The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |.3.|64.|.1.|
 |86.|...|4..|
 |...|.5.|.7.|
 |---+---+---|
 |..3|4..|..1|
 |.21|...|95.|
 |9..|..1|7..|
 |---+---+---|
 |.4.|.8.|...|
 |..8|...|.39|
 |.1.|.23|.8.|
 *-----------*


Play/Print this puzzle online

[pjb]

Code: Select all

 257    3      257    | 6      4      9      | 28     1      258   
 8      6      25     | 3      1      7      | 4      9      25     
 1      9      4      | 28     5      28     | 3      7      6     
 ---------------------+----------------------+---------------------
a57    b578    3      | 4      9      2-5    | 268    26     1     
 4      2      1      | 78     67     68     | 9      5      3     
 9      58     6      | 25     3      1      | 7      4      28     
 ---------------------+----------------------+---------------------
 3      4      259    | 159    8     e56     | 1256   26     7     
 2567  c57     8      | 157   d67     4      | 1256   3      9     
 567    1      579    | 579    2      3      | 56     8      4     


(5=7) r4c1 - r4c2 = r8c2 - (7=6) r8c5 - (6=5) r7c6 => -5 r4c6; stte

Phil

[SteveG48]

Code: Select all

.----------------.-------------.---------------.
| 257   3    257 | 6    4   9  | 28    1   258 |
| 8     6    25  | 3    1   7  | 4     9   25  |
| 1     9    4   | 28   5   28 | 3     7   6   |
:----------------+-------------+---------------:
| f57   f578 3   | 4    9   e25| 268   26  1   |
| 4     2    1   | 78   b67 c68| 9     5   3   |
| 9     g58  6   | 25   3   1  | 7     4   28  |
:----------------+-------------+---------------:
| 3     4    259 | 159  8   d56| 1256  26  7   |
| 2567  h57   8  | 157 aI67 4  | 1256  3   9   |
| 567   1    579 | 579  2   3  | 56    8   4   |
'----------------'-------------'---------------'


(6)r8c5 = r5c5 - r5c6 = (6-5)r7c6 = (5)r4c6 - r4c12 = r6c2 - (5=7)r8c2 - (7=6)r8c5 => r8c5 = 6 ; stte

[Leren]

Code: Select all

*--------------------------------------------------------------*
| 257   3     257    | 6     4     9      | 28    1     258    |
| 8     6     25     | 3     1     7      | 4     9     25     |
| 1     9     4      |c28    5     28     | 3     7     6      |
|--------------------+--------------------+--------------------|
| 57    578   3      | 4     9     25     | 268   26    1      |
| 4     2     1      |c78   b67    68     | 9     5     3      |
| 9     8-5   6      |c25    3     1      | 7     4     28     |
|--------------------+--------------------+--------------------|
| 3     4     259    | 159   8     56     | 1256  26    7      |
| 2567 a57    8      | 17-5 a67    4      | 1256  3     9      |
| 567   1     579    | 579   2     3      | 56    8     4      |
*--------------------------------------------------------------*

ALS XY Wing: (5=6) r8c25 - (6=7) r5c5 - (7=5) r356c4 => - 5 r6c2, r8c4; stte

Leren

[pjb]

Leren:

An ALS XY Wing, or an XY chain of length 6?

Phil

[ronk]

Code: Select all

*--------------------------------------------------------------*
| 257   3     257    | 6     4     9      | 28    1     258    |
| 8     6     25     | 3     1     7      | 4     9     25     |
| 1     9     4      |c28    5     28     | 3     7     6      |
|--------------------+--------------------+--------------------|
| 57    578   3      | 4     9     25     | 268   26    1      |
| 4     2     1      |c78   b67    68     | 9     5     3      |
| 9     8-5   6      |c25    3     1      | 7     4     28     |
|--------------------+--------------------+--------------------|
| 3     4     259    | 159   8     56     | 1256  26    7      |
| 2567 a57    8      | 17-5 a67    4      | 1256  3     9      |
| 567   1     579    | 579   2     3      | 56    8     4      |
*--------------------------------------------------------------*

ALS XY Wing: (5=6) r8c25 - (6=7) r5c5 - (7=5) r356c4 => - 5 r6c2, r8c4; stte

An ALS XY Wing, or an XY chain of length 6?

It's an xy-chain expressed as an als-xy-wing.

[7b53]

It's an xy-chain expressed as an als-xy-wing.

so.. guess both Leren and pjb are right. depending how the notations are written.

[DonM]

This sort of confusion is exactly why the notation has to express what is going on.

Digressing for a minute:
The typical xy-chain uses bivalue cells.

