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wapati
Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
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 Posted: Tue Feb 01, 2011 5:37 am Post subject: A bit tough. |
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I was fooling around with hudoku and got this fun one.
| Code: | 7 4 .|. . .|. . .
. . .|8 . 5|. . .
. . 9|. 3 .|. 6 .
-----+-----+-----
6 8 .|. . 1|7 . 3
3 . 2|. 5 .|1 . 6
9 . 1|3 . .|. 2 8
-----+-----+-----
. 6 .|. 4 .|3 . .
. . .|6 . 7|. . .
. . .|. . .|. 7 9 |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Feb 01, 2011 7:30 am Post subject: |
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here is a three step approach.
this is an almost x-wing in columns 4 and 5, makes some eliminations on 2.
#1...[x-wing(2)r49c45] = (2)r9c2 - (2=1)r3c2 - (1)r2c1 = (1-9)r2c5 = (9-2)r4c5 = (2)r4c4;
r1c4 and r2c5 and r7c4 are all not 2.
| Code: | +-----------------+-------------+----------------+
| 7 4 58 | 19 6 2 | 589 3 15 |
| 12 3 6 | 8 19 5 | 29 4 7 |
| 58 1(2) 9 | 7 3 4 | 258 6 15(2) |
+-----------------+-------------+----------------+
| 6 8 4 | 29 29 1 | 7 5 3 |
| 3 7 2 | 4 5 8 | 1 9 6 |
| 9 5 1 | 3 7 6 | 4 2 8 |
+-----------------+-------------+----------------+
| 158-2 6 7 | 15 4 9 | 3 18 5(2) |
| 1258 9 3 | 6 128 7 | 25 18 4 |
| 4 1(2) 58 | 125 128 3 | 6 7 9 |
+-----------------+-------------+----------------+
#2...skyscraper on 2; (2)r9c2 = (2)r3c2 - (2)r3c9 = (2)r7c9; r7c1 <> 2 |
then this nice xy-wing via the UR strong link
#3...(1=2)r9c2 - UR18[(2)r8c1 = (5)r7c1] - (5=1)r7c4; r9c45 <> 1 |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Tue Feb 01, 2011 10:47 am Post subject: |
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This is an interesting one (I think!) - but I am not sure how to write it in Eureka?
Consider the almost-remote-pair(12)...
| Code: | *-----------------------------------------------------------*
| 7 4 58 | 129 6 29 | 2589 3 125 |
|*12 3 6 | 8 *(129) 5 | (29) 4 7 |
| 58 *12 9 | 7 3 4 | 258 6 125 |
|-------------------+-------------------+-------------------|
| 6 8 4 | 29 (29) 1 | 7 5 3 |
| 3 7 2 | 4 5 8 | 1 9 6 |
| 9 5 1 | 3 7 6 | 4 2 8 |
|-------------------+-------------------+-------------------|
| 1258 6 7 | 1259 4 29 | 3 18 25 |
| 1258 9 3 | 6 128 7 | 25 18 4 |
| 4 *12 58 | 125 8-12 3 | 6 7 9 |
*-----------------------------------------------------------* |
Notice that there is a (29) bivalue in r2 which creates a (1=2) strong link in r2; and there is a (29)bivalue in c5 which similarly creates a (1=2)strong link in c5. Both strong links pivot at r2c5.
The effect is to "make good" the remote pair, eliminating (12) from r9c5 and solving the puzzle 
| Code: | remote-pair(12) with als
(1): (1=2)r9c2 - (2=1)r3c2 - (1=2)r2c1 - als(29=1)r2c57 ; r9c5<>1
(2): (2=1)r9c2 - (1=2)r3c2 - (2=1)r2c1 - als(1=29)r24c5 ; r9c5<>2 |
[EDIT]
Looking further I can see a more conventional "almost" approach .. less attractive I think
| Code: | remote-pair(12) r9c2, r2c3, r2c1, r2c5 ; r9c5<>12=8
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(9)r2c5 - (9=2)r4c5 ; r9c5<>2
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(9)r2c5 - (1)r2c5=r2c1 - r3c2=r9c2 ; r9c5<>1 |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Feb 01, 2011 1:14 pm Post subject: |
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Coloring on 1 (nothing fancy) and an XY-wing will do it.
Keith |
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