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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Fri Jun 19, 2009 4:20 pm Post subject: Free Press 19 June, 2009 |
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A tough one.
| Code: | Puzzle: FP061909
+-------+-------+-------+
| . 2 . | . 3 . | . 8 . |
| . . 5 | . 4 9 | . . . |
| . . 7 | . . . | 6 . 4 |
+-------+-------+-------+
| . . . | 3 . . | . . . |
| 5 4 2 | . . . | 3 1 6 |
| . . . | . . 6 | . . . |
+-------+-------+-------+
| 7 . 9 | . . . | 2 . . |
| . . . | 5 2 . | 9 . . |
| . 1 . | . 7 . | 8 5 . |
+-------+-------+-------+ |
Keith |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Fri Jun 19, 2009 5:25 pm Post subject: free press |
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Could not find a single bullet. Norm?
A shotgun solution: finned x-wing eliminates 9 in R4C1, xy-chain eliminates 5 in R4C9, xy-wing (689) eliminates 9 in R1C9.
Earl |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Jun 19, 2009 7:45 pm Post subject: |
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| Code: | .------------------.------------------.------------------.
|*69 2 4 | 16 3 7 | 15 8 59 |
| 368 368 5 | 16 4 9 | 17 *37 2 |
| 1 3-9 7 | 2 8 5 | 6 *39 4 |
:------------------+------------------+------------------:
|*689 *6789 18 | 3 15 2 | 4 *79 589 |
| 5 4 2 | 7 9 8 | 3 1 6 |
| 389 3789 138 | 4 15 6 | 57 2 589 |
:------------------+------------------+------------------:
| 7 5 9 | 8 6 3 | 2 4 1 |
| 4 38 38 | 5 2 1 | 9 6 7 |
| 2 1 6 | 9 7 4 | 8 5 3 |
'------------------'------------------'------------------' |
(9=6)r1c1 - (6)r4c1 = (6-7)r4c2 = (7)r4c8 - (7=3)r2c8 - (3=9)r3c8; r3c2 <> 9 |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Fri Jun 19, 2009 7:46 pm Post subject: |
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How about this?
| Code: | *-----------------------------------------------------------*
| 69 2 4 | 16 3 7 | 15 8 59 |
| 368 368 5 | 16 4 9 | 17 37 2 |
| 1 39 7 | 2 8 5 | 6 39 4 |
|-------------------+-------------------+-------------------|
| 689 6789 18 | 3 15 2 | 4 79 589 |
| 5 4 2 | 7 9 8 | 3 1 6 |
| 389 3789 138 | 4 15 6 | 57 2 589 |
|-------------------+-------------------+-------------------|
| 7 5 9 | 8 6 3 | 2 4 1 |
| 4 38 38 | 5 2 1 | 9 6 7 |
| 2 1 6 | 9 7 4 | 8 5 3 |
*-----------------------------------------------------------*
r1c1=6 r4c2=6
r1c1=9 r4c8=7 => r4c2<>7 |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Jun 19, 2009 8:00 pm Post subject: |
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| arkietech wrote: | How about this?
| Code: | *-----------------------------------------------------------*
| 69 2 4 | 16 3 7 | 15 8 59 |
| 368 368 5 | 16 4 9 | 17 37 2 |
| 1 39 7 | 2 8 5 | 6 39 4 |
|-------------------+-------------------+-------------------|
| 689 6789 18 | 3 15 2 | 4 79 589 |
| 5 4 2 | 7 9 8 | 3 1 6 |
| 389 3789 138 | 4 15 6 | 57 2 589 |
|-------------------+-------------------+-------------------|
| 7 5 9 | 8 6 3 | 2 4 1 |
| 4 38 38 | 5 2 1 | 9 6 7 |
| 2 1 6 | 9 7 4 | 8 5 3 |
*-----------------------------------------------------------*
r1c1=6 r4c2=6
r1c1=9 r4c8=7 => r4c2<>7 |
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in chain form
(7=9)r4c8 - (9)r3c8 = (9)r3c2 - (9=6)r1c1 - (6)r4c1 = (6)r4c2; r4c2 <> 7
good one  |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Fri Jun 19, 2009 8:28 pm Post subject: Free press |
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Norm, Dan, Kieth, etc
Ordinarily I don't like people who are so intelligent, but you guys are the exception. It might be helpful for many if you would explain, or offer a link to, the shorthand of the chain (meaning of =, -, <, etc)
Earl |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jun 19, 2009 10:19 pm Post subject: |
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X-Wing (1), DP (15-18-58), Type 1 UR (38) and W-Wing (79).
