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Aug 18 VH

 
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RobertRattley



Joined: 24 Jun 2007
Posts: 57
Location: Australia

PostPosted: Sun Aug 17, 2014 3:53 pm    Post subject: Aug 18 VH Reply with quote

An easy "very hard" in that it wasn't very time consuming for me.

Fascinating puzzle. It started to fall into place like an "easy". Basics went so far that it seemed to be swimming in possibilities.

I chose an x wing that created an xy wing, but that didn't get far. Then I spotted a twin xy wing, either of which would do, that led to another twin xy wing, but this time only one helped. By "twin" I mean two xy wings on the same 3 digits that share two cells.

A surprising 4 stepper, considering how far the basics went.

I'm up after midnight taking advantage of my time zone every now and then to post first, but I won't go all the way today. Instead, I look forward to seeing who can come up with fewer steps, perhaps even only 1.
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hughwill



Joined: 05 Apr 2010
Posts: 215
Location: Birmingham UK

PostPosted: Sun Aug 17, 2014 6:13 pm    Post subject: Aug 18 VH Reply with quote

About time there was a VH. Not that it's Monday yet here, but I bet
it can be done with a
Quote:
X wing on 2 c35

followed by a
Quote:
238 XY-Wing pivot r9c4


I'll have to wait until tomorrow to see if my predictions are correct! Very Happy

Hugh

(I'd post my prediction of an 'after basics' grid but somebody might
smell a rat.......)
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Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Mon Aug 18, 2014 3:45 am    Post subject: Reply with quote

Same as Hugh but my pivot was in r8c5.
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hughwill



Joined: 05 Apr 2010
Posts: 215
Location: Birmingham UK

PostPosted: Mon Aug 18, 2014 9:12 am    Post subject: Aug 18 VH Reply with quote

After Basics:
Code:

+-----------+-------------+-----------+
| 3 28   6  | 9    1  5   | 7 4   28  |
| 5 1    27 | 4    23 378 | 9 6   238 |
| 4 278  9  | 27   6  378 | 1 238 5   |
+-----------+-------------+-----------+
| 1 6    5  | 3    8  9   | 2 7   4   |
| 2 9    8  | 6    7  4   | 3 5   1   |
| 7 4    3  | 1    5  2   | 8 9   6   |
+-----------+-------------+-----------+
| 8 2357 1  | 257  4  37  | 6 23  9   |
| 9 2357 27 | 2578 23 6   | 4 1   238 |
| 6 23   4  | 28   9  1   | 5 238 7   |
+-----------+-------------+-----------+

Play this puzzle online at the Daily Sudoku site

Marty R said:
Quote:
Same as Hugh but my pivot was in r8c5.


As always is the case, you are correct and I have been sloppy!
Embarassed
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arkietech



Joined: 31 Jul 2008
Posts: 1727
Location: Northwest Arkansas USA

PostPosted: Mon Aug 18, 2014 11:42 am    Post subject: Reply with quote

Code:
 *-----------------------------------------------------------*
 | 3     28    6     | 9     1     5     | 7     4     28    |
 | 5     1     27    | 4     23    378   | 9     6     238   |
 | 4     278   9     | 27    6     378   | 1     238   5     |
 |-------------------+-------------------+-------------------|
 | 1     6     5     | 3     8     9     | 2     7     4     |
 | 2     9     8     | 6     7     4     | 3     5     1     |
 | 7     4     3     | 1     5     2     | 8     9     6     |
 |-------------------+-------------------+-------------------|
 | 8     2357  1     | 257   4     37    | 6     23    9     |
 | 9     2357  27    | 2578 a23    6     | 4     1    d28-3  |
 | 6     23    4     |b28    9     1     | 5    c238   7     |
 *-----------------------------------------------------------*
(3=2)r8c6-(2=8)r9c4-r9c8=8r8c9 => -3r8c9; ste