In the rather unnecessarily complicated 'old' ALS terminology, a chain of 2 ALS sets is/was called an ALS xz-rule, a chain of 3 ALS sets is/was an ALS xy-wing and a chain of 4 sets or over is/was called an ALS xy-chain. (I pushed for years that we simply call all of them an ALS chain and that started to catch on, but now we're back to 2006...)

Still, no matter which way one looks at it, If one is notating a chain as an ALS XY-Wing, even if it acts similar to an XY-chain, then you still have to notate the digits of the set. Then there won't be any confusion:
(5=67) r8c25 - (6=7) r5c5 - (7=258) r356c4 => - 5 r6c2, r8c4; stte

[Marty R.]

Code: Select all

+--------------+-----------+-------------+
| 257  3   257 | 6   4  9  | 28   1  258 |
| 8    6   25  | 3   1  7  | 4    9  25  |
| 1    9   4   | 28  5  28 | 3    7  6   |
+--------------+-----------+-------------+
| 57   578 3   | 4   9  25 | 268  26 1   |
| 4    2   1   | 78  67 68 | 9    5  3   |
| 9    58  6   | 25  3  1  | 7    4  28  |
+--------------+-----------+-------------+
| 3    4   259 | 159 8  56 | 1256 26 7   |
| 2567 57  8   | 157 67 4  | 1256 3  9   |
| 567  1   579 | 579 2  3  | 56   8  4   |
+--------------+-----------+-------------+


Play this puzzle online at the Daily Sudoku site

XY-Chain

(5=7)r8c2-r8c5=r5c5-(7=8)r5c4-(8=2)r3c4-(2=5)r6c4=>r6c2<>5

[Marty R.]

Code: Select all

.----------------.-------------.---------------.
| 257   3    257 | 6    4   9  | 28    1   258 |
| 8     6    25  | 3    1   7  | 4     9   25  |
| 1     9    4   | 28   5   28 | 3     7   6   |
:----------------+-------------+---------------:
| f57   f578 3   | 4    9   e25| 268   26  1   |
| 4     2    1   | 78   b67 c68| 9     5   3   |
| 9     g58  6   | 25   3   1  | 7     4   28  |
:----------------+-------------+---------------:
| 3     4    259 | 159  8   d56| 1256  26  7   |
| 2567  h57   8  | 157 aI67 4  | 1256  3   9   |
| 567   1    579 | 579  2   3  | 56    8   4   |
'----------------'-------------'---------------'


(6)r8c5 = r5c5 - r5c6 = (6-5)r7c6 = (5)r4c6 - r4c12 = r6c2 - (5=7)r8c2 - (7=6)r8c5 => r8c5 = 6 ; stte

Steve,,

I'm missing something and not seeing how the last term is (7=6)r8c5. There's a 6 in r5c5 and a 7 in r8c2. Those would seem to trap r8c5, leaving it=1. Six is how r8c5 ends up, but I'm not seeing how the 1 got accounted for to allow the 7=6.

Thanks,
Marty

[ronk]

I'm missing something and not seeing how the last term is (7=6)r8c5. There's a 6 in r5c5 and a 7 in r8c2. Those would seem to trap r8c5, leaving it=1. Six is how r8c5 ends up, but I'm not seeing how the 1 got accounted for to allow the 7=6.

Perhaps it's an uppercase 'I'. Perhaps someone will expound on their personal preference not to use this letter.

[Luke]

This sort of confusion is exactly why the notation has to express what is going on.

I thought Danny Jones already put this one to bed!

Click

[pjb]

I felt that one went looking for ALSs when there wasn't a simple chain to be found which did the job. This means that at least one member of the ALS has to have more than 2 digits. If we all accept that its reasonable to use ALS notation as a way to abbreviate XY chains, then so be it.

Phil

[DonM]

This sort of confusion is exactly why the notation has to express what is going on.

I thought Danny Jones already put this one to bed!

Click

Yeah, I remember that thread now and my post was a shorter version of the one above. I remember not being sure whether Daj was serious or not- there was no smiley... From that thread, it appears that Leren came up with that notation on his own.

Hmm, does anyone know if Hodoku spits that out?

[daj95376]

This sort of confusion is exactly why the notation has to express what is going on.

I thought Danny Jones already put this one to bed!

Yeah, I remember that thread now and my post was a shorter version of the one above. I remember not being sure whether Daj was serious or not- there was no smiley... From that thread, it appears that Leren came up with that notation on his own.

Hmm, does anyone know if Hodoku spits that out?

I should have included a "smiley" in the referenced post -- maybe! The bastardization of the Eureka notation has become rampant. We need a way to condense "boring segments" without calling them ALS. However, I have no respect for bastardizing a reasonable solution so it can be called an "ALS XY-Wing".

HoDoKu uses Nice Loop notation and, any more, I have to reference my notes in order to recall how NL notation works.