## Chain Notation

Advanced methods and approaches for solving Sudoku puzzles

### Chain Notation

Code: Select all
`+----------------+--------------------+-----------------+| 1      6(5)  3 | 8     9      7     | 4      2   6(5) || 2(5)   7     8 | 4     23(5)  6     | 9(5)   39  1    || 9      256   4 | 1     235    25    | 8      7   356  |+----------------+--------------------+-----------------+| 28(5)  4     6 | 2(5)  7      9     | 1      38  3(5) || 3      2(5)  7 | 6     1      28(5) | 29(5)  89  4    || 258    1     9 | 3     8-5    4     | 25     6   7    |+----------------+--------------------+-----------------+| 6      9     2 | 7     4      1     | 3      5   8    || 4      8     5 | 9     6      3     | 7      1   2    || 7      3     1 | 25    258    258   | 6      4   9    |+----------------+--------------------+-----------------+`

In my Subsets thread Pjb recently wrote:
If you have trouble with jellyfish as I do, then a series of simple AICs will suffice (some of them skyscrapers):
1.Chain: (2)r2c5 = r2c1 - r4c1 = r4c4 => -2 r6c5
2.Chain: (5=2)r3c6 - r5c6 = r4c4 - (2=5)r9c4 => -5 r9c6
3.Chain: (5=9)r2c7 - r2c8 = (9-8)r5c8 = r5c6 - (8=5)r6c5 => -5 r2c5, r6c7
4.Line/Box: 5s at r3c56 => -5 r3c29
5.Chain: (2=5)r2c1 - (5=9)r2c7 - (9=5)r5c7 - (5=2)r5c2 => -2 r3c2, r4c1 => stte

I can follow the logic, with some difficulty, but I just don't know the intended meaning of a lot of these terms.
I would tend to describe Chain1 with a series of logic steps, something like:
r2c5<>2 => 2r2c1 => r4c1<>2 => 2r4c4 => r6c5<>2
OR 2r2c5 => r6c5<>2 Delete 2 as candidate from r6c5.
Hodoku says my prefered notation tends to be used in forcing chains, while this type above is more for AICs, but are they all that distinct?
Is there a thread which explains the standard notations for Chains used in this forum?
Yogi
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Location: New Zealand

### Re: Chain Notation

The notation convention most commonly used on this forum is Eureka notation.

A reasonably compact description can be found on the Sudopedia site here.

Leren
Leren

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Joined: 03 June 2012

### Re: Chain Notation

The crucial point is that the second set of chains you mentioned are directional, if-then, relationship while the first set are symmetrical, i.e. they supports reasoning in both directions.

JasonLion
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