As to the DP, in the grids shown, r6c3 must be = 3 or r4c9 or r6c9 must be = 9 in order to break up the DP.
| Quote: | | It might be helpful for many if you would explain, or offer a link to, the shorthand of the chain (meaning of =, -, <, etc) |
I would add to Earl's request to briefly describe the technique in addition to showing the notation, rather than showing notation only. |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Fri Jun 19, 2009 11:49 pm Post subject: |
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I use a shorthand description:
r1c1=6 r4c2=6
r1c1=9 r4c8=7 => r4c2<>7
Which means row 1 col 1 can contain only one of two values, 6 or 9.
If it is 6 then row 4 col 2 must be a 6
If it is 9 then row 4 col 8 must be a 7
=> means therefore
in either condition row 4 col 2 cannot be 7, <>7.
Hope this helps. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat Jun 20, 2009 9:14 am Post subject: |
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here are two good links on Eureka notation.
http://www.sudocue.net/eureka-notation.php
http://www.sudopedia.org/wiki/Eureka
basically what you will find is this
"=" equal sign is the symbol for a strong inference - the values on either side of the symbol can't both be false
A=B; means that if A is false the B must be true AND and if B is false then A must be true
"-" dash is the symbol for a weak inference - the values on either side of the symbol can't both be true
A-B; means that if A is true then B must be false AND if B is true then A must be false
"<>" is my symbol for "not equal" or "eliminates"
A=B-C=D-E=F; simply means that either A is true OR F is true (but not true at the same time). The chain connects A and F. sometimes A and F will be the same candidate, sometimes not. The chain is only useful if any deductions or eliminations can be made when either the beginning value or the ending value is true. this chain also alternates strong/weak inferences and can be read forward and backward and still be logical. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Mon Jun 22, 2009 10:29 am Post subject: |
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| Norm wrote: | | A=B-C=D-E=F; simply means that either A is true OR F is true (but not true at the same time). |
Norm, Norm, Norm,
A=B-C=D-E=F means A=F. That is, A and F have a strong inference, which means that they cannot both be false. It is quite possible that both are true.
This 19Jun09 LAT puzzle had two Sue de Coqs, which I'm surprised no one mentioned. However, I used the 6-cell DP, as Marty mentions ... though from a different point of view and taking note of internal conjugate links:
(5)r4c9 - 6cellDP[(5)r1c9=(8)r8c3] - (8=1)r4c3 - (1=5)r4c5 - (5)r4c9; r4c9<>5
Basically, it's a short XY-Chain plus the DP link. This plus a Turbot Fish on 9 and an XY-Wing was my path.
I'm surprised there is no entry for the 12Jun09 puzzle. It was especially interesting. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Jun 22, 2009 3:57 pm Post subject: |
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I knew I would pull Asellus out of the ashes with a post like this.
| Quote: | Norm, Norm, Norm,
A=B-C=D-E=F means A=F. That is, A and F have a strong inference, which means that they cannot both be false. It is quite possible that both are true.
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see?
you of all the posters to this site knew what I was trying to say and i am glad you chimed in to clarify it.
I was not trying to say that both A and F couldn't be true according to the result of the puzzle. I WAS trying to say that according to the chain either one was true and the other was false and vice versa.
I guess there is the possibility one might not gather that info from the two links I provided?????  |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Jun 22, 2009 9:50 pm Post subject: |
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| A couple of ERs and an x-wing on <9> and it all fell apart. Methinks thou did struggle too much. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Mon Jun 22, 2009 11:56 pm Post subject: |
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| Norm wrote: | | I WAS trying to say that according to the chain either one was true and the other was false and vice versa. |
But the chain DOESN'T say that. The chain only says that they can't both be false. Perhaps your statement derives from the attempt to use assumptions to understand the AIC. IF YOU ASSUME one end is false, the other MUST be true. But, there is no reason to make that assumption. The AIC performs its eliminations in any case.
