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[Marty R.]

Consider the following fragment: There is a skyscraper on 4 in rows 17 and a strong link in column 6. So one half of the skyscraper was colored AB and the other one CD. The 4 in r2c6 is colored A because of the strong link. Is the 4 in r2c8 a valid trap based on seeing both an A and D? If I correctly interpreted what I read in another thread, all color combinations are valid traps except AC, the colors in the weakly linked column.

[Asellus]

[Marty R.]

As always, thanks. You must realize by now that I have trouble with inferences, bridges, and the like. I have reached my skill level--whatever that level might be--by mechanical means. I don't see patterns and deduce very well. What I do is learn techniques and get them stated into "rule" form, then apply those rules to specific situations.

I obviously misunderstood/misinterpreted this statement in this thread:

"I simply note the colors in the margin: Eliminations can be made by red - green, blue - orange, AND by red - orange."

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2389

Again, thanks.

[keith]

[Marty R.]

[Asellus]

Marty,

There is nothing special about the particular colors. In Keith's example in the other thread, the weak link "bridge" between the two clusters happened to be green and blue. Green was conjugate with red, and blue was conjugate with orange. Therefore, the induced strong inference was between red and orange, the colors that were not involved in the weak link bridge of that example. However, in your example above, the weak link bridge is between A and C, or "red" and "blue", using Keith's assignments. So, in this case, the induced strong inference is between green and orange (B and D).

When he responded, Keith chose to assign colors to the ABDC letters you used above. Unfortunately, he didn't assign them in a way that matched his previous example. That is probably a good thing because it helps make it clear that there is nothing special about the colors one chooses. What is special is the links in the "bridges".

I hope that this bit of confusion ends up helping the concept make sense, because it really isn't that difficult. I am sure that you can see it, and that the "rules" will make sense to you.

[Marty R.]

[Asellus]

Marty,

The rules for Medusa multicoloring are really fairly simple. But first, we need to clear up some possible confusion.

When performing Medusa multicoloring, you must forget all about "extended" Medusa. The two things are very different. If you try to "extend" the color clusters when doing multicoloring, you will create too much complexity. You say you use "A" and "B" for your cluster, then you mention "a" and "b", so I assume those refer to the extensions of "A" and "B". So, let's be clear that Keith and I are not referring to such "extensions" in anything we've written above. The clusters we are talking about are strictly the conjugate clusters of basic Medusa.

When I recommended using A-a, B-b, C-c, etc., for marking the clusters, I did not mean to suggest using "extended" markings.

Let's turn to something louder than words:

[Marty R.]