exocet pattern in hardest puzzles

Advanced methods and approaches for solving Sudoku puzzles

Re: exocet pattern in hardest puzzles

Postby David P Bird » Thu Jul 26, 2012 10:23 pm

ronk wrote:"An opening post?" The "JExocet" discussion had been in this thread since you introduced the term in mid-April. A separate thread 3 months ago might have been a good idea, but not now IMO. If we start another thread now, where is the "JExocet" discussion supposed to continue?

In two previous posts I have written:
'It's getting to the time when we should consider how to summarise or index our work on JExocets in this and other threads.'
and
'I suggest that we open an Exocet/JExocet Summary thread starting with the agreed definition and followed with links to the examples different contributors have found.'

Why is it that only now, at the third time I've raised the subject, do you finally give any sort of response?

As this thread is now 24 pages long it's difficult for newcomers to find the results of our labours. Consider too that Sudopedia is virtually defunct. What I had in mind was something like <this>. I could only achieve this in separate thread, but as moderator maybe you could insert something at the head of this one.

I believe we should at least do something though, which I'll now leave for your consideration.
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Re: exocet pattern in hardest puzzles

Postby ronk » Thu Jul 26, 2012 10:26 pm

For my ignored pattern here, I coin the BExocet term, i.e., exocet with Bonus. :D
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Re: exocet pattern in hardest puzzles

Postby daj95376 » Thu Jul 26, 2012 10:52 pm

I volunteer to drop posting QExocet/qExocet solutions. That should help reduce the confusion level
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Re: exocet pattern in hardest puzzles

Postby Leren » Fri Jul 27, 2012 1:25 am

With respect to David P Bird's latest comments on puzzle 23333, although all the base digits satisfy the house counting procedure there is no underlying Swordfish pattern for digit 3, so you can't make Swordfish eliminations for that digit.

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Re: exocet pattern in hardest puzzles

Postby ronk » Fri Jul 27, 2012 2:15 am

David P Bird wrote:As this thread is now 24 pages long it's difficult for newcomers to find the results of our labours. Consider too that Sudopedia is virtually defunct. What I had in mind was something like <this>. I could only achieve this in separate thread, but as moderator maybe you could insert something at the head of this one.

I believe we should at least do something though, which I'll now leave for your consideration.

My recommendation: As you suggest, post your JExocet definition and indices in this thread. Then, near the top of his opening post, champagne (or a moderator) can highlight your "post titles" with clickable links to these post(s).
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Re: exocet pattern in hardest puzzles

Postby champagne » Fri Jul 27, 2012 5:23 am

ronk wrote:
David P Bird wrote:As this thread is now 24 pages long it's difficult for newcomers to find the results of our labours. Consider too that Sudopedia is virtually defunct. What I had in mind was something like <this>. I could only achieve this in separate thread, but as moderator maybe you could insert something at the head of this one.

I believe we should at least do something though, which I'll now leave for your consideration.

My recommendation: As you suggest, post your JExocet definition and indices in this thread. Then, near the top of his opening post, champagne (or a moderator) can highlight your "post titles" with clickable links to these post(s).


I have no problem, if ronk can do that to dedicate post 7 reserved in the thread "exotic pattern a resume" to david and to use it.

variations around that idea could be studied
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Re: exocet pattern in hardest puzzles

Postby champagne » Fri Jul 27, 2012 5:28 am

daj95376 wrote:
champagne wrote:I confess I did not look at the prerequisite, but your remark surprises me.

The additional exocets share the base of your's. How can it be that a condition on the base cells is ok on one side and not on the other!!!

There is something I don't catch

I corrected my above post to use QExocet instead of Exocet. My analyzer finds one "additional" QExocet per puzzle ... as opposed to the three additional Exocets that your solver finds. Here is my analyzer's output without ronk's restriction. You'll notice that the QExocets don't share the same base set.

[code]98.7..6....5.9........8..4.83..6.7.....3....6.....7...67...98....2.........6....1;2715



My wording was not quite correct.

We clearly have 2 bases in each of the 2 puzzles.

My point was that, for each base, when you write Target = r7c5==r5c6
my solver express that as a separate exocet.

