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Jul 18 VH

 
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hughwill



Joined: 05 Apr 2010
Posts: 424
Location: Birmingham UK
PostPosted: Sat Jul 18, 2015 11:14 am    Post subject: Jul 18 VH Reply with quote
After basics:
Code:

+---------------+---------------+---------------+
| 157  8   9    | 1257 6   125  | 125  4    3   |
| 1457 17  1457 | 3    579 1258 | 1259 1256 689 |
| 6    2   3    | 158  459 1458 | 7    15   89  |
+---------------+---------------+---------------+
| 147  167 1467 | 5678 57  9    | 48   3    2   |
| 9    3   2467 | 2678 1   268  | 48   67   5   |
| 8    5   267  | 4    3   26   | 19   167  69  |
+---------------+---------------+---------------+
| 2    16  8    | 156  45  1456 | 3    9    7   |
| 3    9   16   | 16   8   7    | 25   25   4   |
| 57   4   57   | 9    2   3    | 6    8    1   |
+---------------+---------------+---------------+

Play this puzzle online at the Daily Sudoku site

A right cracker today- really hard (for me) to see.....(select to view)
Quote:
X-Wing on 7 c25 - then a hidden pair in c4 finally revealing
a 276 XY-Wing pivot r5c4 which sets r6c9 to 9 and sorts it.
Best VH for ages.
Hugh
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bat999



Joined: 09 Jul 2015
Posts: 55
Location: UK
PostPosted: Sat Jul 18, 2015 12:42 pm    Post subject: Reply with quote
Yes, nice puzzle today. Very Happy
Code:
.--------------------.------------------.-----------------.
| c157    8     9    | d1257  6    125  | 125   4     3   |
|  1457  b17    1457 |  3     579  1258 | 1259  1256  689 |
|  6      2     3    |  158   459  1458 | 7     15    89  |
:--------------------+------------------+-----------------:
|  147   a167   1467 |  5678  57   9    | 48    3     2   |
|  9      3    f2467 | e2678  1    268  | 48    67    5   |
|  8      5    g26-7 |  4     3    26   | 19    167   69  |
:--------------------+------------------+-----------------:
|  2      16    8    |  156   45   1456 | 3     9     7   |
|  3      9     16   |  16    8    7    | 25    25    4   |
|  57     4     57   |  9     2    3    | 6     8     1   |
'--------------------'------------------'-----------------'
(7)r4c2 = r2c2 - r1c1 = (7-2)r1c4 = r5c4 - r5c3 = (2)r6c3 => -7 r6c3; stte
Cool

Last edited by bat999 on Thu Jul 23, 2015 5:56 pm; edited 4 times in total
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lg161



Joined: 17 Oct 2006
Posts: 12
PostPosted: Sat Jul 18, 2015 6:54 pm    Post subject: July 18 vh Reply with quote
I see the two entries for this but not the solution!
I used the online hint function. Got to 9 in r6 c9 with no explanation.
Help!
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dongrave



Joined: 06 Mar 2014
Posts: 568
PostPosted: Sat Jul 18, 2015 7:40 pm    Post subject: Reply with quote
Thanks Hugh for listing the solution using just standard VH moves! I completely missed it!

Hey lg161, take the grid that Hugh posted and apply the 7 x-wing that he mentioned in c25 which removes the 7's from r2c13 and r4c134. Then the hidden 27 in c4 removes the 1&5 from r1c4 and removes the 6&8 from r5c4. Then the 27-6 xy-wing with pivot at r5c4 removes the 6 from r5c6 and from r6c89 so r6c9 is 9! After that, you get a handful of simple ones BUT then you still have to watch out for some lone 8's and 9's to solve it. No wonder I missed it. What a great puzzle!
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lg161



Joined: 17 Oct 2006
Posts: 12
PostPosted: Sat Jul 18, 2015 8:30 pm    Post subject: Dongrave solution Reply with quote
Thank you so much! Got the 7s but not the hidden 27s.
Wish I had your eyes (and brain)!
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dongrave



Joined: 06 Mar 2014
Posts: 568
PostPosted: Sun Jul 19, 2015 12:58 am    Post subject: Re: Dongrave solution Reply with quote
lg161 wrote:
Thank you so much! Got the 7s but not the hidden 27s.
Wish I had your eyes (and brain)!


I sure hope you're referring to Hugh's brain and not mine lg! I completely missed it until Hugh lead me to the solution like a blind pig to the corn. ugh.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sun Jul 19, 2015 3:02 am    Post subject: Reply with quote
dongrave wrote:
Thanks Hugh for listing the solution using just standard VH moves! I completely missed it!

Hey lg161, take the grid that Hugh posted and apply the 7 x-wing that he mentioned in c25 which removes the 7's from r2c13 and r4c134. Then the hidden 27 in c4 removes the 1&5 from r1c4 and removes the 6&8 from r5c4. Then the 27-6 xy-wing with pivot at r5c4 removes the 6 from r5c6 and from r6c89 so r6c9 is 9! After that, you get a handful of simple ones BUT then you still have to watch out for some lone 8's and 9's to solve it. No wonder I missed it. What a great puzzle!


Don, I want to take the liberty of rewording part of your post.

"Then the hidden 27 in c4 removes the 1&5 from r1c4 and removes the 6&8 from r5c4."

Then the 1568 quad in c4 removes the 1&5 from r1c4 and removes the 6&8 from r5c4.

I'm not writing about anything that's right or wrong, I'm writing only about my personal preferences. I don't deal with hidden pairs (or triples or whatever) very well. All hidden pairs have complementary naked subsets. I can (sometimes) spot naked subsets, but rarely (if ever) hidden sets. So when I see a hidden something referenced I immediately look for the naked subset that I know is there. To repeat what I said above, this is nothing more than a personal preference.
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dongrave



Joined: 06 Mar 2014
Posts: 568
PostPosted: Sun Jul 19, 2015 4:35 pm    Post subject: Reply with quote
Hi Marty! It's just like deva vu all over again! You and I discussed this same thing a year ago! (Check out the 'JUL 31 VH' thread from 2014.) I was surprised to hear back then that you found it easier to find any type of quads than pairs! And you also mentioned the complementary subsets of hidden sets (which obviously didn't stick with me). Maybe it's just me - I seem to find hidden pairs a lot easier than naked quads! Weird! Thanks, Don.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sun Jul 19, 2015 6:15 pm    Post subject: Reply with quote
You've got a good memory to know that I'd said that previously. I'm getting senile, repeating myself. If you can find hidden pairs, then more power to you. I doubt if I could find them. But when I do a puzzle I'm looking for subsets. That's my mindset. I don't even think about hiddens, they're not in my arsenal.
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barbsart



Joined: 20 Jul 2015
Posts: 1
Location: Boston, MA, USA
PostPosted: Mon Jul 20, 2015 2:03 pm    Post subject: hardest puzzle yet Reply with quote
Thank you Hugh !
"got the 7's but not the 27s"
Amazing. The longer I looked at this puzzle the less I could see it.
Couldn't believe dailysudoku.com would put up a puzzle not analytically possible. In over 5 years - this was the hardest yet.

THANK YOU. Now I can get back to work.
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