The New Sudoku Players' Forum

[surbier]

Hi,

Inpired by discussion in the UR+2B/2SL thread,
I have implemented something like the an incomplete UR deadly pattern.
Where I complete an almost deadly pattern like

Code: Select all

   ab   abX

   abY  aZ


by the missing b, apply the zoo of UR methods and take b off again.
Endless loops by virtually inserting the 'missing' b into the
grid and eliminate the same b by one of the cannibalistic URs again and again are prevented.

Up to know I found only cases for the UR+3U/2SL, which looked rather suspiceous to me;
either my UR+3U/2SL code misses an elimation, or the UR+3U/2SL pattern provides
more elimations, than given by Mike Barker:

--- UR+3U/2SL: the strong links are disjoint with different labels => "a" can be removed from "abY"

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     ab-----abX
         a

         b
    abY-----abZ


I think there are more eliminations available:
Because of the symmetry of the UR+3U/2SL pattern (exchange of labels a and b)
b can be removed from "abY" as well.

[surbier]

What I said on the UR+3U/2SL is complete nonsense,
sorry for the noise

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+--------------------+--------------------+--------------------+
|   1     7  #25     |#235     6   23     |   9     4     8    |
|   6     3     9    |   7     8     4    | 15      2   15     |
| 45      8  #24-5   |#25      1     9    |   7     3     6    |
+--------------------+--------------------+--------------------+
| 479   49    48     | 138     5   37     |   6   18      2    |
| 57      6     1    | 28      4   27     |   3   58      9    |
|   3     2   58     | 18      9     6    |   4     7   15     |
+--------------------+--------------------+--------------------+
|   2     1     7    |   6     3     5    |   8     9     4    |
| 48    45      6    |   9     7   18     |   2   15      3    |
| 89    59      3    |   4     2   18     | 15      6     7    |
+--------------------+--------------------+--------------------+
UR+3U/2SL (25)[r1c3|r3c4] r3c3<>5
but 2 in r3c3 cannot be eliminated


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+--------------------+--------------------+--------------------+
                  -5-
|   1     7  #25     |#235     6   23     |   9     4     8    |
              |         |
              2         5
              |         |
|   6     3     9    |   7     8     4    | 15      2   15     |
| 45      8  #245    |#25      1     9    |   7     3     6    |
                  -2-
+--------------------+--------------------+--------------------+
| 479   49    48     | 138     5   37     |   6   18      2    |
| 57      6     1    | 28      4   27     |   3   58      9    |
|   3     2   58     | 18      9     6    |   4     7   15     |
+--------------------+--------------------+--------------------+
|   2     1     7    |   6     3     5    |   8     9     4    |
| 48    45      6    |   9     7   18     |   2   15      3    |
| 89    59      3    |   4     2   18     | 15      6     7    |
+--------------------+--------------------+--------------------+
            UR+3U/2SL (25)[r1c3|r3c4]  r3c3<>5
 incomplete UR+3U/2SL (25)[r1c3|r3c4]  r1c4<>2


The second elimination (after re-inserting 5 in 33) is
based on the rotated pattern using the other two strong links.

Nothing actually new

[daj95376]

Since two of your cells are bivalues <25>, I don't see your example as a UR+3U scenario.

--- UR+2D/1SL: cells with extra candidates diagonal to each other => strong link on "a" removes "a" from "abY" - repeat for each strong link

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 ab     abY
 |
 |a
 |
abX     ab


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 <25> UR+2D/1SL w/SL 5r1  =>  r3c3<>5
 <25> UR+2D/1SL w/SL 2r3  =>  r1c4<>2
 +-----------------------------------------------------+
 |  1    7   *25   | *235  6    23   |  9    4    8    | < SL:5
 |  6    3    9    |  7    8    4    |  15   2    15   |
 |  45   8   *245  | *25   1    9    |  7    3    6    | < SL:2
 |-----------------+-----------------+-----------------|
 |  479  49   48   |  138  5    37   |  6    18   2    |
 |  57   6    1    |  28   4    27   |  3    58   9    |
 |  3    2    58   |  18   9    6    |  4    7    15   |
 |-----------------+-----------------+-----------------|
 |  2    1    7    |  6    3    5    |  8    9    4    |
 |  48   45   6    |  9    7    18   |  2    15   3    |
 |  89   59   3    |  4    2    18   |  15   6    7    |
 +-----------------------------------------------------+
 # 33 eliminations remain


Using SLs 2c3 and 5r1 :

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 (2)r1c3 = (2-4)r3c3 =UR= (3-5)r1c4 = (5)r1c3 - loop  =>  r1c4<>2; r3c3<>5


[surbier]

Since two of your cells are bivalues <25>, I don't see your example as a UR+3U scenario.

Z is optional, It's a UR+3U with Z being {}

UR+2D/1SL: cells with extra candidates diagonal to each other => strong link on "a" removes "a" from "abY" - repeat for each strong link

I fully agree

[ronk]

Since two of your cells are bivalues <25>, I don't see your example as a UR+3U scenario.

Z is optional, It's a UR+3U with Z being {}

Sorry, but I think the "optional" concept is a bad one. An AUR, and UR for that matter, either has "extra candidates" in one, two, three or all four cells. That's the primary classification property in Mike Barker's name assignments.

[daj95376]

I didn't like the optional reply either, but I didn't say so because it leaves open for discussion the concept of optional UR values in the UR cells -- as in Myth Jellies' (?) UR Type 1.1 . In Mike Barker's scenarios, "ab" is present in all four UR cells.

[ronk]

I didn't like the optional reply either, but I didn't say so because it leaves open for discussion the concept of optional UR values in the UR cells -- as in Myth Jellies' (?) UR Type 1.1 . In Mike Barker's scenarios, "ab" is present in all four UR cells.

The UR1.1 and it's brethren have been around a while. Does anyone now use the "optional" term in that context?

[surbier]

Z is optional, It's a UR+3U with Z being {}

I will not defend this.

My understanding is, that the zoo of URs is complete in coverage.
In so far it is not necessary to consider the labels for the additional
candidates as optional. Nevertheless, when coding, I allowed for the
'optional' since I was curious. It was not intended to compensate for
missed URs like the UR+2D/2SL which I implemented later and forgot
to activate.