The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |.38|.9.|2..|
 |.4.|.16|...|
 |51.|8..|...|
 |---+---+---|
 |..3|...|..1|
 |.81|...|76.|
 |2..|...|8..|
 |---+---+---|
 |...|..8|.93|
 |...|16.|.2.|
 |..6|.7.|18.|
 *-----------*


Play/Print this puzzle online

[Leren]

Code: Select all

*-----------------------------------------------------*
| 6    3    8     | 457  9    457   | 2    1    45    |
|e79   4    279   | 235  1    6     | 39   5-7  8     |
| 5    1    29-7  | 8    23  a24    | 39  b47   6     |
|-----------------+-----------------+-----------------|
|d79   679  3     | 267  8   c27    | 45   45   1     |
| 4    8    1     | 359  35   59    | 7    6    2     |
| 2    567  57    | 67   4    1     | 8    3    9     |
|-----------------+-----------------+-----------------|
| 1    257  457   | 245  25   8     | 6    9    3     |
| 8    59   459   | 1    6    3     | 45   2    7     |
| 3    25   6     | 2459 7    2459  | 1    8    45    |
*-----------------------------------------------------*

xy-wing (247) with pincer transport => -7 r2c8, r3c3; stte

Leren

[pjb]

Code: Select all

 6      3      8     | 457    9      457    | 2      1      45     
c79     4      279   | 235    1      6      | 39     57     8     
 5      1     d279   | 8     d23     4-2    |d39     47     6     
---------------------+----------------------+---------------------
b79     679    3     | 267    8     a27     | 45     45     1     
 4      8      1     | 359    35     59     | 7      6      2     
 2      567    57    | 67     4      1      | 8      3      9     
---------------------+----------------------+---------------------
 1      257    457   | 245    25     8      | 6      9      3     
 8      59     459   | 1      6      3      | 45     2      7     
 3      25     6     | 2459   7      2459   | 1      8      45     


(2=7) r4c6 - (7=9) r4c1 - (9=7) r2c1 - (7=239) r3c357 => r3c6 <> 2; stte

Phil

[7b53]

xy-wing (247) with pincer transport => -7 r2c8, r3c3; stte

what's the difference between this and an xy-chain ?

[Marty R.]

xy-wing (247) with pincer transport => -7 r2c8, r3c3; stte

what's the difference between this and an xy-chain ?

Really nothing since an XY-Wing is a three-cell XY-Chain but we don't call it that, we use the Wing designation. I don't know the history of why the terminology is what it is.

[Marty R.]

Code: Select all

+------------+--------------+----------+
| 6  3   8   | 457  9  457  | 2  1  45 |
| 79 4   279 | 235  1  6    | 39 57 8  |
| 5  1   279 | 8    23 24   | 39 47 6  |
+------------+--------------+----------+
| 79 679 3   | 267  8  27   | 45 45 1  |
| 4  8   1   | 359  35 59   | 7  6  2  |
| 2  567 57  | 67   4  1    | 8  3  9  |
+------------+--------------+----------+
| 1  257 457 | 245  25 8    | 6  9  3  |
| 8  59  459 | 1    6  3    | 45 2  7  |
| 3  25  6   | 2459 7  2459 | 1  8  45 |
+------------+--------------+----------+


Play this puzzle online at the Daily Sudoku site

I saw the XY-Wing with transport but missed the fact that it finished things off.

Nameless chain (5=9)r8c2-r4c2=r4c1-(9=7)r2c1-(7=5)r2c8-r1c9=r9c9=>r8c7r9c2<>5

[Leren]

xy-wing (247) with pincer transport => -7 r2c8, r3c3; stte

what's the difference between this and an xy-chain ?

The move I had in mind was:

1. (7-4) r3c8 - (4=2) r3c6 - (2=7) r4c6 - r4c1 = r2c1

whereas what you appear to have in mind was:

2. (7-4) r3c8 - (4=2) r3c6 - (2=7) r4c6 - (7=9) r4c1 - (9=7) r2c1

1. Depends only on there being two 7's in column 1 and would still work had there been more than 2 candidates in r2c1 and/or r4c1.

2. Depends on there being a locked pair 7x in r24c1.

Leren

[DonM]

xy-wing (247) with pincer transport => -7 r2c8, r3c3; stte

what's the difference between this and an xy-chain ?

Really nothing since an XY-Wing is a three-cell XY-Chain but we don't call it that, we use the Wing designation. I don't know the history of why the terminology is what it is.

I don't claim to have the best explanation, but having started sudoku fairly early in the game (late 2005/early 2006), my sense is that, in those years, the simpler patterns were found, named and emphasized first and were the ones that would appear in the first sudoku tutorials and the few books on solving methods. I believe that this was because the first puzzles being solved were relatively easy and would tend to have more of these simpler patterns rather than patterns which were larger or a little more complicated, even though closely related.

