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I found turbot fish that could be 2 possible ways (IMHO), how could I detect which one is true?
I have used hodoku to detect the right one, but if not I still confused between these two possibilities..
In picture below (left is the answer, right is another possibility I have found)
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sudoku.png (61.58 KiB) Viewed 194 times
Danu Pr

Posts: 11
Joined: 16 February 2019

In the picture on the right, if this is supposed to be an AIC, the second arrow (row 1) must be a bi value. This is not correct here. The second arrow is not a strong inference.
champagne
2017 Supporter

Posts: 7163
Joined: 02 August 2007
Location: France Brittany

champagne wrote:In the picture on the right, if this is supposed to be an AIC, the second arrow (row 1) must be a bi value. This is not correct here. The second arrow is not a strong inference.

Ok, then how about the second arrow in the left,, is it a bi value? I see 3 of "7" in column 2,,
Danu Pr

Posts: 11
Joined: 16 February 2019

Actually they are both correct. Here is the solution. Both 7's have been eliminated.

Code: Select all
`*-----------------------*| 2 4 5 | 6 8 3 | 1 9 7 || 6 7 8 | 9 1 5 | 3 4 2 || 9 3 1 | 4 2 7 | 5 6 8 ||-------+-------+-------|| 4 9 7 | 1 3 2 | 6 8 5 || 1 2 6 | 5 9 8 | 7 3 4 || 5 8 3 | 7 6 4 | 2 1 9 ||-------+-------+-------|| 7 6 2 | 3 4 9 | 8 5 1 || 3 5 4 | 8 7 1 | 9 2 6 || 8 1 9 | 2 5 6 | 4 7 3 |*-----------------------*`

Why does Hodoku see one and not the other ? Well, it has to pick one first, and after that, only simpler moves are required to solve the puzzle. I tricked up my solver to eliminate the 7 in r9c2, but in a different way than you did.

Code: Select all
`*-------------------------------------------------------*| 27     4    35   | 6   38    358   | 1    b79   279   || 6     d27   8    | 9   13    135   |c2357  4   c257   || 9      13   135  | 4   2     7     | 358   6    58    ||------------------+-----------------+------------------|| 12345  9    7    | 138 1348  12348 | 256   18   12456 || 124    1268 146  | 5   9     1248  | 27    3    1247  || 12345  1238 134  | 7   6     12348 | 25    189  12459 ||------------------+-----------------+------------------|| 1347   1367 2    | 138 13478 9     | 678   5    1678  || 1347   5    1346 | 138 13478 1348  | 9     2    1678  || 8      1-7  9    | 2   5     6     | 4    a17   3     |*-------------------------------------------------------*`

I think you would have made your move clearer by just not putting the black arrow in Column 2 and making the arrow in Row 1 dotted. That way it would follow the same arrow convention as Hodoku does.

Leren
Leren

Posts: 3927
Joined: 03 June 2012

Leren wrote:Actually they are both correct. Here is the solution. Both 7's have been eliminated.

Code: Select all
`*-----------------------*| 2 4 5 | 6 8 3 | 1 9 7 || 6 7 8 | 9 1 5 | 3 4 2 || 9 3 1 | 4 2 7 | 5 6 8 ||-------+-------+-------|| 4 9 7 | 1 3 2 | 6 8 5 || 1 2 6 | 5 9 8 | 7 3 4 || 5 8 3 | 7 6 4 | 2 1 9 ||-------+-------+-------|| 7 6 2 | 3 4 9 | 8 5 1 || 3 5 4 | 8 7 1 | 9 2 6 || 8 1 9 | 2 5 6 | 4 7 3 |*-----------------------*`

Why does Hodoku see one and not the other ? Well, it has to pick one first, and after that, only simpler moves are required to solve the puzzle.

Leren

That was the correct answer I never expect. I should try to finish it first before.
Thanks,,,
Danu Pr

Posts: 11
Joined: 16 February 2019

Danu Pr wrote:
champagne wrote:In the picture on the right, if this is supposed to be an AIC, the second arrow (row 1) must be a bi value. This is not correct here. The second arrow is not a strong inference.

Ok, then how about the second arrow in the left,, is it a bi value? I see 3 of "7" in column 2,,

Sorry I answered too fast, the start is a clearly a "false" in the hodoku picture
champagne
2017 Supporter

Posts: 7163
Joined: 02 August 2007
Location: France Brittany

Like below
20200213080225.png (70.38 KiB) Viewed 165 times
yzfwsf

Posts: 247
Joined: 16 April 2019

Hi Danu Pr,

Actually both the Turbot Fish (i.e., Empty Rectangle) moves are correct, as pointed out by Leren and yzfwsf. It can also be detected by Hodoku by pressing "Find all steps" button present under "View" menu / "All Steps" option.

Also, please note that, both the 7's, i.e., from r1c8 and r9c2, may also be eliminated by single move, Dual Empty Rectangle, (with additional 7 elimination from r7c79 and r8c9) in Hodoku "Edit" menu / "Preferences" option / "Steps" tab, Tick mark on "Allow ERs with two candidates" and "Allow Duals/Siamese" in "Miscellaneous" section. However, the same effect may be obtained by just eliminating 7 from single cell from either r1c8 or r9c2, which then leads to the naked single placement of 7 in r9c8.

R. Jamil
Attachments
Dual Empty Rectangle: 7 in b1 (r19c8/r9c28) => r1c8,r9c2<>7
DualER.png (16.63 KiB) Viewed 155 times
rjamil

Posts: 596
Joined: 15 October 2014
Location: Karachi, Pakistan