There Was a Time: 04/23/13

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

Postby JasonLion » Thu Apr 25, 2013 1:34 pm

I believe the link is http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?p=9089#9089.

Links need to be enclosed in a URL command, like this:
Code: Select all
[url]http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?p=9089#9089[/url]
or they tend to get broken by the forum software.
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Re: There Was a Time: 04/23/13

Postby daj95376 » Thu Apr 25, 2013 4:35 pm

JasonLion: Thanks for the completed link.

Marty: I'd forgotten about Keith's General Remote Pair discussion. All of his logic in that thread is based on chains using strong links where weak inferences occur.

For my puzzle, I see his logic working as Double Implication Chains using the same cells for each DIC path:

Code: Select all
(  9)r3c5 - r3c9 = r1c8 - (9=7)r6c8   -->>   if r3c5=9 then r6c8=7 and r6c5<>79
(7-9)r3c5 = r3c9 - r1c8 = (9  )r6c8   -->>   if r3c5=7 then r6c8=9 and r6c5<>79

Code: Select all
(  9)r2c1 - r2c56 = r3c5 - r3c9 = r1c8 - (9=7)r6c8   -->>   if r2c1=9 then r6c8=7 and r6c1<>79
(7-9)r2c1 = r2c56 - r3c5 = r3c9 - r1c8 = (9  )r6c8   -->>   if r2c1=7 then r6c8=9 and r6c1<>79

No matter which value you assume as true in the starting cell, the strong links on <9> forces the strong/weak inferences to alternate ... and the ending cell is forced to contain the alternate value.
Last edited by daj95376 on Thu Apr 25, 2013 5:15 pm, edited 1 time in total.
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Re: There Was a Time: 04/23/13

Postby Marty R. » Thu Apr 25, 2013 4:45 pm

daj95376 wrote:JasonLion: Thanks for the completed link.

Marty: I'd forgotten about Keith's General Remote Pair discussion.


Is it correct then, in summary, to say the solution was valid but my notation was poor?

Thanks Danny, JC and Leren for your help and suggestions. The learning process is never-ending.
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Re: There Was a Time: 04/23/13

Postby daj95376 » Thu Apr 25, 2013 5:30 pm

Marty R. wrote:Is it correct then, in summary, to say the solution was valid but my notation was poor?

Marty,

I altered my post above because it was inaccurate. It now contains the DIC notation that I would have used. I'm not sure that you need to go to this extreme for the notation of your solution, but it would have helped (me) if you had mentioned that you were using Keith's General Remote Pair logic.
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Re: There Was a Time: 04/23/13

Postby Marty R. » Thu Apr 25, 2013 5:57 pm

but it would have helped (me) if you had mentioned that you were using Keith's General Remote Pair logic.


Sorry for the inconvenience, I made some false assumptions.
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Re: There Was a Time: 04/23/13

Postby Leren » Thu Apr 25, 2013 9:59 pm

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      | 79-2  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    |h79    8     179    | 2     5     4      |
*--------------------------------------------------------------*

I can see a 6th direct elimination from the remote pair (79) logic.

r3c5 & r5c2 (cells marked d & g) have the same parity (polarity/colour) ie r3c5, r5c2 = 7 or r3c5, r5c2 = 9

if r3c5, r5c2 = 7 => r4c4 = 7; if r3c5, r5c2 = 9 => r4c4 = 9; => r4c4 = 79 ie r4c4 <> 2

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