Is this a new technique?

Advanced methods and approaches for solving Sudoku puzzles

Is this a new technique?

Postby RobO » Mon Feb 16, 2009 8:57 pm

Is this a new technique? Although I think it will fall into aligned pair exclusions and almost locked sets, it seems to me to be far simpler and, dare I say, more elegant, than those. I certainly don't remember seeing it documented anywhere else.

It's kind of a cross between a y-wing and an xyz-wing so, for now, I'm calling it the xy2z wing (where the 2 is supposed to be the smaller raised 'squared' variety).

http://forums.websudoku.com/tool/view/mb/file?username=websudoku&id=737610

Logic goes: if B6 is a 3, then B7 must be an 8. And if B6 is a 2, then you have a naked pair of 89s on the top row. Either way, B5 cannot be an 8.
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Postby Pat » Mon Feb 16, 2009 9:13 pm

hi RobO,

please post your example as text

Code: Select all
 6 7 3   . . 5
 . . .   7 . .
 . 5 8   . . .

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Postby RobO » Mon Feb 16, 2009 9:30 pm

Apologies if I have done something against the way that this board works. What format do I use to include possiblities for unsolved cells?

If I post just the solved cells, then there are a couple of more complex techniques - x-cycles - that get me to my position. Is that going to cause a problem?
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Postby Pat » Mon Feb 16, 2009 9:44 pm

sure, put several possibilities in any cell,
just make sure to get everything aligned (using blank spaces)
Code: Select all
 6       147     1237    |  13      479     5       |  379     8       279
 23457   147     123578  |  13      4789    789     |  35679   579     2679
 357     9       3578    |  2       6       78      |  357     4       1
 ------------------------+--------------------------+----------------------
 8       16      1269    |  7       5       29      |  19      3       4
 79      5       4       |  8       1       3       |  2       6       79
 279     3       127     |  4       29      6       |  8       179     5
 ------------------------+--------------------------+----------------------
 1       8       5679    |  56      3       4       |  5679    2       679
 34579   467     35679   |  56      27      127     |  145679  1579    8
 457     2       567     |  9       78      178     |  14567   157     3

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Postby RobO » Mon Feb 16, 2009 10:09 pm

Think I've got it with no typos. What's the problem with hyperlinks? Just that they can't be imported into programs?

Code: Select all
 6       7       3       |  289     289     5       |  4       289     1
 124     19      49      |  7       248     23      |  38      5       6
 24      5       8       |  12369   12469   123469  |  7       239     29
 ------------------------+--------------------------+----------------------
 8       19      7       |  129     3       124     |  5       6       249
 34      6       5       |  29      7       8       |  1       239     249
 134     2       49      |  5       1469    1469    |  38      389     7
 ------------------------+--------------------------+----------------------
 7       4       6       |  2389    289     239     |  29      1       5
 59      8       2       |  4       156     169     |  69      7       3
 59      3       1       |  269     256     7       |  269     4       8

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Postby Pat » Mon Feb 16, 2009 10:32 pm

RobO wrote:What's the problem with hyperlinks?
Just that they can't be imported into programs?
    links are fine
      (as long as they remain valid.
      too often the target vanishes---)
the problem is with images --
when i wish to comment on your puzzle,
do you expect me to mark up your image?
(and note, images cannot be uploaded to our forum)
    whereas with text,
    i can flag certain cells
    and remove certain possibilities etc
and yes, i wish to paste the puzzle into my favourite solver-software
(e.g. Simple Sudoku)
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Postby RobO » Mon Feb 16, 2009 11:07 pm

Fair enough. The one about hosted images disappearing would, I see now, be potentially very frustrating.
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Postby hobiwan » Tue Feb 17, 2009 12:27 am

Hi RobO,

I think your move is best described as
Code: Select all
Almost Locked Set XY-Wing: A=r1c45 - {289}, B=r2c7 - {38}, C=r2c6 - {23}, X,Y=2,3, Z=8 => r1c8,r2c5<>8

or
Code: Select all
Almost Locked Set XZ-Rule: A=r1c45 - {289}, B=r2c67 - {238}, X=2, Z=8 => r1c8,r2c5<>8
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Postby RobO » Tue Feb 17, 2009 2:16 am

hobiwan wrote:Hi RobO,

I think your move is best described as
Code: Select all
Almost Locked Set XY-Wing: A=r1c45 - {289}, B=r2c7 - {38}, C=r2c6 - {23}, X,Y=2,3, Z=8 => r1c8,r2c5<>8

or
Code: Select all
Almost Locked Set XZ-Rule: A=r1c45 - {289}, B=r2c67 - {238}, X=2, Z=8 => r1c8,r2c5<>8


True. But you could also take any of the basic techniques and express them as a case of a more complex one. e.g. a y-wing being just a short y-chain, or a naked pair being the other side of hidden quintuple. Where do we choose to draw the line?

