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Bit of more than I can chew...need some help!!

 
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daykart



Joined: 22 Nov 2005
Posts: 10

PostPosted: Wed Jan 04, 2006 11:26 pm    Post subject: Bit of more than I can chew...need some help!! Reply with quote

After getting assistance with some of my earlier posts, many of you have helped me get through the last 4 very hard puzzles all by myself.
Therefore, I decided to try something harder.
The folowing puzzle comes off of a NY Times Su Doku site.

I am not interested in the answer...but there are some big holes in my logic, and I need aid with that. I have looked for "hidden pairs", single number is a row or column, and everything else that I know of. If I did not make a silly omission, then there is a lot more to Su Doku than I am aware of.

Enlighten me, please.


_ _ _ _ _ _ _ 1 8
_ _ 8 4 9 1 _ 2 _
_ _ 1 _ 3 8 _ _ _

_ 4 _ _ _ _ 8 _ 2
6 3 _ _ _ _ 7 4 1
8 _ 7 _ _ 4 _ 9 _

_ _ _ 6 4 _ 5 _ _
_ 9 _ _ 2 _ 1 _ _
_ _ _ _ _ 3 2 _ _

r1c1 2,3,4,5,7,9 c2 2,5,7,9 c3 2,3,4,5,9 c4 2,5,7 c5 1,5,6 c6 2,5,6,7
c7 4,9

r2c1 3,5,7 c2 5,6,7 c6 3,6 c8 3,5,6,7

r3c1 2,4,5,7,9 c2 2,5,6,7 c4 2,5,7 c7 4,9 c8 5,6,7 c9 5,6,7

r4c1 1,5,9 c5 5,9 c4 1,3,5,7,9 c5 1,5,6,7 c6 5,6,7,9 c8 3,5,6

r5c3 2,5,9 c4 2,5,8,9 c5 5,8 c6 2,5,9

r6c2 1,2,5 c4 1,2,3,5 c5 1,5,6 c7 3,6 c9 3,5,6

r7c1 1,2,3,7 c2 1,2,7,8 c3 2,3 c6 7,9 c8 3,7,8 c9 3,7,9

r8c1 3,4,5,7 c3 3,4,5,6 c4 5,7,8 c6 5,7 c8 3,6,7,8 c9 3,4,6,7

r9c1 4,5,7 c2 5,6,7,8 c3 4,5,6 c4 1,5,7,8,9 c5 1,5,7,8 c8 6,7,8
c9 4,6,7,9

Thanks for any explanations you can offer.
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Thu Jan 05, 2006 1:10 am    Post subject: Look for naked quads Reply with quote

This one's not really so bad, Daykart. At least, it's fairly easy to get started.

1. There's a pair {3, 6} in column 6, r2 & r6.
2. Eliminating 3 & 6 in col 6 reveals {4, 9} pair in col 6, r1 & r3.
3. Eliminating 4 & 9 in top right 3x3 box (at r3c9) reveals naked quad {2, 5, 6, 7} in row 3, and also second piece of hidden pair {4, 9} -- pair at r1c3 & r6c3.
4. The same naked quad {2, 5, 6, 7} appears in row 1. Elimination reveals triplet {3, 4, 9} in r1c1, r1c3, & r1c6.

5. Now we have a value -- r7c1 = 2 (unique in column)
6. r7c3 = 3 (sole candidate)
7. Pair {7, 9} revealed in row 7, at r7c6 & r7c9. This leads to
8. r7c8 = 8
9. r7c2 = 1

and you can make good progress from there. dcb
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Thu Jan 05, 2006 1:31 am    Post subject: Did you copy this puzzle correctly? Reply with quote

Hi, Daykart! It's me again.

After I posted the brief explanation of how to place the first few digits in this puzzle, I continued working on it, and arrived at a contradiction (two occurences of "6" in row 9, the way I went at it). So I tried again, with the same result.

So then I got suspicious and fed the puzzle to an automated solver, which informed me that there are no valid solutions to the puzzle you posted.

Either you transcribed it incorrectly, or it was a bum puzzle to start with! dcb
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