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Sep 1 Spring Surprise

 
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Mon Sep 01, 2008 1:01 am    Post subject: Sep 1 Spring Surprise Reply with quote

It's the first day of spring on this side of the world. The sun is warm, we're feeling good.

And, I've just solved a VH puzzle with box-line eliminations only. No wings necessary. Was the puzzle wrongly graded or did I stumble upon the solution by mistake?

Cheers
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.

PostPosted: Mon Sep 01, 2008 1:49 am    Post subject: Re: Sep 1 Spring Surprise Reply with quote

kragzy wrote:
It's the first day of spring on this side of the world. The sun is warm, we're feeling good.

And, I've just solved a VH puzzle with box-line eliminations only. No wings necessary. Was the puzzle wrongly graded or did I stumble upon the solution by mistake?

Cheers


If you want a fast answer you must show the puzzle.

Some people must wait 24 hours to see it.
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Marty R.



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

PostPosted: Mon Sep 01, 2008 3:59 am    Post subject: Reply with quote

I used one hidden UR. It's possible to solve a puzzle with basics that others need advanced solutions for. I've done it, I guess it depends in large part on the sequence in which one does things.
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nataraj



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

PostPosted: Mon Sep 01, 2008 5:54 am    Post subject: Reply with quote

Days start to feel like autumn here.

"Very hard" definitely solved by basics alone. (singles, naked pairs, not even a triple, box/line only once for that upper left box)

Time for a vacation in the sun.
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cgordon



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

PostPosted: Mon Sep 01, 2008 12:17 pm    Post subject: Reply with quote

It’s Labour Day here in Canada – the beer stores are closed and the summer is over. And that was a Medium at most. All so very sad. Crying or Very sad
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Mon Sep 01, 2008 4:00 pm    Post subject: Reply with quote

Withdrawn!

Last edited by daj95376 on Mon Sep 01, 2008 4:25 pm; edited 1 time in total
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Marty R.



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

PostPosted: Mon Sep 01, 2008 4:03 pm    Post subject: Reply with quote

Code:

+--------------+--------+-------------+
| 1359 13  38  | 2 6  7 | 389 4  3589 |
| 45   24  248 | 1 9  3 | 68  56 7    |
| 379  6   37  | 5 8  4 | 1   2  39   |
+--------------+--------+-------------+
| 8    235 235 | 4 23 1 | 7   9  6    |
| 14   124 9   | 6 7  8 | 5   3  24   |
| 34   7   6   | 9 23 5 | 24  8  1    |
+--------------+--------+-------------+
| 36   8   1   | 7 4  9 | 236 56 235  |
| 2    45  45  | 3 1  6 | 89  7  89   |
| 367  9   37  | 8 5  2 | 346 1  34   |
+--------------+--------+-------------+

Play this puzzle online at the Daily Sudoku site

Just as a point of potential interest. This is where I am after basics. As noted above, I solved the puzzle with the hidden UR on 89 in boxes 39.

However, there is a potential DP on 24-25-45 in boxes 147. R2c3 must be = 8 or r4c2or r4c3 must be = 3 to kill the DP. Either way, r4c5 must be = 2 and that also solves the puzzle.
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A.J.



Joined: 21 Mar 2008
Posts: 5
Location: San Diego, CA

PostPosted: Mon Sep 01, 2008 4:42 pm    Post subject: Reply with quote

Code:

+--------------+--------+-------------+
| 1359 13 38 | 2 6 7 | 389 4 3589 |
| 45 24 248 | 1 9 3 | 68 56 7 |
| 379 6 37 | 5 8 4 | 1 2 39 |
+--------------+--------+-------------+
| 8 235 235 | 4 23 1 | 7 9 6 |
| 14 124 9 | 6 7 8 | 5 3 24 |
| 34 7 6 | 9 23 5 | 24 8 1 |
+--------------+--------+-------------+
| 36 8 1 | 7 4 9 | 236 56 235 |
| 2 45 45 | 3 1 6 | 89 7 89 |
| 367 9 37 | 8 5 2 | 346 1 34 |
+--------------+--------+-------------+

The naked pair 37 in column 3 eliminates the 3 in R1, C3 and it falls apart from their. No advanced techniques required. Very Happy
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Mon Sep 01, 2008 4:44 pm    Post subject: Reply with quote

Marty R. wrote:
Code:

+--------------+--------+-------------+
| 1359 13  38  | 2 6  7 | 389 4  3589 |
| 45   24  248 | 1 9  3 | 68  56 7    |
| 379  6   37  | 5 8  4 | 1   2  39   |
+--------------+--------+-------------+
| 8    235 235 | 4 23 1 | 7   9  6    |
| 14   124 9   | 6 7  8 | 5   3  24   |
| 34   7   6   | 9 23 5 | 24  8  1    |
+--------------+--------+-------------+
| 36   8   1   | 7 4  9 | 236 56 235  |
| 2    45  45  | 3 1  6 | 89  7  89   |
| 367  9   37  | 8 5  2 | 346 1  34   |
+--------------+--------+-------------+


However, there is a potential DP on 24-25-45 in boxes 147. R2c3 must be = 8 or r4c2or r4c3 must be = 3 to kill the DP. Either way, r4c5 must be = 2 and that also solves the puzzle.


