The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |.4.|217|...|
 |8..|.5.|...|
 |.2.|8.6|...|
 |---+---+---|
 |3.2|...|1.4|
 |78.|...|.39|
 |4.6|...|8.2|
 |---+---+---|
 |...|9.3|...|
 |...|.4.|6.3|
 |...|182|.5.|
 *-----------*


Play/Print this puzzle online

[pjb]

Code: Select all

 59-6    4       359    | 2      1      7      | 39    a89    a68     
 8       36      37     | 4      5      9      | 237    12     16     
 1       2       79     | 8      3      6      | 479    49     5     
------------------------+----------------------+---------------------
 3       9       2      | 5      7      8      | 1      6      4     
 7       8       1      | 6      2      4      | 5      3      9     
 4       5       6      | 3      9      1      | 8      7      2     
------------------------+----------------------+---------------------
 25      7       458    | 9      6      3      | 24     1248   18     
 29      1       89     | 7      4      5      | 6     b289    3     
d69      36      349    | 1      8      2      |c49     5      7     


(6=9)r1c89 - r8c8 = r9c7 - (9=6)r9c1 => -6 r1c1; stte

Phil

[Leren]

Code: Select all

*---------------------------------------------------------------*
| 569   4     359    | 2     1     7      | 39   a89     6-8    |
| 8    f36    37     | 4     5     9      | 237   12    g16     |
| 1     2     79     | 8     3     6      | 479   49     5      |
|--------------------+--------------------+---------------------|
| 3     9     2      | 5     7     8      | 1     6      4      |
| 7     8     1      | 6     2     4      | 5     3      9      |
| 4     5     6      | 3     9     1      | 8     7      2      |
|--------------------+--------------------+---------------------|
|d25    7     458    | 9     6     3      | 24    124-8 h18     |
| 29    1     89     | 7     4     5      | 6    b29-8   3      |
|d69   e36    349    | 1     8     2      |c49    5      7      |
*---------------------------------------------------------------*

(8=9) r1c8 - r8c8 = r9c7 - (9=6) r9c1 - r9c2 = r2c2 - (6=1) r2c9 - (1=8) r7c9 => - 8 r1c9, r78c8; stte

Leren

[SteveG48]

Code: Select all

 *------------------------------------------------------------*
 |a569   4   ab359   | 2     1     7     |ab39    8-9   68    |
 | 8     36    37    | 4     5     9     |  237   12    16    |
 | 1     2    b79    | 8     3     6     |  479   49    5     |
 *-------------------+-------------------+--------------------|
 | 3     9     2     | 5     7     8     |  1     6     4     |
 | 7     8     1     | 6     2     4     |  5     3     9     |
 | 4     5     6     | 3     9     1     |  8     7     2     |
 *-------------------+-------------------+--------------------|
 | 25    7    c458   | 9     6     3     | d24    1248  18    |
 | 29    1    c89    | 7     4     5     |  6    d289   3     |
 | 69    36    349   | 1     8     2     |  49    5     7     |
 *------------------------------------------------------------*


Just for fun, I think this parses correctly and works in either direction:

9r1c137 = ((3&5)r1c37)&(9r3c3) - (5|9=4&8)r78c3 - (4|8=2&9)b9p15 => -9 r1c8 ; stte

[Marty R.]

Code: Select all

+------------+-------+-------------+
| 569 4  359 | 2 1 7 | 39  89   68 |
| 8   36 37  | 4 5 9 | 237 12   16 |
| 1   2  79  | 8 3 6 | 479 49   5  |
+------------+-------+-------------+
| 3   9  2   | 5 7 8 | 1   6    4  |
| 7   8  1   | 6 2 4 | 5   3    9  |
| 4   5  6   | 3 9 1 | 8   7    2  |
+------------+-------+-------------+
| 25  7  458 | 9 6 3 | 24  1248 18 |
| 29  1  89  | 7 4 5 | 6   289  3  |
| 69  36 349 | 1 8 2 | 49  5    7  |
+------------+-------+-------------+


Play this puzzle online at the Daily Sudoku site

Same elimination, less parsing.

M-Wing (49); (9=4)r3c8-r7c8=(4-9)r9c7=r13c7=> -9r1c8

[SteveG48]

Code: Select all

+------------+-------+-------------+
| 569 4  359 | 2 1 7 | 39  89   68 |
| 8   36 37  | 4 5 9 | 237 12   16 |
| 1   2  79  | 8 3 6 | 479 49   5  |
+------------+-------+-------------+
| 3   9  2   | 5 7 8 | 1   6    4  |
| 7   8  1   | 6 2 4 | 5   3    9  |
| 4   5  6   | 3 9 1 | 8   7    2  |
+------------+-------+-------------+
| 25  7  458 | 9 6 3 | 24  1248 18 |
| 29  1  89  | 7 4 5 | 6   289  3  |
| 69  36 349 | 1 8 2 | 49  5    7  |
+------------+-------+-------------+


Play this puzzle online at the Daily Sudoku site

Same elimination, less parsing.

M-Wing (49); (9=4)r3c8-r7c8=(4-9)r9c7=r13c7=> -9r1c8

Ah, but is it as much fun?

Well done.

[Leren]

Marty R wrote ; M-Wing (49); (9=4)r3c8-r7c8=(4-9)r9c7=r13c7=> -9r1c8

Sorry Marty, the indicated Strong link doesn't work because there are three 4's in Box 9, the third one in r7c7, so no M-Wing there.

