There Was a Time: 04/23/13

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There Was a Time: 04/23/13

Postby daj95376 » Wed Apr 24, 2013 12:07 am

Code: Select all
 +-----------------------+
 | 1 . 4 | . . . | . . 6 |
 | . 5 8 | 1 . . | . 2 . |
 | 6 3 2 | 8 . 4 | . . . |
 |-------+-------+-------|
 | . 4 3 | . . 8 | . . . |
 | . . . | . 1 . | . . 2 |
 | . . 6 | 4 . 5 | . . . |
 |-------+-------+-------|
 | . . . | . . . | 6 . 1 |
 | . 8 . | . . . | . 3 7 |
 | 3 . . | . 8 . | 2 5 . |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
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Re: There Was a Time: 04/23/13

Postby pjb » Wed Apr 24, 2013 2:17 am

Following basics, a sequence of Sashimi X-Wings (skyscrapers if you prefer):

Sashimi X-Wing of 7s at r15c2, r16c8
7s at r6c7 and r6c8 only ones in box.
Sashimi X-Wing of 9s at r15c2, r16c8
Sashimi X-Wing of 9s at r3c59, r6c58 => stte

Phil
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Re: There Was a Time: 04/23/13

Postby Marty R. » Wed Apr 24, 2013 4:26 am

Code: Select all
+-------------+-----------------+-----------+
| 1    79 4   | 235  235   23   | 8   79 6  |
| 79   5  8   | 1    679   679  | 4   2  3  |
| 6    3  2   | 8    79    4    | 57  1  59 |
+-------------+-----------------+-----------+
| 2579 4  3   | 279  279   8    | 1   6  59 |
| 8    79 579 | 3679 1     3679 | 357 4  2  |
| 279  1  6   | 4    2379  5    | 37  79 8  |
+-------------+-----------------+-----------+
| 4579 2  579 | 3579 34579 379  | 6   8  1  |
| 45   8  15  | 256  2456  126  | 9   3  7  |
| 3    6  179 | 79   8     179  | 2   5  4  |
+-------------+-----------------+-----------+

Play this puzzle online at the Daily Sudoku site

Remote Pairs (79) plus a transport.

79r2c1-r2c56=r3c5-r3c79=r1c8-r6c8=>r6c15<>79
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Re: There Was a Time: 04/23/13

Postby ArkieTech » Wed Apr 24, 2013 11:56 am

Marty R. wrote:Remote Pairs (79) plus a transport.


Nice find! 8-)
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Re: There Was a Time: 04/23/13

Postby daj95376 » Wed Apr 24, 2013 4:51 pm

Any of several finned Franken Swordfish will crack this puzzle, but you can also use a simple X-network as well.

Code: Select all
 +-----------------------------------------------------------------------+
 |  1     a79     4      |  235    235    23     |  8      79     6      |
 | b79     5      8      |  1     c679   c679    |  4      2      3      |
 |  6      3      2      |  8     d79     4      |  57     1      59     |
 |-----------------------+-----------------------+-----------------------|
 |  2579   4      3      |  279    279    8      |  1      6      59     |
 |  8      79     579    |  3679   1      3679   |  357    4      2      |
 | e279    1      6      |  4     e2379   5      |  37    f79     8      |
 |-----------------------+-----------------------+-----------------------|
 |  4579   2      579    |  3579   34579  379    |  6      8      1      |
 |  45     8      15     |  256    2456   126    |  9      3      7      |
 |  3      6      179    |  79     8      179    |  2      5      4      |
 +-----------------------------------------------------------------------+
 # 69 eliminations remain

 (9):  r1c2 = r2c1* - r2c56 = r3c5 - *r6c15 = r6c8  =>  r1c8<>9

What I find interesting about this pattern is that it would be a simple odd-agon if r6c5 did not contain <9>. However, even with r6c5 containing <9>, it can be viewed as a Kraken odd-agon because we have:

(9): r6c5 - r23c5 = r2c6 - r2c1 = r1c2 => r1c8<>9.
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Re: There Was a Time: 04/23/13

Postby daj95376 » Wed Apr 24, 2013 5:14 pm

Marty R. wrote:
Code: Select all
+-------------+-----------------+-----------+
| 1    79 4   | 235  235   23   | 8   79 6  |
| 79   5  8   | 1    679   679  | 4   2  3  |
| 6    3  2   | 8    79    4    | 57  1  59 |
+-------------+-----------------+-----------+
| 2579 4  3   | 279  279   8    | 1   6  59 |
| 8    79 579 | 3679 1     3679 | 357 4  2  |
| 279  1  6   | 4    2379  5    | 37  79 8  |
+-------------+-----------------+-----------+
| 4579 2  579 | 3579 34579 379  | 6   8  1  |
| 45   8  15  | 256  2456  126  | 9   3  7  |
| 3    6  179 | 79   8     179  | 2   5  4  |
+-------------+-----------------+-----------+

79r2c1-r2c56=r3c5-r3c79=r1c8-r6c8=>r6c15<>79

Your notation starts with a weak inference (-), and that appears to have led you astray. If you start with a strong inference, then you'll only get r6c1<>79 -- which is insufficient to crack the puzzle.

