X-Chain question

Advanced methods and approaches for solving Sudoku puzzles

X-Chain question

Postby SpecialSauce » Tue Jul 02, 2019 3:51 am

X-Chain Hodoku Link: http://hodoku.sourceforge.net/en/tech_chains.php#x

My question is, if I find a chain of length 8, can I also try to make eliminations using smaller subsets of that chain of lengths 6 or 4? Or do I have to allow the chain to reach its natural end before I can make eliminations?

Thanks!
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Re: X-Chain question

Postby StrmCkr » Tue Aug 06, 2019 7:27 pm

eliminations can occur along shorter parts of the chain but only when the construct permits it.
Code: Select all
.----------.------------.---------------.
| 8   6  1 | 4  2    7  | 35     35  9  |
| 9   3  4 | 6  18   5  | 18     7   2  |
| 2   5  7 | 3  9    18 | 4      6   18 |
:----------+------------+---------------:
| 4   9  3 | 8  6    2  | 7      1   5  |
| 7   2  5 | 1  4    3  | 9      8   6  |
| 1   8  6 | 5  7    9  | 2      4   3  |
:----------+------------+---------------:
| 36  7  2 | 9  158  4  | 13568  35  18 |
| 36  1  9 | 7  58   68 | 3568   2   4  |
| 5   4  8 | 2  3    16 | 16     9   7  |
'----------'------------'---------------'


X-Chain: 1 r2c5 =1= r2c7 -1- r9c7 =1= r9c6 -1- r3c6 =1= r2c5 => r2c7,r3c6,r7c5<>1

X-Chain: 1 r2c5 =1= r2c7 -1- r9c7 =1= r9c6 => r3c6,r7c5<>1
Some do, some teach, the rest look it up.
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