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A bit tough.

 
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.

PostPosted: Tue Feb 01, 2011 5:37 am    Post subject: A bit tough. Reply with quote

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

PostPosted: Tue Feb 01, 2011 7:30 am    Post subject: Reply with quote

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

PostPosted: Tue Feb 01, 2011 10:47 am    Post subject: Reply with quote

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 Exclamation
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
||
(9)r2c5 - (9=2)r4c5 ; r9c5<>2
||
(9)r2c5 - (1)r2c5=r2c1 - r3c2=r9c2 ; r9c5<>1
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keith



Joined: 19 Sep 2005
Posts: 3341
Location: near Detroit, Michigan, USA

PostPosted: Tue Feb 01, 2011 1:14 pm    Post subject: Reply with quote

Coloring on 1 (nothing fancy) and an XY-wing will do it.

Keith
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