Code: Select all
(79):  r2c1 = r2c56 - r3c5 = r3c7|r3c9 - r1c8 = r6c8  =>  r6c1<>79

Similar results -- plus an elimination in r5c7 -- can be obtained using the Skyscraper pattern a-b-c-d for the cells of the Remote Pair.

Code: Select all
 +-----------------------------------------------------------------------+
 |  1     b79     4      |  235    235    23     |  8     c79     6      |
 |  79     5      8      |  1      679    679    |  4      2      3      |
 |  6      3      2      |  8      79     4      |  57     1      59     |
 |-----------------------+-----------------------+-----------------------|
 |  2579   4      3      |  279    279    8      |  1      6      59     |
 |  8     a79     579    |  3679   1      3679   |  35-7   4      2      |
 |  2-79   1      6      |  4      2379   5      |  37    d79     8      |
 |-----------------------+-----------------------+-----------------------|
 |  4579   2      579    |  3579   34579  379    |  6      8      1      |
 |  45     8      15     |  256    2456   126    |  9      3      7      |
 |  3      6      179    |  79     8      179    |  2      5      4      |
 +-----------------------------------------------------------------------+
 # 69 eliminations remain
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Re: There Was a Time: 04/23/13

Postby Marty R. » Wed Apr 24, 2013 5:52 pm

Your notation starts with a weak inference (-), and that appears to have led you astray. If you start with a strong inference, then you'll only get r6c1<>79 -- which is insufficient to crack the puzzle.


Danny, I'm not sure exactly what you're saying, if my solution is wrong or notation is wrong or both. Based on what I think I've learned, ABCD is a valid Remote Pairs. Then I transported A to F via E.

Code: Select all
+---------------+--------------------+-------------+
|  1     79 4   | 235   235     23   | 8   C79  6  |
| F79    5  8   | 1    E679    E679  | 4    2   3  |
|  6     3  2   | 8    A79      4    | 57   1  B59 |
+---------------+--------------------+-------------+
|  2579  4  3   | 279   279     8    | 1    6   59 |
|  8     79 579 | 3679  1       3679 | 357  4   2  |
|  2-7-9 1  6   | 4     23-7-9  5    | 37  D79  8  |
+---------------+--------------------+-------------+
|  4579  2  579 | 3579  34579   379  | 6    8   1  |
|  45    8  15  | 256   2456    126  | 9    3   7  |
|  3     6  179 | 79    8       179  | 2    5   4  |
+---------------+--------------------+-------------+
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Re: There Was a Time: 04/23/13

Postby Ngisa » Wed Apr 24, 2013 6:01 pm

ArkieTech wrote:
Marty R. wrote:Remote Pairs (79) plus a transport.


Nice find! 8-)
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Re: There Was a Time: 04/23/13

Postby JC Van Hay » Wed Apr 24, 2013 6:11 pm

Marty R. wrote:Remote Pairs (79) plus a transport.

79r2c1-r2c56=r3c5-r3c79=r1c8-r6c8=>r6c15<>79
One should read instead : 79r2c1=r2c56-r3c5=r3c79-r1c8=r6c8=>r6c15<>79 :D
Another presentation : On 7s and 9s : Kite(C8R3)-r2c56=r2c1 :=> r6c51<>79
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Re: There Was a Time: 04/23/13

Postby Marty R. » Wed Apr 24, 2013 7:07 pm

JC Van Hay wrote:
Marty R. wrote:Remote Pairs (79) plus a transport.

79r2c1-r2c56=r3c5-r3c79=r1c8-r6c8=>r6c15<>79
One should read instead : 79r2c1=r2c56-r3c5=r3c79-r1c8=r6c8=>r6c15<>79 :D
Another presentation : On 7s and 9s : Kite(C8R3)-r2c56=r2c1 :=> r6c51<>79


JC, I understand your notation, but I don't understand what's wrong with my original. I know I've read that the first inference should be strong, and I accept it, but looking at my original I just can't see what about it doesn't work. The start and end cells have opposite polarity and I can't see the flaw.
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Re: There Was a Time: 04/23/13

Postby JC Van Hay » Thu Apr 25, 2013 12:40 am

Marty R. wrote:
JC Van Hay wrote:
Marty R. wrote:Remote Pairs (79) plus a transport.

