The New Sudoku Players' Forum

[nedBlake]

Code: Select all

  *-----------*
  |.2.|7..|..3|
  |...|..5|7..|
  |3..|.98|...|
  |---+---+---|
  |...|87.|.5.|
  |..3|...|.6.|
  |.49|...|2..|
  |---+---+---|
  |...|2.9|.78|
  |..6|...|4..|
  |19.|...|...|
  *-----------*

[Cenoman]

The [quote]Extreme???[quote] in the subject should not be there (... the question marks).
nedBlake, you should know how extreme the puzzles you post are. A very simple mean to do that: process the puzzle in the software "Sudoku Explainer" No need to discuss how imperfect SE rating is. It is the tool commonly accepted, even in te community of hard puzzles searchers.

Your puzzle is rated SE 8.3 Not an easy one, but there exist harder ones.
Probably a rate much too high to fit the convention of this forum: proposed puzzles should be solved in one advanced step only. I don't know how Dan filter his puzzles, but his filters are very efficient.

The simplest path I have found to solve Extreme 9/9/17 is the five AIC's below:

Code: Select all

 Basics to 29
 +------------------------+-----------------------+------------------------+
 |  45689   2      1458   |  7     146     146    |  15689   1489   3      |
 |  4689    168    148    |  3     2       5      |  7       1489   169    |
 |  3       1567   1457   |  146   9       8      |  156     124    1256   |
 +------------------------+-----------------------+------------------------+
 |  26      16     12     |  8     7       34     |  39      5      49     |
 |  578     578    3      |  9     145     2      |  18      6      147    |
 |  578     4      9      |  156   1356    136    |  2       138    17     |
 +------------------------+-----------------------+------------------------+
 |  45      3      45     |  2     16      9      |  16      7      8      |
 |  278     78     6      |  15    1358    137    |  4       1239   1259   |
 |  1       9      278    |  456   34568   3467   |  356     23     256    |
 +------------------------+-----------------------+------------------------+
#1. (2)r8c1=r8c89-(2=3)r9c8-r6c8=(3-9)r4c7=(9-5)r1c7=r1c13-r3c2=r5c2-(5=2)r568c1 =>-2r4c1; basics to 33
#2. (3)r6c8=(3-9)r4c7=(9-8)r1c7=(8)r5c7 =>-8r6c8; basics to 38
 +--------------------+---------------------+-----------------------+
 |  459   2    1458   |  7     146   146    |  1569   1489   3      |
 |  49    68   148    |  3     2     5      |  7      1489   169    |
 |  3     67   1457   |  146   9     8      |  156    124    1256   |
 +--------------------+---------------------+-----------------------+
 |  6     1    2      |  8     7     34     |  39     5      49     |
 |  7     5    3      |  9     14    2      |  8      6      14     |
 |  8     4    9      |  156   35    136    |  2      13     7      |
 +--------------------+---------------------+-----------------------+
 |  45    3    45     |  2     16    9      |  16     7      8      |
 |  2     78   6      |  15    358   137    |  4      139    159    |
 |  1     9    78     |  456   358   3467   |  356    23     256    |
 +--------------------+---------------------+-----------------------+
#3. (6=1)r7c5-(1=5)r8c4-r8c9=(25-6)r39c9=r2c9-(6=8)r2c2-r12c3=(478)r9c346 =>-6r9c46; basics to 40
#4. (9)r8c8=r8c9-r4c9=(9-3)r4c7=(3)r9c7 =>-3r8c8; basics to 43
 +--------------------+-----------------+--------------------+
 |  459   2    458    |  7    14   16   |  569   48    3     |
 |  49    68   148    |  3    2    5    |  7     148   169   |
 |  3     67   1457   |  46   9    8    |  56    124   126   |
 +--------------------+-----------------+--------------------+
 |  6     1    2      |  8    7    34   |  39    5     49    |
 |  7     5    3      |  9    14   2    |  8     6     14    |
 |  8     4    9      |  56   35   16   |  2     13    7     |
 +--------------------+-----------------+--------------------+
 |  45    3    45     |  2    6    9    |  1     7     8     |
 |  2     78   6      |  1    38   37   |  4     9     5     |
 |  1     9    78     |  45   58   47   |  36    23    26    |
 +--------------------+-----------------+--------------------+
#5. (6=1)r1c6-r6c6=(1-3)r6c8=r9c8-(3=6)r9c7 =>-6r1c7; singles to 81

Not so extreme, after all. Have already seen worse.

