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What's the logic behind remote naked pairs

 
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kowloon



Joined: 28 Sep 2006
Posts: 3
PostPosted: Thu Oct 05, 2006 12:06 pm    Post subject: What's the logic behind remote naked pairs Reply with quote
I thought I understood it once but now I can't figure it out. What is the logic behind remote naked pairs?
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado
PostPosted: Thu Oct 05, 2006 3:02 pm    Post subject: It depends ... Reply with quote
Hi, Kowloon!

I'm not certain I understand your question, but maybe this is what you're asking about.
Code:
  46+   .     .     .     .     .     *     .     .
  .     .     .     .     .     .     .     .     .
  .     .     46-   .     .     .     .     .     *
  .     .     .     .     .     .     .     .     .
  .     .     .     .     .     .     .     .     .
  .     .     .     .     .     .     .     .     .
  .     .     .     .     .     .     .     .     46+
  .     .     46+   .     .     .     46-   .     .
  .     46-   .     .     .     .     .     .     .

In this made-up example, the linked pairs {4, 6} form a chain through the puzzle -- we call these "remote pairs". In this example we can reason as follows.

r1c1 = 4 ==> r3c3 = 6 ==> r8c3 = 4 ==> r8c7 = 6 ==> r7c9 = 4
r1c1 = 6 ==> r3c3 = 4 ==> r8c3 = 6 ==> r8c7 = 4 ==> r7c9 = 6

So there's either a "4" at r1c1, and a "6" at r8c7, or else there's a "6" at r1c1, and a "4" at r8c7. Either way there cannot possibly be either a "4" or a "6" at r1c7. We can use similar reasoning to eliminate the possibility of either "4" or "6" at r3c9.

I hope that answers your question. dcb
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kowloon



Joined: 28 Sep 2006
Posts: 3
PostPosted: Sat Oct 07, 2006 3:27 am    Post subject: Reply with quote
I see now. I thought it was something different which is why it didn't make sense. Thanks for the explanation.
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