The New Sudoku Players' Forum

[ronk]

This thread seems to have a mind of its own. First ronk posted a reply and then it disappeared. Then I added two more puzzles and ronk's message re-appeared.

Sorry about that. I originally illustrated a starfish (squirmbag) claiming both eliminations r2c47<>7 ... but it actually only supported r2c4<>7. Rather than just a quick edit, I thought I'd try again for both elims with one fish.

[ravel]

Code: Select all

+---+---+---+
|312|67.|.54|
|7..|4..|.36|
|.46|5..|..2|
+---+---+---+
|.71|3..|.68|
|.6.|2.7|..3|
|..3|.6.|...|
+---+---+---+
|...|.2.|.4.|
|1.7|8..|..5|
|.24|7.5|.81|
+---+---+---+


For my solution of the 38 after x-wing, W-wing and kite i need an x-chain to eliminate 9 in r2c5. It would be nice to have a fish for that (also the 9's in r2c7 and r3c1 can be eliminated with templates), because after that the puzzle can be solved with (swordfish and) xy-wing.

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  .  .  |  .  .  9  |
 |  .  9  .  |  .  9  9  |  9  9  .  |
 |  9  .  .  |  .  9  .  |  9  .  .  |
 *-----------------------------------*


[Edit:]What i can see is a jellyfish in rows 1, 3, 4 and 9 with fin in r3c8 to eliminate 2 in r2c7 and remote fin (?) for r2c5.

[daj95376]

ravel, There is a finned Jellyfish in r1492\c1567 with fin cells [r2c23]. This eliminates <9> in [r3c1] and leaves a Locked Candidate 1 to perform eliminations [r2c57]<>9.

BTW: Your fin cell [r3c8] is also an exo-fin cell that would force [r3c1]<>9 and the Locked Candidate 1 to eliminate <9> in [r2c5].

[ronk]

For my solution of the 38 after x-wing, W-wing and kite i need an x-chain to eliminate 9 in r2c5. It would be nice to have a fish for that (also the 9's in r2c7 and r3c1 can be eliminated with templates), because after that the puzzle can be solved with (swordfish and) xy-wing.

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  .  .  |  .  .  9  |
 |  .  9  .  |  .  9  9  |  9  9  .  |
 |  9  .  .  |  .  9  .  |  9  .  .  |
 *-----------------------------------*


After daj95376's offerings, it's nice to see an easy one again.

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  .  . |  .  .  9
 . *9  . |  .  9  9 |  9 *9  .
 9  .  . |  .  9  . |  9  .  .
 sashimi swordfish c238\r358 plus fin r2c23, implies r3c1<>9

... followed by locked candidates for r2c57<>9. I'm still looking for the W-wing. Again congratulations on your minimal 38

[udosuk]

I'm also puzzled about the w-wing. But I found a y-wing that together with an xy-wing solve the rest of the puzzle. Check out this post.

[ravel]

Thanks for your eplanations.

My "W-wing" is the same as udosuk's y-wing, indeed a semi-remote naked pair (is there another meaning of w-wing ?), see the discussion here.

[ronk]

Relative to the ravel.C38.m ...

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  .  . |  .  .  9
 . *9  . |  .  9  9 |  9 *9  .
 9  .  . |  .  9  . |  9  .  .
 sashimi swordfish c238\r358 plus fin r2c23, implies r3c1<>9

I discovered my solver doesn't find this sashimi, a basic fish. By "basic" I mean an unfinned, or finned, or sashimi row-column fish, IOW no frankens and no mutants.

The reason? Using the same base sectors (c238), there is also a finned swordfish -- c238\r258 plus fin r3c8. Once a finned fish is recognized, the solver doesn't bother to look for a sashimi that uses the same base sectors. I suspect my basic-fish-algorithm is not the only one with this design flaw.