(*) cell eliminations for Locked Pair
+-----------------------------------+
| 12 12 * | * * * | * * * |
| * * * | . . . | . . . |
| * * * | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-----------------------------------+
rick.schneider wrote:Thanks, daj. I think I have been asking myself the wrong question.
In the following table, how can I tell which cells are part of the swordfish, and which can be eliminated. If I eliminate the small n's, it doesn't work, and I don't know why. Thanks for the help.
N n N
n N N
N N
+-----------------------------------+
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| / X / | X / / | / / X |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
+-----------------------------------+
+-----------------------------------+
| . * . | * . . | . . * |
| / X / | X / / | / / X |
| . * . | * . . | . . * |
|-----------+-----------+-----------|
| / X / | X / / | / / X |
| . * . | * . . | . . * |
| . * . | * . . | . . * |
|-----------+-----------+-----------|
| . * . | * . . | . . * |
| / X / | X / / | / / X |
| . * . | * . . | . . * |
+-----------------------------------+
hobiwan wrote:If your swordfish looks like this:
- Code: Select all
+-----------------------------------+
| . . . | . . . | . . . |
| . X . | X . . | . . X |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . X . | X . . | . . X |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| . X . | X . . | . . X |
| . . . | . . . | . . . |
+-----------------------------------+
it is a "swordfish in the rows". Rows 2, 4 and 8 are called the "base set". Since the candidates in those rows are in columns 2, 4 and 9, those columns are called the "cover set" and you can eliminate all candidates in the cover set, that are not part of the base set
+-----------------------------------+
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| / X / | X / / | / / X |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
+-----------------------------------+
Pat wrote:a correction to hobiwan's post --the diagram as shown
from hobiwan's text, his diagram should've been --
could be a Swordfish in rows
and could be a Swordfish in columnsa Swordfish is not determined by the cells where the digit can be,
it is determined by the cells where the digit cannot be
- Code: Select all
+-----------------------------------+
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| / X / | X / / | / / X |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|-----------+-----------+-----------|
| . . . | . . . | . . . |
| / X / | X / / | / / X |
| . . . | . . . | . . . |
+-----------------------------------+
-- as he said, exclude the digit in columns 2,4,9 outside of rows 2,4,8