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Clement



Joined: 24 Apr 2006
Posts: 684
Location: Dar es Salaam Tanzania

PostPosted: Mon Aug 18, 2014 12:35 pm    Post subject: Aug 18 VH Reply with quote

Code:

+-----------+-------------+-----------+
| 3 c28   6  | 9    1  5   | 7 4   d28  |
| 5 1    b27 | 4    23 378 | 9 6   238 |
| 4 278  9  | 27   6  378 | 1 238 5   |
+-----------+-------------+-----------+
| 1 6    5  | 3    8  9   | 2 7   4   |
| 2 9    8  | 6    7  4   | 3 5   1   |
| 7 4    3  | 1    5  2   | 8 9   6   |
+-----------+-------------+-----------+
| 8 2357 1  | 257  4  37  | 6 23  9   |
| 9 2357 a27 | 2578 #23 6   | 4 1   *38-2 |
| 6 23   4  | *28   9  1   | 5 23-8 7   |
+-----------+-------------+-----------+
Another two stepper
Kite on 2 originating from BOX 1 (2=7)r8c3-(7=2)r2c3-(2=8)r1c2-8=2)r1c9; r8c9<>2 opens
XY-Wing 23-8 pivoted in r8c5; r9c8<>8; stte.
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dongrave



Joined: 06 Mar 2014
Posts: 54

PostPosted: Tue Aug 19, 2014 11:53 pm    Post subject: Reply with quote

After solving this one using standard VH moves, I went back and examined it for a long time and eventually found two other chains that solve it in one step but neither of them are as short (so consequently not as nice) as Arkietech's solution. One of them is similar to a recent JC Van Hay solution that he referred to as 'nice' in his response to one of Keith's posts and I'm wondering how it should look in Eureka notation. In 'non-Eureka' notation it could be described as follows: r9c4 = 2 or 8; if it's 2, then r8c5=3 -> r8c9<3> r2c9=3; if it's 8, then r9c8<8> r8c9=8 -> r2c9=3; therefore r2c9=3. How do write this out in Eureka notation? Do you just list the sub-expressions for each starting number separated by semicolons and then end it with '=> r2c9=3'? Thanks in advance, Don. Oh! By the way, you know what I noticed? It sure is a lot easier to find chains if you already know the solution!
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rmireland



Joined: 21 Sep 2013
Posts: 15
Location: New Orleans

PostPosted: Wed Aug 20, 2014 3:57 am    Post subject: Reply with quote

I agree with dongrave and have also noticed how easy it is to find chains when working backwards. I would also appreciate a link to a Eureka syntax source to know how to exactly translate my "either this or that" logic into Eureka.
Another point, if I may. If I don't already know the answer, and I am just working with a bi-value cell and tracing the consequences of the two possible values to find common eliminations or contradictions, how is that not "trial and error"?
And maybe it's asking a lot, but I would love for someone (like Clement, maybe) to translate this verbatem into plain English: (2=7)r8c3-(7=2)r2c3-(2=8)r1c2-8=2)r1c9; r8c9<>2
In an ideal world, if I have the chain above, shouldn't I be able to, from the chain alone, determine the final elimination without reference to the puzzle?
I know I ask a lot of questions. It's just my nature.
Thanks, Rick
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Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Wed Aug 20, 2014 5:05 am    Post subject: Reply with quote

Quote:
If I don't already know the answer, and I am just working with a bi-value cell and tracing the consequences of the two possible values to find common eliminations or contradictions, how is that not "trial and error"?


It is as far as I and many others are concerned.

Quote:
And maybe it's asking a lot, but I would love for someone (like Clement, maybe) to translate this verbatem into plain English: (2=7)r8c3-(7=2)r2c3-(2=8)r1c2-8=2)r1c9; r8c9<>2


Eureka notation is the standard way of telling the reader about the solution path. That'd make for a long sentence. It's up to you to learn the notation. I waited way too long to learn notation and was tired of asking questions that were answered by the notation. It just reached the point where I had to learn or be perpetually confused.

