The New Sudoku Players' Forum

[daj95376]

I'm learning to recognize Empty Rectangles. In the PM below, there seems to be two overlapping ERs in [r679]. I can use X-Colors -- in combination with Multi-Colors -- as an alternative to the ERs. What's the preferred technique to perform the eliminations in [r7c8] and [r9c3]?

Code: Select all

# ER 1 ???
 *-----------------------------------------------------------*
 | 4     8     359   | 23    6     1     | 579   279   39    |
 | 7     6     135   | 234   8     9     | 145   124   134   |
 | 19    39    2     | 347   57    35    | 8     6     1349  |
 |-------------------+-------------------+-------------------|
 | 6     49    8     | 5     2     7     | 149   3     149   |
 | 3     5     47    | 1     9     6     | 47    8     2     |
 | 2     1    *79    | 8     3     4     | 6    *79    5     |
 |-------------------+-------------------+-------------------|
 | 19    479   6     | 37    157   35    | 2    @149   8     |
 | 8     347   134   | 9     17    2     | 134   5     6     |
 | 5     2     13-9  | 6     4     8     |@139  @19    7     |
 *-----------------------------------------------------------*


Code: Select all

# ER 2 ???
 *-----------------------------------------------------------*
 | 4     8     359   | 23    6     1     | 579   279   39    |
 | 7     6     135   | 234   8     9     | 145   124   134   |
 | 19    39    2     | 347   57    35    | 8     6     1349  |
 |-------------------+-------------------+-------------------|
 | 6     49    8     | 5     2     7     | 149   3     149   |
 | 3     5     47    | 1     9     6     | 47    8     2     |
 | 2     1    *79    | 8     3     4     | 6    *79    5     |
 |-------------------+-------------------+-------------------|
 |@19   @479   6     | 37    157   35    | 2     14-9  8     |
 | 8     347   134   | 9     17    2     | 134   5     6     |
 | 5     2    @139   | 6     4     8     | 139   19    7     |
 *-----------------------------------------------------------*


Code: Select all

# X-Colors in combination with Multi-Colors
# B(lue) + G(reen)   and   P(ink) + A(mber)
# P+B and P+G => not P
 *-----------------------------------------------------------*
 | 4     8     359   | 23    6     1     | 579   279   39    |
 | 7     6     135   | 234   8     9     | 145   124   134   |
 | 19    39    2     | 347   57    35    | 8     6     1349  |
 |-------------------+-------------------+-------------------|
 | 6     49    8     | 5     2     7     | 149   3     149   |
 | 3     5     47    | 1     9     6     | 47    8     2     |
 | 2     1    B79    | 8     3     4     | 6    G79    5     |
 |-------------------+-------------------+-------------------|
 |A19   A479   6     | 37    157   35    | 2    P14-9  8     |
 | 8     347   134   | 9     17    2     | 134   5     6     |
 | 5     2    P13-9  | 6     4     8     |A139  A19    7     |
 *-----------------------------------------------------------*


[wapati]

What's the preferred technique to perform the eliminations in [r7c8] and [r9c3]?

ER wise you did fine.

Your ER-1 and ER-2 are easy finned X-wings for the same eliminations.

That would be my prefered method.

[daj95376]

What's the preferred technique to perform the eliminations in [r7c8] and [r9c3]?

ER wise you did fine.

Your ER-1 and ER-2 are easy finned X-wings for the same eliminations.

That would be my prefered method.

Aack! Thanks for making the obvious 'obvious' to me. I couldn't see the forest for the trees. ER 1 is a finned X-Wing, and ER 2 is a Sashimi X-Wing. They both exist at the same time ... and applying either one destroys the other. However, a secondary elimination follows through a Locked Candidate operation.

[wapati]

ER 1 is a finned X-Wing, and ER 2 is a Sashimi X-Wing. They both exist at the same time ... and applying either one destroys the other. However, a secondary elimination follows through a Locked Candidate operation.

My understanding is that you can apply them both at once.

You won't always notice both because one could create the other....
if both patterns are there you can apply them at the same time,
although they may trash one or the other.

Is this true? Anyone?? (We can see that it is true here, is it generally true??)