The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |...|39.|71.|
 |...|...|8.3|
 |...|1.2|.9.|
 |---+---+---|
 |23.|8..|...|
 |..6|9.3|4..|
 |...|..6|.38|
 |---+---+---|
 |.1.|5.8|...|
 |3.4|...|...|
 |.57|.49|...|
 *-----------*


Play/Print this puzzle online

[SpAce]

All I found was horrible nets, while a simple answer was sitting right in front of me. Had to cheat to see it, so I'll sit this one out. I would have probably seen it more easily on paper, but it takes too much time to do daily puzzles like that

[SCLT]

A pretty chain with a group node at one end and an ALS at the other:

Code: Select all

*------------------------*-------------------*-----------------------*
|  46      246    8      |  3     9      5   |  7      1      246    |
|  159     29     1259   |  4     6      7   |  8     f25     3      |
|  4567    467    3      |  1     8      2   |  56     9      456    |
*------------------------+-------------------+-----------------------*
|  2       3      159    |  8     157    4   |  1569   567    569    |
| e1578   e78     6      |  9     1257   3   |  4     f257    25     |
| d14579  d479    159    | c27    1257   6   | b1259   3      8      |
*------------------------+-------------------+-----------------------*
|  69      1      29     |  5     3      8   | a269    4      7      |
|  3       2689   4      |  267   27     1   | a2569   2568   2569   |
|  68      5      7      |  26    4      9   |  3      68-2   1      |
*------------------------+-------------------+-----------------------*


2c7r78 = r6c7 - (2=7)r6c4 - r6c12 = r5c12 - (7=25)c8r25 => -2 r9c8 ; stte

[SpAce]

A pretty chain with a group node at one end and an ALS at the other:

Yep, it's pretty, and exactly the kind of chain I love to find. That's why I'm pissed I didn't see it. With my paper mark-up I probably would have, but I use Hodoku for quick solving and don't see those kinds of links as easily.

2c7r78 = r6c7 - (2=7)r6c4 - r6c12 = r5c12 - (7=25)c8r25 => -2 r9c8 ; stte

You could eliminate two with that AIC: -2 r89c8. Hodoku only reports one, though, because it uses a DNL instead of an AIC. Did you cheat too?

[SCLT]

You could eliminate two with that AIC: -2 r89c8. Hodoku only reports one, though, because it uses a DNL instead of an AIC. Did you cheat too?

Ah, well-spotted. I didn't cheat - this is a "lost in translation" elimination.

My solution as I originally found it was a Kraken cell starting from r6c4 which proved that r9c4 must be a 2. But since the starting cell is bivalue this can be trivially re-written as an AIC. Then I noticed that both halves of the chain went through 2r9c8 as a common link so I could shorten the final chain and change the result from a placement in r9c4 to an elimination in r9c8. I just didn't then look for further eliminations resulting from the now quite concise chain.

As an aside, I can't actually get my copy of Hodoku to find this chain (or anything similar) at all...

[SpAce]

Ah, well-spotted. I didn't cheat - this is a "lost in translation" elimination.

Great job! And sorry for the tongue-in-the-cheek question -- I was SO hoping that you'd cheated too!!!

As an aside, I can't actually get my copy of Hodoku to find this chain (or anything similar) at all...

You probably haven't turned on the "Allow ALS in chains" option (Preferences/Steps), which I think is off by default. I had the same problem until 200e200w advised me. After turning it on Hodoku started finding wonderful chains. It will find even more if you also check "Allow overlap" (in ALS general).

Btw, does anyone know what those "Only one chain per elimination" and "Only one step per elimination" options mean?

