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Vanhegan extreme

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Mon Oct 31, 2011 9:51 pm    Post subject: Vanhegan extreme Reply with quote
Puzzle 6-628691, rated 2.1.0.1.1.

I've made a couple of ineffective moves, but can't find another candidate to eliminate.

Code:

+------------+--------------+-----------------+
| 5 237 8    | 4   13  6    | 1237 127   9    |
| 9 234 234  | 58  7   1238 | 1235 1256  1236 |
| 6 237 1    | 9   35  23   | 4    257   8    |
+------------+--------------+-----------------+
| 1 9   67   | 3   2   5    | 8    4     67   |
| 3 256 2567 | 1   8   4    | 2579 25679 27   |
| 4 8   25   | 6   9   7    | 125  3     12   |
+------------+--------------+-----------------+
| 2 135 9    | 578 135 138  | 6    17    4    |
| 8 45  345  | 57  6   13   | 1239 1279  1237 |
| 7 136 36   | 2   4   9    | 13   8     5    |
+------------+--------------+-----------------+

Play this puzzle online at the Daily Sudoku site
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Tue Nov 01, 2011 5:49 am    Post subject: Reply with quote
Code:
 +-----------------------------------------------------------------------+
 |  5      237    8      |  4      13     6      | e1237   127    9      |
 |  9      234    234    |  58     7      1238   |  1235   1256  a1236   |
 |  6      237    1      |  9      35     23     |  4      257    8      |
 |-----------------------+-----------------------+-----------------------|
 |  1      9      67     |  3      2      5      |  8      4     c67     |
 |  3      256    2567   |  1      8      4      | d2579   25679 c27     |
 |  4      8      25     |  6      9      7      |  125    3      12     |
 |-----------------------+-----------------------+-----------------------|
 |  2      135    9      |  578    135    138    |  6      17     4      |
 |  8      45     345    |  57     6      13     |  1239   1279  b1237   |
 |  7      136    36     |  2      4      9      |  13     8      5      |
 +-----------------------------------------------------------------------+
 # 77 eliminations remain

 L-Wing: (3)r2c9 = (3-7)r8c9 = r45c9 - r5c7 = (7)r1c7  =>  r1c7<>3
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SudoQ



Joined: 02 Aug 2011
Posts: 127
PostPosted: Tue Nov 01, 2011 10:20 am    Post subject: Reply with quote
daj95376 wrote:
L-Wing: (3)r2c9 = (3-7)r8c9 = r45c9 - r5c7 = (7)r1c7 => r1c7<>3

If you scroll back to the position before the advanced steps, it looks like this:
5.84.6..99...7....6.19..4.819.32584.3..184...48.697.3.2.9...6.48...6....7..249.85
Already here there is a simple solution starting from the bivalue cell r7c8 (=> r1c7<>3).

/SudoQ
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Tue Nov 01, 2011 4:00 pm    Post subject: Reply with quote
SudoQ wrote:
If you scroll back to the position before the advanced steps, it looks like this:
5.84.6..99...7....6.19..4.819.32584.3..184...48.697.3.2.9...6.48...6....7..249.85

Marty did not post the original puzzle, and so I just started with his grid. Besides, that's the point where he was stuck.

SudoQ wrote:
Already here there is a simple solution starting from the bivalue cell r7c8 (=> r1c7<>3).

My solver searches for all chains within its capability of finding. This process sometimes consumes a lot of time and produces a lot of redundancy, so it's designed to save only the "simplest" solution for any elimination ... or combination of eliminations. There may well be other chains for (=> r1c7<>3), but I don't believe they are simpler than a known 3-SIS pattern based on two values.

Regards, Danny A. Jones
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Nov 01, 2011 5:45 pm    Post subject: Reply with quote
Thank you both for your suggestions. I can see the solution starting with the 17 cell but I don't understand L-Wings.
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SudoQ



Joined: 02 Aug 2011
Posts: 127
PostPosted: Tue Nov 01, 2011 5:54 pm    Post subject: Reply with quote
daj95376 wrote:
Marty did not post the original puzzle..

I know, and my intention was not to questioning your solution.
I just wanted to show an alternative, and that the original puzzle could be solved in one step.

daj95376 wrote:
... I don't believe they are simpler than a known 3-SIS pattern based on two values.

I can not judge which solution is considered to be the easiest.
I usually compare the number of steps and the number of 'used' cells.

/SudoQ
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Tue Nov 01, 2011 6:14 pm    Post subject: Reply with quote
SudoQ wrote:
I just wanted to show an alternative, and that the original puzzle could be solved in one step.

But you didn't ... and I was left wondering about your motives.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Nov 01, 2011 8:23 pm    Post subject: Reply with quote
Quote:
Marty did not post the original puzzle, and so I just started with his grid.

True, my laziness is showing. However, I did post the puzzle number if someone wanted to look at the starting grid.
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SudoQ



Joined: 02 Aug 2011
Posts: 127
PostPosted: Tue Nov 01, 2011 8:54 pm    Post subject: Reply with quote
daj95376 wrote:
But you didn't ...

Marty R. wrote:
I can see the solution starting with the 17 cell but I don't understand L-Wings.

Code:
r7c8=1/7
r7c8=1 => r9c7=3 => r1c7<>3
r7c8=7 => r12c8<>7 => r1c7(=7)<>3

/SudoQ
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