The New Sudoku Players' Forum

[skjalg]

Since my previous post, I have read up on Unique Rectangles, but I am not sure if I have understood URT3 completely. I have a question, that has to do with Unqie Rectangle Type 3. Staring out with this puzzle:

Code: Select all

*---+---+---*
|...|...|...|
|...|841|...|
|.64|...|53.|
|---+---+---|
|..2|7.3|6..|
|7..|...|..5|
|.9.|.2.|.7.|
|---+---+---|
|..1|...|3..|
|.4.|.7.|.6.|
|9..|.8.|..7|
*---+---+---*


I get to the follwoing point using basic techniques:

Code: Select all

*------------------+--------------------+-------------------*
| 128   128   #79   | 56    3      56   | #14789 1489  1489 |
| 35    35    #79   | 8     4      1    | #279   29    6    |
| 18    6      4    | 2     9      7    |  5     3     18   |
|-------------------+-------------------+-------------------|
| 1458  158    2    | 7     15     3    |  6     1489  1489 |
| 7     138    368  | 469   16     4689 |  1248  1248  5    |
| 14568 9      568  | 456   2      458  |  148   7     3    |
|-------------------+-------------------+-------------------|
| 2568  7      1    | 4569  56     24569|  3     4589  2489 |
| 2358  4      358  | 13    7      259  |  189   6     1289 |
| 9     235    356  | 13    8      2456 |  14    145   7    |
*-------------------+-------------------+-------------------*


At this point I could use Unique Rectangle 4 to eliminate the 9s in r1c7 and r2c7.

Q) Am I correct in assuming that I could also remove <1,8> from r8c7 based on URT3 with naked quad?

Regards

_Skjalg

[wintder]

Yes.

R12 c7, because of the UR, are part of the quad that you noted.

[skjalg]

OK. Thanks for the confirmation.

[aran]

skjalg

Am I correct in assuming that I could also remove <1,8> from r8c7 based on URT3 with naked quad?

Or more simply, the elimination of the 9s in r12c7 automatically places 9 in r8c7, so eliminating <1,8>.