Not a key point
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Re: exocet pattern in hardest puzzles

Postby David P Bird » Fri Jul 27, 2012 10:51 am

Leren thanks again. I've made a further edit to the definition.

champagne thanks for the offer. I'll let ronk decide which way to go.
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Re: exocet pattern in hardest puzzles

Postby ronk » Fri Jul 27, 2012 11:16 am

champagne wrote:
ronk wrote:My recommendation: As [ronk edit: David P Bird suggests], post your JExocet definition and indices in this thread. Then, near the top of his opening post, champagne (or a moderator) can highlight your "post titles" with clickable links to these post(s).

I have no problem, if ronk can do that to dedicate post 7 reserved in the thread "exotic pattern a resume" to david and to use it.
variations around that idea could be studied

It's mpossible for me to change ownership of posts. Even if I could, IMO there should still be a link to it in your opening post.

Leren wrote:With respect to David P Bird's latest comments on puzzle 23333 ...

Did you mean puzzle 25333?
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Re: exocet pattern in hardest puzzles

Postby Leren » Fri Jul 27, 2012 11:49 am

ronk,

Yes the puzzle number is 25333 - from daj95376's post on p18 of this thread.

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Re: exocet pattern in hardest puzzles

Postby champagne » Fri Jul 27, 2012 2:41 pm

David P Bird wrote:Junior Exocet Definition


David, I had a look to that text and have some comments/questions




b) (JE+) must overlap an Almost Hidden Set that that restricts the object cells to holding one base digit.
The simplest and most frequent situation will be when the AHS is an Almost Hidden Pair with a single extra digit locked in the object cells.



a) "that that" seems to be a typo
b) I don't see any other possibility that having a candidate locked in the object pair to form an AHS




Code: Select all
                                    v           v                         v   
r4   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r5   . . O | O . . | O . . <    . . O | \ . . | O . .     . . O | O . . | O . . <   
r6   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r7   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r8   . . O | O . . | O . . <    . . O | \ . . | O . .     . . \ | \ . . | O . .   
r9   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .
      2 Parallel Lines(I)        2 Parallel Lines(II)      2 Orthogonal Lines
         rows 5 & 8                 columns 3 & 7             row 5 & column 7


I have difficulties with these diagrams.
First one is ok,
In the second and third one, I can't see the possibility to have so many occurrences of the digit.
I don't see clearly the case where the cross line in stack 1 is empty and Q;R is forced in stacks 2 and 3.

For me the logic is something as

stacks 2;3 force stack 1 empty (diagram 1)
stack 1 empty forces one object to be true
stacks 2;3 forces one object to be true

it's more in that way that my code is working


In JE+ patterns (relying on condition 2b) the identity if the target cell won't be known. One object cell must eventually hold a base digit, and the other a candidate locked in the AHS, so any candidates that aren't in either set can be eliminated from both the object cells.


seems to be a typo => the identity of
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Re: exocet pattern in hardest puzzles

Postby David P Bird » Fri Jul 27, 2012 6:18 pm

champagne, thanks for spotting some obvious typos - I'm useless at proof reading my own work.

Now to the points of logic you raise:

I don't see any other possibility that having a candidate locked in the object pair to form an AHS
Look at ronk's extreme example < here >. There is an Almost Hidden Set (578+x)r2358c7. The object cell pair r34c7 must contain a base digit (1234) and a digit locked in the hidden set (578) so (69) can be eliminated from these cells.

I have difficulties with these diagrams.
First one is ok,
In the second and third one, I can't see the possibility to have so many occurrences of the digit.

Yes, they are both impossible as there wouldn't be enough givens to make them solvable. However, individually, every one of the cells shown could be occupied.

I don't see clearly the case where the cross line in stack 1 is empty and Q;R is forced in stacks 2 and 3.
That's impossible as then the digit would be excluded from the base cells if I understand you correctly.
When I edited the definition to fix the typos you found, I added a brief proof to justify the eliminations which covers that.

BTW Aren't you being a little extravagant with the space your posts consume?
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Re: exocet pattern in hardest puzzles

Postby daj95376 » Fri Jul 27, 2012 7:36 pm

Maybe a slightly different perspective of David P. Bird's scenarios.