[Cenoman]

As a simple solution, grouped kite: (2)r9c4 = r9c8 - r78c7 = r6c7 => -2 r6c4: lclste
Too simple (?), so

Code: Select all

 +------------------------+--------------------+-----------------------+
 |  46      246    8      |  3     9      5    |  7      1      246    |
 |  159     29     1259   |  4     6      7    |  8      25#    3      |
 |  4567    467    3      |  1     8      2    |  56     9      456    |
 +------------------------+--------------------+-----------------------+
 |  2       3      159    |  8     157    4    |  1569   567#   569    |
 |  1578    78     6      |  9     1257   3    |  4      257#   25     |
 |  14579   479    159    |  27    1257   6    |  1259   3      8      |
 +------------------------+--------------------+-----------------------+
 |  69      1      29     |  5     3      8    |  269    4      7      |
 |  3       2689   4      |  267*  27#    1    |  2569   2568*  2569   |
 |  68      5      7      |  26*   4      9    |  3      268*   1      |
 +------------------------+--------------------+-----------------------+

UR(26)r89c48 using externals
(2)r25c8
(6-7)r4c8 = r4c5 - (7=2)r6c4 - r5c5 = r5c89 - r6c7 = (2)r78c7
(6-7)r4c8 = r4c5 - (7=2)r6c4 - r6c7 = (2)r78c7
(2)r8c5 - r5c5 = r5c89 - r6c7 = (2)r78c7
=> -2 r89c8; ste (-2 r9c8 alone gives ste finish)

EDIT: second chain shortened as suggested by SpAce

[SpAce]

As a simple solution, grouped kite: (2)r9c4 = r9c8 - r78c7 = r6c7 => -2 r6c4: lclste

UR(26)r89c48 using externals
(2)r25c8
(6-7)r4c8 = r4c5 - (7=2)r6c4 - r5c5 = r5c89 - r6c7 = (2)r78c7
(2)r8c5 - r5c5 = r5c89 - r6c7 = (2)r78c7
=> -2 r89c8; ste (-2 r9c8 alone gives ste finish)

Very nice, both of them! Btw, you could shorten the second UR chain a bit:

(6-7)r4c8 = r4c5 - (7=2)r6c4 - r6c7 = (2)r78c7

[Cenoman]

Btw, you could shorten the second UR chain a bit:

(6-7)r4c8 = r4c5 - (7=2)r6c4 - r6c7 = (2)r78c7

Yes, indeed !

[eleven]

Similar to SCLT's:

Code: Select all

 *-------------------------------------------------------------------*
 |  46      246    8      |  3     9      5  |  7      1      246    |
 |  159     29     1259   |  4     6      7  |  8      25     3      |
 |  4567    467    3      |  1     8      2  | a56     9      456    |
 |------------------------+------------------+-----------------------|
 |  2       3     d159    |  8    d157    4  | c1569   567   c569    |
 |  1578    78     6      |  9     1257   3  |  4      257    25     |
 |  14579   479    159    | e27    1257   6  | b1259   3      8      |
 |------------------------+------------------+-----------------------|
 |  69      1      29     |  5     3      8  | a269    4      7      |
 |  3       2689   4      |  267   27     1  | a2569   2568   2569   |
 |  68      5      7      |  26    4      9  |  3      268    1      |
 *-------------------------------------------------------------------*

2r78c7 = (2-1|9)r6c7 = hp19r4c79 - (1|9=57)r4c35 - (7=2)r6c4 - r6c7 = 2c7r78 => -2r6c7,r8c89,r9c8; stte
(the shorter version would only kill 2r6c7, and locked candidates would be left)

[pjb]

Code: Select all

 46      246     8      | 3      9      5      | 7      1      246   
 159     29      1259   | 4      6      7      | 8      25     3     
 4567    467     3      | 1      8      2      | 56     9      456   
------------------------+----------------------+---------------------
 2       3       159    | 8     b157    4      | 1569  c567    569   
 1578    78      6      | 9      157-2  3      | 4     d257   d25     
 14579   479     159    |a27     1257   6      | 159-2  3      8     
------------------------+----------------------+---------------------
 69      1       29     | 5      3      8      | 269    4      7     
 3       2689    4      | 267    27     1      | 2569   2568   2569   
 68      5       7      | 26     4      9      | 3      268    1     


Chain = (2=7)r6c4 - r4c5 = r4c8 - (7=25)r5c89 => -2 r5c5, r6c7; lclste

Phil