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Oct 15 "very hard" Hard - Try It!

 
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Tue Oct 16, 2007 12:21 am    Post subject: Oct 15 "very hard" Hard - Try It! Reply with quote

Sometimes the VHs are "very easy" but are classified as VHs because they contain an "advanced step" - which may be nothing more challenging than an easy to spot X wing. I tried today's Hard puzzle, just for the helluvit, and found it very challenging (actually I'm still working on it). Try it for a change - without any "advanced steps".
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Tue Oct 16, 2007 1:21 am    Post subject: Reply with quote

I agree. The "key" step is something very basic (hence "Hard" rather than "Very Hard") but not so easy to spot.
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Captain Pete



Joined: 09 Jun 2007
Posts: 55
Location: Oley, PA

PostPosted: Tue Oct 16, 2007 1:33 am    Post subject: Reply with quote

I give up... what is the key I'm missing?
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Marty R.



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

PostPosted: Tue Oct 16, 2007 4:58 am    Post subject: Reply with quote

Captain Pete wrote:
I give up... what is the key I'm missing?

I don't recall one "key" step, but you should solve it if you look very carefully for triples, quads and locked candidates.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Tue Oct 16, 2007 6:25 am    Post subject: Reply with quote

don't know if there was one single "key" step.
The ones that took me longest to spot were

SPOILER ALERT

- the "4" confined to col 1 in box 7, also "4" confined to box 1 in col 2
- the 12789 vs. hidden pair 35 in col 9

END SPOILER ALERT

all in all, a rather tough "hard"
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duffy



Joined: 13 Sep 2007
Posts: 26
Location: Toronto Canada

PostPosted: Tue Oct 16, 2007 1:02 pm    Post subject: Reply with quote

Now that the "spoiler" is out there, I have to say that the positioning of the pair in c9 among an especially large number of alternative candidates was truly difficult for me to spot. (I found it after resorting to a stategic "trial and error" approach.) Since the pair stradles a box boundary, I found it at first surprising to note the effect it had on the available 9's in r6, after which the solution was straightforward. I think it was surprising because this kind of interaction has been uncommon in my obsessive (according to my family) experience.
Rolling Eyes
Don D.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Tue Oct 16, 2007 2:29 pm    Post subject: COL 9 WAS MY BREAKTHROUGH Reply with quote

Each to his own problem. I agree it was tough for "Hard" but I often find this to be so, it taking longer over some "hard" than some "V Hard".

For me the breakthrough that took some time to spot was recognising the "attack of 35s" on column 9 - thereafter it wasn't too time consuming!
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sweedy



Joined: 21 Oct 2005
Posts: 3
Location: Zurich

PostPosted: Tue Oct 16, 2007 4:08 pm    Post subject: I really must be stupid Reply with quote

I really gave up on that one yesterday after not seeing the solution after a while.. I did spot the hidden 35 pair in c9 but still I don't see how this helps!
I don't see how the "4" confined to col 1 in box 7, or how the "4" is confined to box 1 in col 2..
what effect does this 35-pair have on the 9s in r6?? help!!!
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duffy



Joined: 13 Sep 2007
Posts: 26
Location: Toronto Canada

PostPosted: Tue Oct 16, 2007 5:08 pm    Post subject: Reply with quote

Sweedy,
Consider the point at which I got stuck:
Code:

+-----------------+---------+-----------------+
| 1    24579 258  | 6 49 3  | 4789 24789 2789 |
| 278  24679 268  | 1 49 27 | 5    3     2789 |
| 237  49    23   | 8 5  27 | 6    49    19   |
+-----------------+---------+-----------------+
| 9    8     4    | 3 6  5  | 2    17    17   |
| 6    125   1235 | 7 18 9  | 38   58    4    |
| 35   15    7    | 2 18 4  | 389  6     3589 |
+-----------------+---------+-----------------+
| 245  16    16   | 9 7  8  | 34   245   235  |
| 478  3     9    | 5 2  6  | 1    478   78   |
| 2578 257   258  | 4 3  1  | 789  25789 6    |
+-----------------+---------+-----------------+

(The naked triple 237 in r3 helped to get this far.)
After rubbing out the extras in the 35 pair in c9, you can see that the 35 in r6c9 leaves only one 9 in r6. This leads to advances in box9 and c7....
Idea
Don D.
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duffy



Joined: 13 Sep 2007
Posts: 26
Location: Toronto Canada

PostPosted: Tue Oct 16, 2007 5:13 pm    Post subject: Reply with quote

In a rush, I often do something wrong: There should have been a 1 in r3c8 as follows:
Code:
+-----------------+---------+-----------------+
| 1    24579 258  | 6 49 3  | 4789 24789 2789 |
| 278  24679 268  | 1 49 27 | 5    3     2789 |
| 237  49    23   | 8 5  27 | 6    149   19   |
+-----------------+---------+-----------------+
| 9    8     4    | 3 6  5  | 2    17    17   |
| 6    125   1235 | 7 18 9  | 38   58    4    |
| 35   15    7    | 2 18 4  | 389  6     3589 |
+-----------------+---------+-----------------+
| 245  16    16   | 9 7  8  | 34   245   235  |
| 478  3     9    | 5 2  6  | 1    478   78   |
| 2578 257   258  | 4 3  1  | 789  25789 6    |
+-----------------+---------+-----------------+

Embarassed
Don D.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Tue Oct 16, 2007 7:24 pm    Post subject: Reply with quote

Quote:
- the 12789 vs. hidden pair 35 in col 9


Aye: there's the rub. I gave up until seeing Nataraj's post. Interesting though - isn't the 12789 a NAKED QUINTUPLET?
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Marty R.



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

PostPosted: Tue Oct 16, 2007 9:12 pm    Post subject: Reply with quote

cgordon wrote:
Quote:
- the 12789 vs. hidden pair 35 in col 9


Aye: there's the rub. I gave up until seeing Nataraj's post. Interesting though - isn't the 12789 a NAKED QUINTUPLET?


Yes it is. A number of people talk about hidden pairs or triples, but the way my mind works, I always look for the complementary subsets, not the hidden stuff (except hidden singles).
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Tue Oct 16, 2007 9:38 pm    Post subject: Reply with quote

Yes... my "key" was the hidden {35} pair.


Sweedy,

I don't believe your question about the <4>s was answered. Once the <6> and <1> are solved in C6 of Box 8, the {16} locked pair occurs in R7C23 of Box 7. The only place left for <4> in Box 7 is then R78C1.
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