Leren

[Marty R.]

Marty R wrote ; M-Wing (49); (9=4)r3c8-r7c8=(4-9)r9c7=r13c7=> -9r1c8

Sorry Marty, the indicated Strong link doesn't work because there are three 4's in Box 9, the third one in r7c7, so no M-Wing there.

Leren

OK, thanks.

[Marty R.]

Code: Select all

+------------+-------+-------------+
| 569 4  359 | 2 1 7 | 39  89   68 |
| 8   36 37  | 4 5 9 | 237 12   16 |
| 1   2  79  | 8 3 6 | 479 49   5  |
+------------+-------+-------------+
| 3   9  2   | 5 7 8 | 1   6    4  |
| 7   8  1   | 6 2 4 | 5   3    9  |
| 4   5  6   | 3 9 1 | 8   7    2  |
+------------+-------+-------------+
| 25  7  458 | 9 6 3 | 24  1248 18 |
| 29  1  89  | 7 4 5 | 6   289  3  |
| 69  36 349 | 1 8 2 | 49  5    7  |
+------------+-------+-------------+


Play this puzzle online at the Daily Sudoku site

Let's try this again.

Kraken, 9s in c7.
9r1c7=9r3c7=9r9c7
9r13c7-(9=8)r1c8
9r9c7-(9=6)r9c1-(6=3598)r1c1378=> 8r1c8

OK, my first Kraken. With no offense to anyone. I've been told that Kraken has been used this way on this forum.
It feels like a trial-and-error triple implication chain. Give it a fancy name like Kraken, that's lipstick on a pig.

[SteveG48]

Code: Select all

+------------+-------+-------------+
| 569 4  359 | 2 1 7 | 39  89   68 |
| 8   36 37  | 4 5 9 | 237 12   16 |
| 1   2  79  | 8 3 6 | 479 49   5  |
+------------+-------+-------------+
| 3   9  2   | 5 7 8 | 1   6    4  |
| 7   8  1   | 6 2 4 | 5   3    9  |
| 4   5  6   | 3 9 1 | 8   7    2  |
+------------+-------+-------------+
| 25  7  458 | 9 6 3 | 24  1248 18 |
| 29  1  89  | 7 4 5 | 6   289  3  |
| 69  36 349 | 1 8 2 | 49  5    7  |
+------------+-------+-------------+


Play this puzzle online at the Daily Sudoku site

Let's try this again.

Kraken, 9s in c7.
9r1c7=9r3c7=9r9c7
9r13c7-(9=8)r1c8
9r9c7-(9=6)r9c1-(6=3598)r1c1378=> 8r1c8

OK, my first Kraken. With no offense to anyone. I've been told that Kraken has been used this way on this forum.
It feels like a trial-and-error triple implication chain. Give it a fancy name like Kraken, that's lipstick on a pig.

Hi, Marty. No offense taken, , but I don't see why you would think of this as a trial and error solution. You've demonstrated that whichever candidate 9 in column 7 is true it leads to the conclusion that r1c8 must be 8. That seems perfectly logical to me.

Let's note that your Kraken solution can be pretty easily written as a simple chain:

(9=356)r1c137 - (6=9)r9c1 - r9c7 = 9r13c7 => -9 r1c8

However, most often when I see Kraken solutions posted here, it's done to avoid writing a chain with multiple branches. Instead, separate chains are written starting at the branch point to demonstrate the desired result. It's generally a network solution, but I don't see it as trial and error.

[Marty R.]

whichever candidate 9 in column 7 is true it leads to the conclusion that r1c8 must be 8. That seems perfectly logical to me.

Steve, that's exactly the argument I made way back then against those experienced players who said Forcing Chains were trial and error. Things I learned early on stick with me, as if they were "imprinted." This Kraken looks like a Forcing Chain with three possibilities, a fishing expedition. This'll probably never be one of my favorites, but I'll continue to use it where necessary because every one else here uses it.

[DonM]

whichever candidate 9 in column 7 is true it leads to the conclusion that r1c8 must be 8. That seems perfectly logical to me.

Steve, that's exactly the argument I made way back then against those experienced players who said Forcing Chains were trial and error. Things I learned early on stick with me, as if they were "imprinted." This Kraken looks like a Forcing Chain with three possibilities, a fishing expedition. This'll probably never be one of my favorites, but I'll continue to use it where necessary because every one else here uses it.

The term, forcing chain, is a broad term. The Forcing Chain 'method' where you basically assume a value and see what happens is pure trial and error. That said, any Kraken method is more 'assumptive' than a basic chain. Back in the day, the idea was to solve with as little assumptivety as possible. On this forum, the aim has become to solve with a single chain regardless of anything to do with assumptivety...

[eleven]

Let's note that your Kraken solution can be pretty easily written as a simple chain:

(9=356)r1c137 - (6=9)r9c1 - r9c7 = 9r13c7 => -9 r1c8

Yes, however nearly no one would spot it that way.
Instead most manual solvers would accidentally find it, e.g. when looking for a common implication of 8 and 9 in r1c8 (clean method, not seen as t&e), and noticing that 9r1c8 implies 8r1c8, which is a contradiction (Ugh!)

@newbies: if you find a contradiction elimination, better reformulate it on this forum, to avoid any bashing.