I actually found this pattern while scanning for y-wings. While checking for a 28 to go with the 23/38 cells I noticed the pair of 289s and it didn't take long to realise that it could eliminate the 8. I have also read descriptions of almost locked sets, but without fully understanding them (I think I may have got over that barrier today). For reference, I'm at the stage where I'm applying x-cycles, finned x-wings and swordfish, and hidden rectangles.

I would suggest that the pattern in my example is spottable by someone with far less skill than is required to start understanding the intricacies of almost locked sets.

(...and, of course, I love the idea of having a new technique where I'm credited as the first to point it out.)
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Postby StrmCkr » Tue Feb 17, 2009 2:48 am

another
view is a kraken cell.

(2)R2C6 =(89)R1C45(hp)
|
(3)R2C6 =(8)R2C7
|
=> R2C5<>8, R1C8<>8

which could be written as an AIC as well..

the problem with nameing every variation of the same type of move is mass confusion,
you dont need a name for everything.

when it already is explained by several others types of moves.

but if its unique specific inferences then perhaps it does need a name.

im also pretty sure this sequence was pointed out long ago on here..
under:
als+ xy

but despite all the above
good find:)
a very good example of the princliples in forming an extened als
Last edited by StrmCkr on Tue Feb 17, 2009 1:45 am, edited 1 time in total.
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Postby DonM » Tue Feb 17, 2009 3:38 am

RobO wrote:
hobiwan wrote:Hi RobO,

I think your move is best described as
Code: Select all
Almost Locked Set XY-Wing: A=r1c45 - {289}, B=r2c7 - {38}, C=r2c6 - {23}, X,Y=2,3, Z=8 => r1c8,r2c5<>8

or
Code: Select all
Almost Locked Set XZ-Rule: A=r1c45 - {289}, B=r2c67 - {238}, X=2, Z=8 => r1c8,r2c5<>8


True. But you could also take any of the basic techniques and express them as a case of a more complex one. e.g. a y-wing being just a short y-chain, or a naked pair being the other side of hidden quintuple. Where do we choose to draw the line?


It seems to occur frequently that newer solvers find relationships that are expressed in already-discovered well-known and accepted techniques and those solvers not knowing about those techniques feel that their technique should be accepted as either something new or an accepted alternative. The problem with this is that you potentially end up with all sorts of techniques with various names that do the same thing which results in a lot of confusion for other new solvers. There has to be some sort of accepted standard basic techniques in order for there to be useful tutorials & even books on the subject.

I have also read descriptions of almost locked sets, but without fully understanding them (I think I may have got over that barrier today). For reference, I'm at the stage where I'm applying x-cycles, finned x-wings and swordfish, and hidden rectangles. I would suggest that the pattern in my example is spottable by someone with far less skill than is required to start understanding the intricacies of almost locked sets.

(...and, of course, I love the idea of having a new technique where I'm credited as the first to point it out.)


It takes some clever reasoning to come up with something like this on your own, but I would suggest that only when you become more familiar with ALSs will you be able to say for sure which approach is more 'spottable'. However, one can always describe the technique more clearly with a text-based (of even image-based) example and try to make a case for why the suggested technique is better than the traditional one(s).
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Postby RobO » Tue Feb 17, 2009 8:12 am

So the best I get is a "good example"? Ah well, I can live with that.

I'd still say though that my example is understandable by the huddled masses, while almost locked sets aren't. There's a major difference that I think you guys are too far advanced to notice.
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Postby tarek » Tue Feb 17, 2009 8:21 am

RobO,

If you think that your representation is easier to explain then give us a better effort to persuade us.

Somebody worked very hard to demonstrate that a Skyscraper & a 2-string kite are easier on the eye than techniques that subsume them:D

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Postby StrmCkr » Tue Feb 17, 2009 8:21 am

not perticular:)

i dont think we have missed the point.

you have a none complex version of a move set
known as
extended als.(als-xy) or als-xz rule
and its
very nice.

why make it have another name?

when it is
utilizing a three digit set in three cells (als) with two bivalvues linked.
: thus either choices of the two digits in either of the bivalves locks the 8. via the als.

or how i posted it..

2 leaves the 89 pair.
or 3 sets the 8. => any cell that sees both outcomes <>8

pretty simple.

but as tarek says persuade us:)
and it could be other wise.
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Postby DonM » Tue Feb 17, 2009 9:00 am

RobO wrote:I'd still say though that my example is understandable by the huddled masses, while almost locked sets aren't. There's a major difference that I think you guys are too far advanced to notice.


Ah, another life lesson: There is ignorance in knowing too much!:D

tarek wrote:RobO,

If you think that your representation is easier to explain then give us a better effort to persuade us. Somebody worked very hard to demonstrate that a Skyscraper & a 2-string kite are easier on the eye than techniques that subsume them:D

tarek


That's an excellent example. Havard never tried to sell those patterns over the one's they replace. He simply presented them as patterns that he felt worked better for him and gave a number of excellent examples to indicate why. That's what sold them to everyone else.
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