Code: Select all
                                    v           v                         v   
r4   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r5   . . O | O . . | O . . <    . . O | \ . . | O . .     . . O | O . . | O . . <   
r6   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r7   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .   
r8   . . O | O . . | O . . <    . . O | \ . . | O . .     . . \ | \ . . | O . .   
r9   . . \ | \ . . | \ . .      . . O | \ . . | O . .     . . \ | \ . . | O . .
      2 Parallel Lines(I)        2 Parallel Lines(II)      2 Orthogonal Lines
         rows 5 & 8                 columns 3 & 7             row 5 & column 7

When the base cells are assumed true for a candidate, one of these patterns must follow for a JExcoet:

Code: Select all
 2 Parallel Lines(I):   alternate perspective ...

 to prevent 2-row/3-column contradiction: "Q" or "R" true
 *-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q . . | R . . |
 | - - - | Q . . | R . . |
 *-------*-------*-------*
 | . . / | / . . | / . . |
 | . . S | S . . | S . . |
 | . . / | / . . | / . . |
 *-------*-------*-------*
 | . . / | / . . | / . . |
 | . . S | S . . | S . . |
 | . . / | / . . | / . . |
 *-------*-------*-------*

Code: Select all
 2 Parallel Lines(II):   alternate perspective ...

 "Q" is forced to contain the candidate in [c4]
 *-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q . . | R . . |
 | - - - | Q . . | R . . |
 *-------*-------*-------*
 | . . S | / . . | S . . |
 | . . S | / . . | S . . |
 | . . S | / . . | S . . |
 *-------*-------*-------*
 | . . S | / . . | S . . |
 | . . S | / . . | S . . |
 | . . S | / . . | S . . |
 *-------*-------*-------*

Code: Select all
 2 Orthogonal Lines:   alternate perspective ...

 "Q" is forced to contain the candidate
 X-Chain: r5c3 - r5c4 = r23c4
 *-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q . . | R . . |
 | - - - | Q . . | R . . |
 *-------*-------*-------*
 | . . / | / . . | S . . |
 | . . S | S . . | S . . |
 | . . / | / . . | S . . |
 *-------*-------*-------*
 | . . / | / . . | S . . |
 | . . / | / . . | S . . |
 | . . / | / . . | S . . |
 *-------*-------*-------*

A common sub-case of the first scenario.

Code: Select all
 X-Chain: r23c4 = r5c4 - r5c3 = r8c3 - r8c7 = r23c7
 *-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q . . | R . . |
 | - - - | Q . . | R . . |
 *-------*-------*-------*
 | . . / | / . . | / . . |
 | . . S | S . . | / . . |
 | . . / | / . . | / . . |
 *-------*-------*-------*
 | . . / | / . . | / . . |
 | . . S | / . . | S . . |
 | . . / | / . . | / . . |
 *-------*-------*-------*



Note: there is a rare scenario that DPB's scenarios don't cover. (the distinction between QExocet and JExocet.)

Code: Select all
 "Q" is forced to contain the candidate
 *-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q / / | R . . |
 | - - - | Q / / | R . . |
 *-------*-------*-------*
 | . . S | S . . | S . . |
 | . . S | S . . | S . . |
 | . . S | S . . | S . . |
 *-------*-------*-------*
 | . . S | S . . | S . . |
 | . . S | S . . | S . . |
 | . . S | S . . | S . . |
 *-------*-------*-------*
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Re: exocet pattern in hardest puzzles

Postby champagne » Sat Jul 28, 2012 5:10 am

David P Bird wrote:BTW Aren't you being a little extravagant with the space your posts consume?


By the way this sounds very bad in French

Nevertheless, a last tentative contribution to your jexocet definition.

Code: Select all
*-------*-------*-------*
 | B B - | - - - | - - - |
 | - - - | Q . . | R . . |
 | - - - | Q . . | R . . |
 *-------*-------*-------*
 | . . 0 | . . . | . . . |
 | . . . | 0 . . | 0 . . |
 | . . . | . . . |. . . |
 *-------*-------*-------*
 | . . . | . . . | . . . |
 | . . 0 |. . . | . . . |
 | . . 0 | . . . | . . . |
 *-------*-------*-------*

in such a situation, the jexocet is established.

I don't see how it fits with your diagrams
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Re: exocet pattern in hardest puzzles

Postby David P Bird » Sat Jul 28, 2012 6:05 am

champagne, sorry if my comment is rude in French!

I think I can understand your problem, the three diagrams in the definition are only examples, they don't cover every possibility – I'll make that clear.

In your last post, the instances of the digit in the 'S' cells are all covered by column 3 and row 5 and therefore satisfy the condition.
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