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August 5th - stuck!

 
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KSipher



Joined: 24 Sep 2006
Posts: 38

PostPosted: Tue Oct 17, 2006 2:04 am    Post subject: August 5th - stuck! Reply with quote

I'm stuck at the following point. Grrrr. Can anyone lead me to the next step. Thanks -
Kathy

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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Oct 17, 2006 5:25 am    Post subject: Reply with quote

Here's a few moves I see in the short amount of time I have (past my bedtime).

In box 6 there is a naked pair 38 which will eliminate a few candidates.

That means locked candidates must eliminate 3s from c8 and c9 in box 3, which solves r1c9 for 5.

Because of locked candidates, the 3s get eliminated from c1 in box 1 and the 4s get eliminated from c1 in box 7.

Hope this helps.
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KSipher



Joined: 24 Sep 2006
Posts: 38

PostPosted: Tue Oct 17, 2006 4:15 pm    Post subject: more help? Reply with quote

Hi -
Thanks for your quick reply, I feel foolish that I didn't see the naked pair in box 6. But I feel even more foolish that I don't see the locked candidates that eliminate the 3s from column 8 & 9 in box 3. Can you explain this a little more?

Gosh, I feel like such a neebie... javascript:emoticon('Confused')

Thanks so much
Kathy
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Oct 17, 2006 4:53 pm    Post subject: Reply with quote

Quote:

Thanks for your quick reply, I feel foolish that I didn't see the naked pair in box 6. But I feel even more foolish that I don't see the locked candidates that eliminate the 3s from column 8 & 9 in box 3. Can you explain this a little more?


I assume you're looking for a definition of locked candidates, also known as box-line or box-box interactions. There are two forms:

1) If the possibilities for a number in a row or column are confined (locked) to one box, then that number must be eliminated from other rows/columns in that box.

2) If the possibilities for a number in a box are confined to one row or column, then that number must be eliminated from that part of the row/column outside of the box.

I can't think of a puzzle I've done that hasn't used this technique.

This will explain it better and show some illustrations. Just scroll down to "Beyond the basics:"

http://www.angusj.com/sudoku/hints.php

Good luck. Don't hesitate to ask questions. This forum has taught me a lot and it can do the same for anyone else.
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KSipher



Joined: 24 Sep 2006
Posts: 38

PostPosted: Tue Oct 17, 2006 6:22 pm    Post subject: August 5th - stuck! Reply with quote

Marty

Thanks for your help. I do understand locked candidates, but I just wasn't seeing it. I'm still learning to recognize and apply the techniques I read about here (and elsewhere) and appreciate, so much, the help I can get here. After eliminating the 3 in row1 col9, the rest of the puzzle was easy. Thanks again.

Kathy[/quote]
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Oct 17, 2006 9:30 pm    Post subject: Reply with quote

Quote:
I do understand locked candidates, but I just wasn't seeing it. I'm still learning to recognize and apply the techniques I read about here


For me, recognizing locked candidates depends on a systematic search. I do all my puzzles with pencil and paper. After an initial scan of bands and stacks, I write candidates in all unsolved cells. Then I carefully scan each row, column and box, looking for pairs, triples, quads, etc. and locked candidates.

I'll still miss some, but I wouldn't spot most of the ones I do if I wasn't systematically searching for them.
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