The New Sudoku Players' Forum

[tarek]

Code: Select all

+-------+-------+-------+
| . 1 5 | 7 . . | 6 . . |
| . 8 . | . 4 1 | . 2 . |
| 2 . . | . . . | . . . |
+-------+-------+-------+
| . 2 . | . . . | 4 . . |
| . . 3 | 1 . 7 | 8 . . |
| . . 7 | . . . | . 5 . |
+-------+-------+-------+
| . . . | . . . | . . 3 |
| . 3 . | 5 7 . | . 8 . |
| . . 9 | . . 6 | 5 4 . |
+-------+-------+-------+


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[Leren]

Code: Select all

*----------------------------------------------*
| 3    1 5   | 7    28   28    | 6    9   4    |
| 7    8 6   | 9    4    1     | 3    2   5    |
| 2    9 4   | 36   356  35    | 17   17  8    |
|------------+-----------------+---------------|
| 1589 2 18  | 68   5689 589   | 4    3   7    |
| 59   4 3   | 1    259  7     | 8    6   29   |
|a89   6 7   | 2348 2389 23489 | 12   5  d12-9 |
|------------+-----------------+---------------|
| 6    5 128 | 248  1289 2489  | 1279 17  3    |
| 4    3 12  | 5    7    29    | 129  8   6    |
|b18   7 9   | 238  1238 6     | 5    4  c12   |
*----------------------------------------------*

H3 Wing: (9=8) r6c1 - (8=1) r9c1 - r9c9 = (1) r6c9 => - 9 r6c9; stte

Leren

[SteveG48]

Code: Select all

 *--------------------------------------------------------------------*
 | 3      1      5      | 7     b28    c28     | 6      9      4      |
 | 7      8      6      | 9      4      1      | 3      2      5      |
 | 2      9      4      | 36     356   d35     | 17     17     8      |
 *----------------------+----------------------+----------------------|
 | 159-8  2      1-8    |a68    a5689 ad589    | 4      3      7      |
 | 59     4      3      | 1     a259    7      | 8      6      29     |
 | 89     6      7      | 234-8  239-8  2349-8 | 12     5      129    |
 *----------------------+----------------------+----------------------|
 | 6      5      128    | 248    1289   2489   | 1279   17     3      |
 | 4      3      12     | 5      7     d29     | 129    8      6      |
 | 18     7      9      | 238    1238   6      | 5      4      12     |
 *--------------------------------------------------------------------*


I'm curious what the group thinks of this notation, in which the required 8 at the right end of
the chain appears in either the penultimate term or the final term:

(8=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2=8|3)r348c6 - (3=68)r34c4 => -8 r4c13,r6c456 ; stte

I can avoid the difficulty using a starred memory chain:

(8*=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2*8=593)r348c6 - (3=68)r34c4 => -8 r4c13,r6c456 ; stte

Or we can build memory into the chain and get a pure but more complex AIC:

(8=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2=8|3)r348c6 - 3r3c4&8r167c6 = (68)r34c4|8r4c6 => -8 r4c13,r6c456 ; stte

Thoughts? (So where is SpAce anyway?)

[Cenoman]

Code: Select all

 +--------------------+------------------------+--------------------+
 |  3      1    5     |  7     c28     28      |  6      9    4     |
 |  7      8    6     |  9      4      1       |  3      2    5     |
 |  2      9    4     |  36     356    35      |  17     17   8     |
 +--------------------+------------------------+--------------------+
 | a1589   2   k18*   |  6-8*  a5689  a589     |  4      3    7     |
 |  59     4    3     |  1     d259    7       |  8      6    29    |
 |  89     6    7     |ea2348  d2389  e23489   | f12     5   g129   |
 +--------------------+------------------------+--------------------+
 |  6      5   j128*  | a248    1289   2489    |  1279   17   3     |
 |  4      3    12    |  5      7      29      |  129    8    6     |
 | i18*    7    9     |  238*  b1238   6       |  5      4   h12    |
 +--------------------+------------------------+--------------------+

5-link oddagon (8)r49, c34, b7 with 6 guardians:
(8)r4c156,r67c4 == (8)r9c5 - (8=2)r1c5 - r56c5 = r6c46 - (2=1)r6c7 - r6c9 = r9c9 - (1=8)r9c1 - r7c3 = (8)r4c3 => -8r4c4; ste

[SpAce]

Hi Steve,

Thoughts? (So where is SpAce anyway?)