Marty, I never found the chain that forces r4c5=2 when r2c3=8, but noticed that the <37> pair in r39c3 forces the <8> deletion from r2c3 thereby making r4c5=2 to prevent the DP.

Ted
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Marty R.



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

PostPosted: Mon Sep 01, 2008 5:51 pm    Post subject: Reply with quote

Quote:
Marty, I never found the chain that forces r4c5=2 when r2c3=8, but noticed that the <37> pair in r39c3 forces the <8> deletion from r2c3 thereby making r4c5=2 to prevent the DP.


Ted, if I did this thing correctly, the chain runs alphabetically from <a> to <h>. After <h> is solved for <2>, the <35> pair is exposed in that box, forcing r4c5 = <2>.

I did not use this DP in my solution, I just posted it for the benefit of anyone who might not be familiar with this type of DP.

Code:
+--------------+--------+-------------------+
| 1359  13   38   | 2 6  7 | 389  4    3589 |
| 45    24   248a | 1 9  3 | 68b  56c  7    |
| 379   6    37   | 5 8  4 | 1    2    39   |
+--------------+--------+-------------------+
| 8     235  235  | 4 23 1 | 7    9    6    |
| 14g   124h 9    | 6 7  8 | 5    3    24   |
| 34f   7    6    | 9 23 5 | 24   8    1    |
+--------------+--------+-------------------+
| 36e   8    1    | 7 4  9 | 236  56d  235  |
| 2     45   45   | 3 1  6 | 89   7    89   |
| 367   9    37   | 8 5  2 | 346  1    34   |
+--------------+--------+-------------------+
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cgordon



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

PostPosted: Mon Sep 01, 2008 8:50 pm    Post subject: Reply with quote

Marty: Maybe I'm missing something here but why not follow the trail from b=8 and not 6. Why not go to the <13> at R1C2 and follow the chains for <3> (which soon leads to oblivion). I am not convinced this is anything more than Trial and Error - which should not be sanctioned by sophisticates - like what we is.

Cheers
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Marty R.



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

PostPosted: Mon Sep 01, 2008 9:11 pm    Post subject: Reply with quote

cgordon wrote:
Marty: Maybe I'm missing something here but why not follow the trail from b=8 and not 6. Why not go to the <13> at R1C2 and follow the chains for <3> (which soon leads to oblivion). I am not convinced this is anything more than Trial and Error - which should not be sanctioned by sophisticates - like what we is.

Cheers

Craig,

About all you're missing here is that I is not no sophisticate, whatever dat means. Question Question

I agree that it has an element of trial-and-error. However, a number of people here accept the fact that a forcing chain (which I believe this to be) has some legitimacy when recognition of a pattern leads to it, as opposed to the examples you mention, which are just random.

The same principle seems to apply to other situations, such as BUG+2 or 3, a Type 3 UR, a so-called Finned XY-Wing and others. I'm not 100% comfortable with these things, but they do seem to have a little more cachet than random chains.
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cgordon



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

PostPosted: Mon Sep 01, 2008 9:41 pm    Post subject: Reply with quote

Marty: I can see how a pattern could lead to a logical reduction or chain - but it's this bit I don't understand
Quote:
However, there is a potential DP on 24-25-45 in boxes 147.
To my limited understanding a DP is associated with a UR and a rectangular pattern. I just don't see that here?

Craig
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Wendy W



Joined: 04 Feb 2008
Posts: 144

PostPosted: Mon Sep 01, 2008 11:02 pm    Post subject: Reply with quote

Just adding my 2 cents here -- I agree with everybody that this was an EZ one today, not even an xy wing required. But I find that reassuring, given that I have just reached a significant birthday milestone.
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Marty R.



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

PostPosted: Tue Sep 02, 2008 12:24 am    Post subject: Reply with quote

cgordon wrote:
Marty: I can see how a pattern could lead to a logical reduction or chain - but it's this bit I don't understand
Quote:
However, there is a potential DP on 24-25-45 in boxes 147.
To my limited understanding a DP is associated with a UR and a rectangular pattern. I just don't see that here?

Craig

Not necessarily. The BUG+1 (or 2 or 3) involves a DP as well. In this case, if the six cells were 24-24-25-25-45-45 there would be interchangeability, thus resulting in non-unique solutions.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Sep 02, 2008 4:29 am    Post subject: Reply with quote

Happy x0th birthday Wendy.
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cgordon



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

PostPosted: Tue Sep 02, 2008 7:20 pm    Post subject: Reply with quote

Quote:
Not necessarily. The BUG+1 (or 2 or 3) involves a DP as well. In this case, if the six cells were 24-24-25-25-45-45 there would be interchangeability, thus resulting in non-unique solutions.


There's only one thing I understood in the the last ten posts. Happy Birthday Wendy !
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Sep 04, 2008 6:55 am    Post subject: Reply with quote

Wendy W wrote:
Just adding my 2 cents here -- I agree with everybody that this was an EZ one today, not even an xy wing required. But I find that reassuring, given that I have just reached a significant birthday milestone.


I am guessing 40

my second guess is 50
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