Quote:
In an ideal world, if I have the chain above, shouldn't I be able to, from the chain alone, determine the final elimination without reference to the puzzle?


I don't understand the question. Sorry.
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dongrave



Joined: 06 Mar 2014
Posts: 54

PostPosted: Wed Aug 20, 2014 12:31 pm    Post subject: Reply with quote

Quote:
In an ideal world, if I have the chain above, shouldn't I be able to, from the chain alone, determine the final elimination without reference to the puzzle?


I don't understand the question. Sorry.[/quote]

I understand exactly what Rick's saying Marty! He's pointing out that had Eureka been designed right, one would be able to read the expression and understand it without having to refer back to the puzzle in order to decrypt it. The reason I understand this is because that's exactly how I learned it. You probably remember not too long ago when I complained to you about how much I despised it. You pointed out that whether or not I liked it, it's the language that's being used by many experts so I broke down and studied it (even though I grumbled the entire time). Now I can read other's expressions and understand them but I'm still uncertain sometimes when I'm trying to formulate my own expressions - especially for chains like the one I listed in this thread or for coloring solutions. Thanks, Don.
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Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Wed Aug 20, 2014 12:59 pm    Post subject: Reply with quote

Quote:
I understand exactly what Rick's saying Marty! He's pointing out that had Eureka been designed right, one would be able to read the expression and understand it without having to refer back to the puzzle in order to decrypt it.


I don't understand enough about Eureka to defend it or knock it. But as to "...had Eureka been designed right...", how is the present design wrong and what should be changed to make it "right"?
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dongrave



Joined: 06 Mar 2014
Posts: 54

PostPosted: Wed Aug 20, 2014 2:22 pm    Post subject: Reply with quote

Hi Marty, It sounds like you took offense to my bashing of Eureka. (I didn't mean to hit a nerve.) I thought that the rest of my sentence explained what was wrong with it - and that is that it's not intuitive. The fact that people capable of solving the most advanced puzzles in the world (like Keith and Van Hay) are not using it speaks volumes. And the fact that people (like Rick and me) are begging for someone to explain it illustrates just how cryptic it is. The most confusing (and flat out 'wrong' in my mind) was the use of the '=' to denote something completely different than what the entire world knows it to mean. And then enclosing 2 numbers along with it in parentheses at the beginning of each component of an expression takes the word 'cryptic' to a whole new level. Conciseness is not everything. They really should have given some regard to making it more intuitive. Thanks, Don.
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Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Wed Aug 20, 2014 3:32 pm    Post subject: Reply with quote

Quote:
Hi Marty, It sounds like you took offense to my bashing of Eureka.


Nope, you misread me. You'd have to say something a lot stronger that Eureka criticism to offend me.

I'd be more than happy to answer Eureka questions you may have, including the meaning of "=" and "-'.

If you want to ask questions, probably best to do it offline, so PM me if you want to start a Eureka dialogue.
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rmireland



Joined: 21 Sep 2013
Posts: 15
Location: New Orleans

PostPosted: Wed Aug 20, 2014 4:39 pm    Post subject: Reply with quote

Hi Marty and Don,
Please don't go offline for this.
Before seeing the most recent post here, I have just posted to the AUG 20 VH in hopes of continuing this discussion there.
If you think this is not of general interest, then could we start a thread somewhere, please!
Rick
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dongrave



Joined: 06 Mar 2014
Posts: 54

PostPosted: Wed Aug 20, 2014 6:49 pm    Post subject: Reply with quote

That sounds great to me Rick - but of course it's up to Marty! I'm glad I didn't offend him. I thought for a minute that maybe he was involved in the design - and here I was bashing it. Even though I despise it, that doesn't mean that I don't want to learn it! I'll check back in a little while and see what Marty says! Thanks, Don.
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Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Wed Aug 20, 2014 7:13 pm    Post subject: Reply with quote

I was hardly involved in the design; in fact I was years late in learning it.

If you have any questions or comments that are general and don't involve a specific puzzle, then post in the Solving techniques, and terminology sub-forum.
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