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Friday 7 July - Hard or VERY HARD???

 
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tsfreaks



Joined: 07 Jul 2006
Posts: 2

PostPosted: Fri Jul 07, 2006 7:26 am    Post subject: Friday 7 July - Hard or VERY HARD??? Reply with quote

I'm stuck. HELP!!!

I've tried X-Wing, XY-Wing, XYZ-Wing with no luck. I don't wanna have to resort to Forcing chains/guesswork. How is it that this is only hard??

What technique am I missing??

So far I have:

Code:

 *-----------------------*
 | - - - | 8 - 1 | - 5 3 |
 | - 3 - | - - - | - - 9 |
 | 8 2 - | 3 5 7 | 6 - - |
 |-------+-------+-------|
 | 3 1 8 | - - - | 9 - - |
 | 2 - - | 9 - 8 | - - - |
 | - - 6 | - - - | 8 2 5 |
 |-------+-------+-------|
 | - 8 2 | 6 4 - | - 7 - |
 | 7 - - | - - - | - 8 6 |
 | 1 6 - | 7 8 - | - - 2 |
 *-----------------------*




Thanks!
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Fri Jul 07, 2006 10:49 am    Post subject: Reply with quote

Your puzzle appears to have an error in r2c9, as it is given in the initial clue set as 8.
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TexCat



Joined: 07 Jul 2006
Posts: 31

PostPosted: Fri Jul 07, 2006 2:42 pm    Post subject: Reply with quote

I was stuck at the same place forever, but finally got unstuck just by looking at column 5.
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David Bryant



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

PostPosted: Fri Jul 07, 2006 5:31 pm    Post subject: You need some hidden pairs Reply with quote

Code:
 *-----------------------*
 | - - - | 8 - 1 | - 5 3 |
 | - 3 - | - - - | - - 8 |
 | 8 2 - | 3 5 7 | 6 - - |
 |-------+-------+-------|
 | 3 1 8 | - - - | 9 - - |
 | 2 - - | 9 - 8 | - - - |
 | - - 6 | - - - | 8 2 5 |
 |-------+-------+-------|
 | - 8 2 | 6 4 - | - 7 - |
 | 7 - - | - - - | - 8 6 |
 | 1 6 - | 7 8 - | - - 2 |
 *-----------------------*

All that's needed to make some progress are a couple of hidden pairs.

-- Because of the {2, 7} appearing in row 3 and in column 8, there must be a hidden pair {2, 7} in the top right 3x3 box, in r1c7 & r2c7.

-- The other hidden pair is harder to spot. First, notice the "1" at r1c6 and the "3"s at r1c9 and r2c2. Clearly neither "1" nor "3" can appear at r1c5 or r2c5. {1, 3} can't fit in at r4c5 either, because of the {1, 3} in r4c1&2. Finally, because of a row on block interaction we can infer that the {1, 3} in row 5 must fall in the middle right 3x3 box (that is, in r5c7-9) because row 6 is already filled in that box. So there can't be a "1" or a "3" in r5c5. We can conclude, then, that the pair {1, 3} must occupy r6c5 & r8c5.

With this step completed you should be able to find the triplet {1, 3, 4} in r6c4-6, leaving only the pair {7, 9} to occupy r6c1&2 ... the rest should be fairly simple. dcb
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tsfreaks



Joined: 07 Jul 2006
Posts: 2

PostPosted: Sun Jul 09, 2006 11:32 pm    Post subject: Reply with quote

Thanks. I'm an idiot.
Must've been Friday-itis. Can't figure out why I missed that 1,3 pair.
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stanford1983



Joined: 16 Jul 2006
Posts: 1
Location: Euless, Texas

PostPosted: Sun Jul 16, 2006 2:55 am    Post subject: But wait Reply with quote

I found the 1,3 pairing in row 6 but could not determine if 4 or 7 was the third partner. It turns out to be a 4, but without knowing that, a 7 in r6c2 is not the logical choice as the next hint suggests.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jul 16, 2006 12:13 pm    Post subject: Reply with quote

The (1,3) hidden pair is in column 5 (or if you prefer, the [2,6,7,9] naked quad), which then excludes 7 from r6c5 and leaves r6c2 as the only 7 in row 6.
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