999_Springs wrote:Is this classified as 3 strong links or bidirectional cycle or both or a type of fish with a long name?

Illustrating your example in the style of

The Ultimate FISH Guide ...

- Code: Select all
` / . . | / / X2| . . .`

/ . . | / / X | . . .

X * * | X2 X *X2| * * *

---------+---------+----------

/ . . | . . * | . . .

/ . . | . . * | . . .

/ . . | . . * | . . .

---------+---------+----------

X * * | . . * | . . .

X2 * * | . . * | . . .

/ X2 X | / / X | / / /

'X' <=> candidate in 999_Springs' illustration

"X2" <=> additional permissible candidate (as in 'X' too)

'/' <=> empty cell

'*' <=> elimination cell

'.' <=> candidate may or may not exist

As a fish (constraint sets): (unfinned) mutant swordfish r9c1b2\r3c6b7

Note that r3c6<>X is also true. See Fig 3E at the above link for a permuted rcb\rcb swordfish exemplar.

As a chain: multi-coloring, continuous loop, x-cycle, or bidirectional x-cycle

r7c1 =X= r3c1 -X- r3c5 =X= r2c6 -X- r9c6 =X= r9c3 -X- Loop (nice loop notation, assuming X2 cells are empty)

As a "grouped chain":

r78c1 =X= r3c1 -X- r3c456 =X= r2c456 -X- r9c6 =X= r9c23 -X- Loop (with X2 candidates)

[edits: 1) thanks to tarek for seeing typos; 2) added illustration and "grouped chain"]