swordfish?

Advanced methods and approaches for solving Sudoku puzzles

swordfish?

Postby nak » Thu Mar 08, 2007 11:04 pm

Hello,
I’m quite struggling spotting swordfish patterns
In this example http://img487.imageshack.us/img487/5837/sw1mm6.png i think there is a swordfish on 1.
The first swordfish is the one with the red lines, I assume that it’s a swordfish in rows. Can candidate 1 at position C be erased?
Then the blue lines, is there also a Swordfish? And if so then what is it, in rows or column.
If I consider it a swordfish in rows then candidate 1 at position A can not be eliminated, but if I consider it a swordfisch in columns then candidate 1 at position A can be eliminated.
Please can somebody help me with this.
gr Nak
nak
 
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Joined: 23 February 2007

Postby daj95376 » Thu Mar 08, 2007 11:52 pm

Your blue lines are correct for an elimination in A for <1>. However, you have incorrectly assigned [r2c2]=7 and this causes your red lines to be invalid. Next time, please post puzzles as text instead of graphics.

Code: Select all
# original puzzle
 *-----------*
 |...|479|62.|
 |..4|...|395|
 |926|...|...|
 |---+---+---|
 |.31|...|.69|
 |...|936|...|
 |..9|...|283|
 |---+---+---|
 |.5.|894|716|
 |4.8|...|952|
 |.97|.52|.3.|
 *-----------*

Code: Select all
# PM after SSTS but before Swordfish in c146/r269
 *-----------------------------------------------------------*
 | 35    18    35    | 4     7     9     | 6     2     18    |
 |*178  78-1   4     | 26    26   *18    | 3     9     5     |
 | 9     2     6     | 35    18    35    | 148   47    1478  |
 |-------------------+-------------------+-------------------|
 | 57    3     1     | 257   248   578   | 45    6     9     |
 | 258   48    25    | 9     3     6     | 145   47    147   |
 | 567   467   9     |*157   4-1  *157   | 2     8     3     |
 |-------------------+-------------------+-------------------|
 | 23    5     23    | 8     9     4     | 7     1     6     |
 | 4     16    8     | 37    16    37    | 9     5     2     |
 |*16    9     7     |*16    5     2     | 48    3     48    |
 *-----------------------------------------------------------*
daj95376
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