What, are you really missing my pain-in-the-butt input? I'm honored! Well, since there seems to be no other takers for your good question (and I just happened to notice it), here goes nothing...

First of all, nice solution! I can see why you found it a bit tricky to notate.

(8=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2=8|3)r348c6 - (3=68)r34c4 => -8 r4c13,r6c456 ; stte

I can avoid the difficulty using a starred memory chain:

(8*=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2*8=593)r348c6 - (3=68)r34c4 => -8 r4c13,r6c456 ; stte

To be honest, I can't quite see how the latter chain is supposed to work. I think the only memory you really need is for the alternate end point, and for that the first version was closer. Just add a star to the (8*|3) node and link it to the eliminations! It's a bit ugly, though:

(8=5692)b5p1235 - r1c5 = (29)r18c6 - (95=8*|3)r43c6 - (3=68)r34c4 => -(*)8 r4c13,r6c456

(Never mind my alternate beginning.) Personally I've used '@' as a special marker for alternate (and extra) end points to avoid starring the eliminations, but it's probably not understood by all (and I'm not sure which side of the 8 it's better):

(8=5692)b5p1235 - r1c5 = (29)r18c6 - (95=8@|3)r43c6 - (3=68)r34c4 => -8 r4c13,r6c456

Or we can build memory into the chain and get a pure but more complex AIC:

(8=5692)b5p1235 - (2=8)r1c5 - (8=2)r1c6 - (2=8|3)r348c6 - 3r3c4&8r167c6 = (68)r34c4|8r4c6 => -8 r4c13,r6c456 ; stte

I have no objection to that, except for what you said about the complexity. It's pretty much impossible to avoid in these situations. All you can do is transform it into a different kind of complexity. Here's one way to write it with a bit less apparent complexity, but the price is a multi-house node of which I'm not a fan:

(8=5692)b5p1235 - r1c5 = (29)r18c6 - (95)r43c6 = (8)r4c6|(368)r3c64,r4c4 => -8 r4c13,r6c456

Would any of these options work for you?

[SteveG48]

Hello, SpAce. Thanks. I'm glad you responded. Yes, I miss your posts. As you observed, no one else seems as interested in nuances of notation as you and I are.

The options you provide are good. I love pure, bi-directional AICs, and the more I think about it, the more the notation I used seems like just another form of starred memory notation, as you pointed out. Going forward, I'll accept either the complexity of the AIC or accept the stars, depending on my mood at the time. I can't pretend that the form I used is "purer" than other memory chains.

[SpAce]

Hello, SpAce. Thanks. I'm glad you responded. Yes, I miss your posts. As you observed, no one else seems as interested in nuances of notation as you and I are.

Thanks Steve, I'm glad to hear that! I'm also happy that you share the rare passion for notational nuances I miss being around too, though I also think it's been a good idea to take a little break.

Going forward, I'll accept either the complexity of the AIC or accept the stars, depending on my mood at the time. I can't pretend that the form I used is "purer" than other memory chains.

I hear you. I've also tried to shed any form of purism if it doesn't serve a practical purpose. Writing complex AICs is a fun challenge, but they're not always the best ways to communicate complex pieces of logic, even if one is skillful enough to write them correctly. Writing them is typically more fun than reading them. When branching is required, krakens, net diagrams, and matrices are usually the best options for maximum clarity, and they're also easier to write correctly. Of course for people like you and me they're a bit boring for the same reasons

Sometimes a memory chain is the most natural fit, and I don't have any aversion to using or seeing them either. However, I think their niche is limited to relatively simple cases when an AIC would be awkward and a net diagram an overkill. (Besides, a badly formed memory chain is really bad, and those are not rare. For that reason I'd recommend sticking to explicit branching with krakens and net diagrams for most people.)