The New Sudoku Players' Forum

[Sudtyro]

Code: Select all

 +-----------------------------------+
 |  .  .  .  |  .  .  .  |  .  .  9  |
 |  9  .  .  |  .  9  .  |  .  .  .  |
 | -9  .  9  |  9 -9  9  |  .  .  .  |
 |-----------+-----------+-----------|
 |  .  9  .  |  .  .  .  |  .  .  .  |
 |  .  .  .  |  .  .  .  |  9  .  .  |
 |  .  .  .  |  9  .  9  |  .  .  .  |
 |-----------+-----------+-----------|
 | -9  .  9  |  9 -9  9  |  .  .  .  |
 |  9  .  .  |  .  9  .  |  .  9  .  |
 |  9  .  .  |  .  9  .  |  .  9  .  |
 +-----------------------------------+

How about an AIC loop:
(9): r3c3 = r7c3 – r7c46 = r789c5 – r23c5 = r3c46 – r3c3 => r37c15 <> 9.
That would seem to be a sort of mutant Swordfish using the b28 ERs,
maybe c3b28\r37c5?

[ronk]

One ER gets you nothing. Two ERs get you nothing. Three ERs get you one elimination.

All four eliminations can be made with a continuous loop of two ERs and one strong link. [edit: I see Sudtyro posted the same while I was typing.]

Code: Select all

 .  .  /  |  /  .  /  |  .  .  9
 9  .  /  |  / *9  /  |  .  .  .
-9  . *9  | *9 -9 *9  |  .  .  .
----------+-----------+----------
 .  9  /  |  .  .  .  |  .  .  .
 .  .  /  |  .  .  .  |  9  .  .
 .  .  /  |  9  .  9  |  .  .  .
----------+-----------+----------
-9  . *9  | *9 -9 *9  |  .  .  .
 9  .  /  |  / *9  /  |  .  9  .
 9  .  /  |  / *9  /  |  .  9  .

r3c3 =9= r7c3 -9- r7c456 =9= r789c5 -9- r23c5 =9= r3c456 -9- r3c3 =
A continuous loop implying r37c15<>9

Is this the ER technique? Of course not. I'm not making that claim and I didn't make such a claim earlier either.

I agree that one ER and one strong link is the classical example of an ER technique, but think saying it is the ER technique is misleading.

And I obviously agree there is a difference between an ER and ER technique. Your earliest post (to which I responded on this topic) described an ER as the combination of two strong inferences -- one each in a box and a row (or column) ... which it is not. Had you used the term ER technique there, I doubt I would have responded in the first place.

I doubt there is anything more I could say on this subject, so you may have the last word.

[daj95376]

Last Word:

An Empty Rectangle is a pattern that produces a constraint that is combined with other constraints to perform eliminations. Yes, an ER can be combined in many ways -- including with itself.

However, since none of these combinations have a name of their own, I think referring to Havard's original elimination example as an Empty Rectangle should be acceptable. When I produce an elimination this way, I include the row/column unit and the Empty Rectangle box to show specifically what I've done. That's why I said there was an Empty Rectangle in [r2b8].