+-------------------|
 | 3     2     4     | 8     1     6     | 5     7     9     |
 | 5     7     8     | 2     9     4     | 36    1     36    |
 | 6     1     9     | 7     3     5     | 248   48    248   |
 *-----------------------------------------------------------*
(5)r1c9=(5-9)r1c8=(9)r2c8-(9=5)r2c4-(5)r4c4=(5)r4c8
 => r1c8,r5c9<>5;
singles


Last edited by arkietech on Sat Nov 07, 2009 7:59 pm; edited 1 time in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Nov 07, 2009 5:12 pm    Post subject: Reply with quote
I saw an XY-Wing on 564 but couldn't do anything with it. There was a Hidden UR on 36. That left me here:

Code:

+---------+----------+-------------+
| 29 8  1 | 3   6  7 | 24  459 245 |
| 7  4  6 | 59  58 2 | 1   389 38  |
| 29 3  5 | 49  48 1 | 7   6   28  |
+---------+----------+-------------+
| 1  9  3 | 56  2  8 | 46  45  7   |
| 4  56 2 | 1   7  9 | 68  358 358 |
| 8  56 7 | 456 45 3 | 9   2   1   |
+---------+----------+-------------+
| 3  2  4 | 8   1  6 | 5   7   9   |
| 5  7  8 | 2   9  4 | 3   1   6   |
| 6  1  9 | 7   3  5 | 248 48  248 |
+---------+----------+-------------+

Play this puzzle online at the Daily Sudoku site

For the 24 UR in boxes 3 and 9, either r1c9 =5 or one of r9c7 or r9c9 = 8. If either of those latter two = 8, then r4c8 must = 5 and that, along with the other pincer 5 in r1c9 completes it.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Sun Nov 08, 2009 6:48 pm    Post subject: Reply with quote
Marty R. wrote:
I saw an XY-Wing on 564 but couldn't do anything with it. There was a Hidden UR on 36. That left me here:

Code:

+---------+----------+-------------+
| 29 8  1 | 3   6  7 | 24  459 245 |
| 7  4  6 | 59  58 2 | 1   389 38  |
| 29 3  5 | 49  48 1 | 7   6   28  |
+---------+----------+-------------+
| 1  9  3 | 56  2  8 | 46  45  7   |
| 4  56 2 | 1   7  9 | 68  358 358 |
| 8  56 7 | 456 45 3 | 9   2   1   |
+---------+----------+-------------+
| 3  2  4 | 8   1  6 | 5   7   9   |
| 5  7  8 | 2   9  4 | 3   1   6   |
| 6  1  9 | 7   3  5 | 248 48  248 |
+---------+----------+-------------+

Play this puzzle online at the Daily Sudoku site

For the 24 UR in boxes 3 and 9, either r1c9 =5 or one of r9c7 or r9c9 = 8. If either of those latter two = 8, then r4c8 must = 5 and that, along with the other pincer 5 in r1c9 completes it.

Marty, I don't recall ever seeing anyone use a UR to establish a pincer arrangement to make a deletion. Fantastic move Exclamation

I also found this puzzle very challenging. I used three moves but all were very hard to find. All were chains found by extending the vertex of a potential xy-wing.

Ted
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Sun Nov 08, 2009 9:40 pm    Post subject: Reply with quote
Marty R. wrote:
I saw an XY-Wing on 564 but couldn't do anything with it. There was a Hidden UR on 36. That left me here:

Code:

.-----------.------------.----------------.
| 29  8   1 | 3    6   7 | 24   459  245  |
| 7   4   6 | 59   58  2 | 1    389  38   |
| 29  3   5 | 49   48  1 | 7    6    28   |
:-----------+------------+----------------:
| 1   9   3 | 56   2   8 | 46   45   7    |
| 4   56  2 | 1    7   9 | 368  358  3568 |
| 8   56  7 | 456  45  3 | 9    2    1    |
:-----------+------------+----------------:
| 3   2   4 | 8    1   6 | 5    7    9    |
| 5   7   8 | 2    9   4 | 36   1    36   |
| 6   1   9 | 7    3   5 | 248  48   248  |
'-----------'------------'----------------'



I don't get the hidden UR.

From here I would use a w-wing on 48 using the composite box three 24 48.
and the strong link box six 46 45.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sun Nov 08, 2009 11:31 pm    Post subject: Reply with quote
Quote:
I don't get the hidden UR.

The 3 is a strong link in c7 so the 6 is removed from r5c9.

Quote:
Marty, I don't recall ever seeing anyone use a UR to establish a pincer arrangement to make a deletion. Fantastic move

Thanks Ted, but I've seen it here a few times, that's the only reason I knew enough to use it.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon Nov 09, 2009 1:16 am    Post subject: Reply with quote
Marty found a strong inference on the 8's in r9c79 and the 5 in r1c9, because one of them has to be true in order to avoid the UR.

UR24[(5)r1c9 = (8)r9c79] - (8=4)r9c8 - (4=5)r4c8; r1c8 <> 5
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Mon Nov 09, 2009 1:38 am    Post subject: Reply with quote
Marty R. wrote:
Quote:
I don't get the hidden UR.

The 3 is a strong link in c7 so the 6 is removed from r5c9.


Thanks, I missed that.
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Mon Nov 09, 2009 1:41 am    Post subject: Reply with quote
storm_norm wrote:
Marty found a strong inference on the 8's in r9c79 and the 5 in r1c9, because one of them has to be true in order to avoid the UR.

UR24[(5)r1c9 = (8)r9c79] - (8=4)r9c8 - (4=5)r4c8; r1c8 <> 5


I had lost the 8 in r9c9 but still get the inference. Thanks.
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