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Vanhegan extreme

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Fri Aug 17, 2012 3:43 pm    Post subject: Vanhegan extreme Reply with quote
Puzzle # 6-644191, rated 1.0.0.1.1. I've played a half-dozen moves and they just eliminate a candidate or two without opening anything up.

Code:

+----------------+--------------+-------------+
| 6   79    4    | 3    279 5   | 8   279  1  |
| 189 13789 357  | 29   6   19  | 4   279  25 |
| 19  2     157  | 8    179 4   | 579 3    6  |
+----------------+--------------+-------------+
| 7   136   1236 | 1269 5   139 | 12  8    4  |
| 128 18    9    | 4    12  7   | 6   5    3  |
| 5   4     1236 | 126  8   13  | 127 127  9  |
+----------------+--------------+-------------+
| 129 5     12   | 7    3   6   | 19  4    8  |
| 3   679   67   | 19   4   8   | 125 1269 25 |
| 4   169   8    | 5    19  2   | 3   16   7  |
+----------------+--------------+-------------+

Play this puzzle online at the Daily Sudoku site
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Fri Aug 17, 2012 4:26 pm    Post subject: Reply with quote
Marty,

There is an Empty Rectangle for r1c2<>9, but it doesn't contribute much until after you find the chain for r1c5<>7. Even so, there's still several steps remaining.

Code:
 ER -> r1c2<>9
 +-----------------------------------------------------------------------+
 |  6      79     4      |  3     *279    5      |  8      279    1      |
 |  189    1378-9 357    | *29     6     *19     |  4      279    25     |
 |  19     2      157    |  8     *179    4      |  579    3      6      |
 |-----------------------+-----------------------+-----------------------|
 |  7      136    1236   |  1269   5      139    |  12     8      4      |
 |  128    18     9      |  4      12     7      |  6      5      3      |
 |  5      4      1236   |  126    8      13     |  127    127    9      |
 |-----------------------+-----------------------+-----------------------|
 |  129    5      12     |  7      3      6      |  19     4      8      |
 |  3      679    67     |  19     4      8      |  125    1269   25     |
 |  4     *169    8      |  5     *19     2      |  3      16     7      |
 +-----------------------------------------------------------------------+
 # 68 eliminations remain

 (7=9)r1c2 - r23c1 = (9-2)r7c1 = r5c1 - r5c5 = (2)r1c5  =>  r1c5<>7
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Fri Aug 17, 2012 10:16 pm    Post subject: Reply with quote
Thanks Danny. Chains are a mixed blessing for me. They're effective, but the only way I can find them is with trial and error.

At any rate, after r1c5<>7, I used an XY-Wing (259), pivoted in r2c8 which made a direct elimination and more after a transport. I thought that would finish it off, but no, I then needed simple coloring on 1.

I know ratings don't always mean a lot, but this puzzle was more difficult than numerous others I've seen with more difficult ratings.
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