Thinking in terms of alternating inferences allows us to forget about explicit assumptions. AICs are easier to understand, spot and use when one thinks only of inferences and learns to abandon thinking in terms of assumptions. They are then a purely mechanical technique, just like coloring. In fact AICs are just a special variant of multi-coloring, with the plus that they don't require making color marks on ones grid. (However, multi-coloring is one way to find AICs.) They do, for me at least, require the use of a written notation such as Eureka since it is easier to use the notation than to try to keep track of them in my head. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Jun 23, 2009 4:15 am Post subject: |
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| Quote: | | But the chain DOESN'T say that. The chain only says that they can't both be false |
Asellus, Asellus, Asellus,
I am not arguing what the chain means. I am not arguing what the chain states. I am not even arguing which candidates are strongly inferenced or not.
its amazing how much misunderstanding goes on when all we have to communicate is written words. and when you try and explain logic using written words??? the brain starts to wonder around a little bit, starts to walk off on tangents, just a tad. ya think???
what I am discussing is how the chain is read from left to right and from right to left. I believe that is where the confusion stems from the readers of this forum. The readers want to know what in the world the chain says, and how in the world I am going to read that gosh-darn long thing. right?
A=B-C=D-E=F
when I read this chain from left to right, I say, IN MY HEAD not assuming that A is false, then go on down the chain, etc etc etc. until they get to F being true (not assuming), in that direction.
when I read the chain from right to left, i say, IN MY HEAD, not assuming that F is false, then go on down the chain, etc etc etc.... til they get to A being true (not assuming), in that direction
all I am trying to do here is help the reader understand how the chain should be read. what the reader is actually THINKING in their brains about the chain. that is all !!!
I want the reader to be aware that my AICs are written so that they start with a strong inference and end with a strong inference. and I want the reader of my chain to be aware that regardless from which side of the chain one starts, the reader should start by saying, IN THE MIND, not assuming that the value is false. Doing this will create a revelation in the mind of the reader hopefully shedding light that the chain is infact true in both directions. TADA !!!
for example
if I write this series of strong and weak inferences
(2=3) - (3=4) - (4=2)
one should read from left to right as follows:
"2 is false, 3 is true", etc, on down the chain.
you wouldn't start it:
"2 is true, 3 is false" this will quickly start to make no sense.
then start from right to left.
2 is false, 4 is true, etc, on down the chain.
you wouldn't start it:
"2 is true, 4 is false" this would quickly make no sense either.
the reason you do this, in your mind, is so you can see that the chain does indeed make sense in both directions. I am not at all saying that you should assume that one is true and the other is false. as I have been misinterpreted as saying time and time again. and you know what? I don't mind taking full responsibility for this because I can see the confusion one can get into when trying to keep track of the trane of thought process needed in a sudoku type logic. (try saying that ten times fast). a process that is OBVIOUSLY cared for on this forum and therefore demanded to be treated with utmost clarity and sometimes gets the better of me.  sorry.
Asellus sometimes starts and ends his AICs with the victim candidates, IOW, with weak inferences, in this case, IN YOUR MIND, you would start reading his chains, in your mind, with the first value as true.
if anyone has a better way to explain reading a AIC, please be my guest.
otherwise,
that is my offer for an explanation on reading AICs. an explanation that needs to be addressed in the solving techniques and terminology section. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Jun 23, 2009 5:23 am Post subject: |
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Asellus wrote:
| Quote: | | I'm surprised there is no entry for the 12Jun09 puzzle. It was especially interesting. |
right on cue, Keith posts it. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Jun 23, 2009 5:44 am Post subject: |
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| storm_norm wrote: | Asellus wrote:
| Quote: | | I'm surprised there is no entry for the 12Jun09 puzzle. It was especially interesting. |
right on cue, Keith posts it. |
Posting that puzzle was on my list of things to do. But, I do not have the exclusive franchise. If it is interesting (and missing for a week), please post it yourself!
Keith |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Jun 23, 2009 5:52 am Post subject: |
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| keith wrote: | | storm_norm wrote: | Asellus wrote:
| Quote: | | I'm surprised there is no entry for the 12Jun09 puzzle. It was especially interesting. |
right on cue, Keith posts it. |
Posting that puzzle was on my list of things to do. But, I do not have the exclusive franchise. If it is interesting (and missing for a week), please post it yourself!
Keith |
I didn't mean anything offensive, Keith.
guess my attempt at being funny didn't work.
yet another misunderstanding. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Jun 23, 2009 6:41 am Post subject: |
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| Quote: | | I'm surprised there is no entry for the 12Jun09 puzzle. It was especially interesting. |
Norm,
Given the comment by Asellus, I am surprised that Asellus did not post it. At some point, we may be enlightened as to why it is "especially interesting".
Keith |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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