dailysudoku.com

[farfel]

Does this logic have a name ? On the Sept 3 sudoku I got stuck and then noticed a relationship among 4 pairs that looked like this:

26---25


68---58


Starting with the 26 pair, the 25 becomes a 5, the 58 an 8 and the 68 a 6, which gives:

2---5
6---8

Doing the same with all the top row numbers, there are only 2 possibilities:

2---5 and
6---8

6---2
8---5


From this, I deduced that I could eliminate all the 2s from the top row, all the 5s from the right column, all the 8s from the bottom row and all the 6s from the left column.

Does this logic have a name?

[ravel]

Sudoku susser calls it "forcing loop", Sudoku Explainer "bidirectional y-cycle". I cant find a good online description now. See here for another sample.

[farfel]

Thanks. And I thought I discovered something new....I'd call it the "Farfel chain"

[Steve R]

A nice observation, Farfel. Welcome to the forum!

You may find Scanraid’s description of xy-chains helpful. When the chain comes back to the starting cell it sometimes forms an xy-ring.

[Marty R.]

Despite all the descriptive terms like loops, cycles, rings, etc., are these also a form of forcing chain or double implication chain? After all, in each example, we are testing a 26 cell for each value, and for each of those values the same action is taken.

[TexCat]

I thought this was an interesting technique. I was sure it would be called some fishy name, and in my mind had already renamed farfel fish.

[farfel]

Thanks TexCat. I'll do anything for my 15 minutes of fame