79r2c1-r2c56=r3c5-r3c79=r1c8-r6c8=>r6c15<>79
One should read instead : 79r2c1=r2c56-r3c5=r3c79-r1c8=r6c8=>r6c15<>79 :D
Another presentation : On 7s and 9s : Kite(C8R3)-r2c56=r2c1 :=> r6c51<>79


JC, I understand your notation, but I don't understand what's wrong with my original. I know I've read that the first inference should be strong, and I accept it, but looking at my original I just can't see what about it doesn't work. The start and end cells have opposite polarity and I can't see the flaw.
But what does "opposite polarity" mean :roll: One true and one false :?: ...
Hope the following will make it clearer for you.
If the first and the last inferences in a chain are
  • weak, then "start" and "end" can be false, but not true together (the chain can be read : if "start" is true, then ... "end" is false -> at most one is true) :=> elimination of "start" and "end" if they are identical.
  • strong, then "start" and "end" can be true, but not false together (the chain can be read : if "start" is false, then ... "end" is true -> at least one is true) :=> elimination of any candidate seeing "start" and "end".
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Re: There Was a Time: 04/23/13

Postby daj95376 » Thu Apr 25, 2013 12:44 am

Okay Marty. Let's take one thing at a time ... starting with your Remote Pair on <79>. Cell "B" contains <59> and can't be part of a Remote Pair on <79>. Since your original chain contained r3c79, I assumed that you were transporting <7> through r3c7 and that you were transporting <9> through r3c9.

Code: Select all
 +-----------------------------------------------------------------------+
 |  1      79     4      |  235    235    23     |  8     C79     6      |
 |  79     5      8      |  1      679    679    |  4      2      3      |
 |  6      3      2      |  8     A79     4      | b57     1     B59     |
 |-----------------------+-----------------------+-----------------------|
 |  2579   4      3      |  279    279    8      |  1      6      59     |
 |  8      79     579    |  3679   1      3679   |  357    4      2      |
 |  279    1      6      |  4      2379   5      |  37    D79     8      |
 |-----------------------+-----------------------+-----------------------|
 |  4579   2      579    |  3579   34579  379    |  6      8      1      |
 |  45     8      15     |  256    2456   126    |  9      3      7      |
 |  3      6      179    |  79     8      179    |  2      5      4      |
 +-----------------------------------------------------------------------+
 # 69 eliminations remain

As for notation, your =/- usage was in error; i.e., reversed. This caused me to miss how r6c5<>79 could occur. Also, when you talk about a structure and a transport, it'd be easier on the rest of us if you wrote the structure at the start of the chain and the transport at the end (whenever possible). Example:

Code: Select all
(79):  [ r6c8 = r1c8 - r3c79 = r3c5 ] - r2c56 = r2c1  =>  r6c15<>79
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Re: There Was a Time: 04/23/13

Postby Leren » Thu Apr 25, 2013 1:45 am

Code: Select all
*--------------------------------------------------------------*
| 1    c79    4      | 235   235   23     | 8    b79    6      |
|e79    5     8      | 1    f679  f679    | 4     2     3      |
| 6     3     2      | 8    g79    4      | 57    1     59     |
|--------------------+--------------------+--------------------|
| 2579  4     3      | 279   279   8      | 1     6     59     |
| 8    d79    579    | 3679  1     3679   | 35-7  4     2      |
| 2-79  1     6      | 4     23-79 5      | 37   a79    8      |
|--------------------+--------------------+--------------------|
| 4579  2     579    | 3579  34579 379    | 6     8     1      |
| 45    8     15     | 256   2456  126    | 9     3     7      |
| 3     6     179    | 79    8     179    | 2     5     4      |
*--------------------------------------------------------------*

The way I see Marty's move is:

Code: Select all
(79): r6c8 = r1c8 - r1c2 = r5c2                => -79 r6c1, -7 r5c7
                     ||
                         = r2c1 - r2c56 = r3c5 => -79 r6c5

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Re: There Was a Time: 04/23/13

Postby Marty R. » Thu Apr 25, 2013 2:01 am

Cell "B" contains <59> and can't be part of a Remote Pair on <79>.


Danny, this is something that I learned from Keith, if I interpreted correctly. This can be Remote Pairs as long as there's a strong link: AB-AB-AC-AB.

http://www.dailysudoku.co.uk/sudoku/for ... =9089#9089

it'd be easier on the rest of us if you wrote the structure at the start of the chain and the transport at the end (whenever possible).


I don't doubt that at all, but sometimes I just can't figure out how to do it because the notation doesn't flow like my solution did. Sort of like an XY-Wing. I see the pivot and each branch but it's notated as an XY-Chain.
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Re: There Was a Time: 04/23/13

Postby daj95376 » Thu Apr 25, 2013 5:24 am

Marty R. wrote:http://www.dailysudoku.co.uk/sudoku/for ... =9089#9089

Your link is broken and I can't check your reference.
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