Coloring question

whizter · Posted: Thu Jul 26, 2007 7:26 pm Post subject: Coloring question

I don't understand why 4 colors are needed in this multicolor-examples from sudopedia, if I just fill the cells with 2 colors, I come to the same result:

sudopedia. org/wiki/Multi-Colors

Can someone explain?

EDIT: Ok, I think I understood it now. A Unit must only contain 2 of the candidates to form the chain. This means that 2 chains are required because there are no connections between them. Is this true?

Ruud · Site Admin

In coloring, chains (or clusters, as I prefer to call them) can only be formed by conjugate pairs (2 candidates in a unit).

Multi-colors uses weak links between these chains. In techniques which depend on alternating inference, the pattern would be identified as a single chain.

Ruud

whizter · Posted: Fri Jul 27, 2007 10:24 am Post subject:

Thanks for the reply. I've got another question:

I know that it is required to scan for X-Wing 2 times, row-based and column-based. Is this also required for Swordfish and Jellyfish or is there always a complementary one which in the end results in the same eliminations? I know that there is always a complementary one, but are there setups where a row-based searching wouldn't result in eliminations, but a column-based would?

daj95376 · Posted: Fri Jul 27, 2007 2:06 pm Post subject:

I believe there is always a complementary fish, but there's no guarantee that it's of the same size. A Swordfish may have a Jellyfish (or larger) as the complementary fish.