Unfortunately, the result was that when, as time passed, more difficult puzzles were tackled and these larger patterns became more apparent, they were given names that implied that they were separate/different patterns. So you would have patterns such as xy-wings and xy-chains which are really the same thing and then, even worse, you had the als xz-rule, als xy-wing and als xy-chain which are really all the same thing: als chains.

I may be wrong, but my sense is that the unfortunate 'death' of the Eureka forum and some of the early original Players forum has caused a time warp where sudoku terminology has been set back a few years. For instance, I had lobbied for the term als chains starting several years ago and it appeared to be having some effect, but now it's back to als zx-rule etc. Plus, I have no idea what all these Wing chain names are that virtually didn't exist in regular solving a few years ago and I have no idea what purpose they serve ie. m-wing, h-wing, s-wing etc. (the lone exception being W-wing which IMO does serve a purpose).

(Well, yes, I know the definition of those wing chain names, but I ask, do solvers really start out looking for an m-wing or an h-wing? Maybe they do, but, except for W-wings which I do look for, I just look for chains...)

[Marty R.]

but I ask, do solvers really start out looking for an m-wing or an h-wing? Maybe they do, but, except for W-wings which I do look for, I just look for chains...)

Speaking for myself only, looking for M-Wings is part of my standard routine. I start looking for chains after I look for what I call "pattern-based" solutions. Looking for chains is not fun for me because I can't see them on the grid, so finding them is strictly a trial-and-error process. But since the solution to virtually every posted puzzle is a one-step chain, I play that game to "keep up with the Joneses" and try to post competitive solutions.

But when playing a puzzle just for my own amusement, I find it more satisfying to finish a puzzle with multiple pattern-based steps than a single chain found by trial and error.

[daj95376]

I was first introduced to "extended" and "transport" at the DailySudoku site. Here's my recollection on "transport" vs. XY-Chain for this puzzle.

Code: Select all

 XY-Chain a-b-c-d-e:

 (7-4)r3c8 - (4=2)r3c6 - (2=7)r4c6 - (7=9)r4c1 - (9=7)r2c1  =>  r2c8,r3c3<>7
 +--------------------------------------------------------------+
 |  6     3     8     |  457   9     457   |  2     1     45    |
 | e79    4     279   |  235   1     6     |  39    5-7   8     |
 |  5     1     29-7  |  8     23   b24    |  39   a47    6     |
 |--------------------+--------------------+--------------------|
 | d79    679   3     |  267   8    c27    |  45    45    1     |
 |  4     8     1     |  359   35    59    |  7     6     2     |
 |  2     567   57    |  67    4     1     |  8     3     9     |
 |--------------------+--------------------+--------------------|
 |  1     257   457   |  245   25    8     |  6     9     3     |
 |  8     59    459   |  1     6     3     |  45    2     7     |
 |  3     25    6     |  2459  7     2459  |  1     8     45    |
 +--------------------------------------------------------------+
 # 53 eliminations remain


Code: Select all

 XY-Wing              : vertex = A, pincer_1 = B, pincer_2 = C
 transpost on pincer_2: strong link (7)r4c1 = (7)r2c1

 (7-4)r3c8 - (4=2)r3c6 - (2=7)r4c6 - (7)r4c1 = (7)r2c1  =>  r2c8,r3c3<>7
 +--------------------------------------------------------------+
 |  6     3     8     |  457   9     457   |  2     1     45    |
 | e79    4     279   |  235   1     6     |  39    5-7   8     |
 |  5     1     29-7  |  8     23   A24    |  39   B47    6     |
 |--------------------+--------------------+--------------------|
 | d79    679   3     |  267   8    C27    |  45    45    1     |
 |  4     8     1     |  359   35    59    |  7     6     2     |
 |  2     567   57    |  67    4     1     |  8     3     9     |
 |--------------------+--------------------+--------------------|
 |  1     257   457   |  245   25    8     |  6     9     3     |
 |  8     59    459   |  1     6     3     |  45    2     7     |
 |  3     25    6     |  2459  7     2459  |  1     8     45    |
 +--------------------------------------------------------------+
 # 53 eliminations remain


[DonM]

I think that it was (the much missed) Re'born who first popularized Transport circa '07-'08 with a dedicated article that I think was on Eureka. I have it stored away somewhere. He refers to transport in this thread (read further down in Nov8 post):

http://forum.enjoysudoku.com/bug3-mutant-z-wing-example-t6441.html

[7b53]

would still work had there been more than 2 candidates in r2c1 and/or r4c1.

so...unlike xy-chain which all are bivalue-cells.
the "transport cells" can have 2 or more candidates.

and although the results are the same.
there's a slight difference (meaning)for the two notations.