To fit the forum's convention, I need the complex net path below:

Code: Select all

 +------------------------+-----------------------+------------------------+
 |  45689   2      1458   |  7     146     146    |  15689   1489   3      |
 |  4689    168    148    |  3     2       5      |  7       1489   169    |
 |  3       1567   1457   |  146   9       8      |  156     124    1256   |
 +------------------------+-----------------------+------------------------+
 |  26      16     12     |  8     7       34     |  39      5      49     |
 |  578     578    3      |  9     145     2      |  18      6      147    |
 |  578     4      9      |  156   1356    136    |  2       138    17     |
 +------------------------+-----------------------+------------------------+
 |  45      3      45     |  2     16      9      |  16      7      8      |
 |  278     78     6      |  15    1358    137    |  4       1239   1259   |
 |  1       9      278    |  456   34568   3467   |  356     23     256    |
 +------------------------+-----------------------+------------------------+
Multi-Kraken row (4)r3c348 => -4 r4c6; stte

              (3)r9c6-r8c56=(3-9)r8c8=r8c9-(9=4)r4c9-r5c9=(4)r5c5
             //                                                 \
(4-7)r3c3=r9c3-r9c6 =(4)r9c6-r4c6=(4)r5c5                       -(1)r5c5 =(4)r5c5                                                  -4r4c6
             \\                                                 /      \\
              (6)r9c6-(6=1)r7c5                                         (5)r5c5-r6c45=(5-8)r6c1=r6c8-r5c7=(8-9)r1c7=r4c7-(9=4)r4c9 -4r4c6

(4)r3c4-r9c4 =(438-5)r689c5=r5c5-r6c45=(5-8)r6c1=r6c8-r5c7=(8-9)r1c7=r4c7-(9=4)r4c9                                                -4r4c6
        \\
         (4)r9c6                                                                                                                   -4r4c6

(4-2)r3c8 =(2-9)r8c8=r8c9-r4c9=(9-3)r4c7=(3)r6c8-(3)r9c8 =(3)r6c8-r4c7=(3)r4c6                                                     -4r4c6
       \\                                       /       \\
        (2)r9c8                                          (3-9)r8c8=r8c9-(9=4)r4c9                                                  -4r4c6


A game just for once. Who will have the courage to read this hodgepodge of undigested links ?
Personnally I missed courage and motivation to tag the nodes in the diagrams.

Cenoman

[nedBlake]

First about the question marks that Cenoman objected to. He is right, in that my Grader recognized that it was an Extreme puzzle, but then gave up because there were strategies involved that it did not recognize, which inspired me to use the ?'s. But I did run the puzzle through Andrew Stuarts grader, which did indicate that the puzzle was difficult, but certainly not the most difficult. There were more strategy applications than I realized, which gave you a monumental task of documenting them in order to show how the puzzle could be solved.

I didn't realize that there were certain standards for puzzle submission. But I can see that a few number of Extreme strategy applications is desirable when submitting a puzzle at the Extreme level, and I will take this number more into consideration in the future.

I use the word "Extreme" to indicate the level of strategy required to solve a puzzle. For me Extreme indicates that the puzzle at least requires the ability to draw chains of such complexity that they could not be visualized otherwise (as opposed to Ywings for instance, which I would consider "Hard"). This information is useful to a user in deciding whether he wants to (or can) solve a puzzle. The number of stars following the strategy level then tells the user how long it will take him to solve the puzzle (the effort required).

[Leren]

I ran this puzzle through the Hodoku solver and, while it used many more moves than Cenoman, all the AIC's it used were linear.

So maybe this could be considered to be "simpler" then Cenoman's solution whilst not "shorter" (ie it involves more moves).

Hopefully this will not provoke a pointless discussion about the meaning of words like "simpler" and "shorter" etc.

Leren

PS The single candidate elimination stte list for this puzzle is non-empty : 9 r1c7, 9 r2c1, 4 r4c6, 3 r4c7, 9 r4c9 & 4 r5c9. I'm not even going to try to prove any of these.

Leren