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 Post subject: Help with this puzzle
PostPosted: Wed Jun 17, 2009 8:26 pm 
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This puzzle is advertised to need nothing more difficult than a swordfish (which I've already found), but I can't get further than this, and JSudoku says it can't be solved without enabling more advanced techniques (it suggested a jellyfish). Am I missing something, or was it incorrectly advertised?

Code:
26.9.7.43
73.....89
.........
1..3.6..5
....7....
4..5.2..1
.........
34.....97
92.4.3.16


+-------------------------+-------------------------+-------------------------+
| 2       6       158     | 9       158     7       | 15      4       3       |
| 7       3       145     | 126     12456   145     | 156     8       9       |
| 58      1589    1489    | 168     3       148     | 167     567     2       |
+-------------------------+-------------------------+-------------------------+
| 1       789     289     | 3       489     6       | 24789   27      5       |
| 568     589     23689   | 18      7       1489    | 234689  236     48      |
| 4       789     3689    | 5       89      2       | 36789   367     1       |
+-------------------------+-------------------------+-------------------------+
| 568     158     168     | 7       12689   189     | 2348    235     48      |
| 3       4       1568    | 1268    12568   158     | 258     9       7       |
| 9       2       7       | 4       58      3       | 58      1       6       |
+-------------------------+-------------------------+-------------------------+


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PostPosted: Wed Jun 17, 2009 9:12 pm 
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It does require a Jellyfish after exhausting a regular heirarchy of solving techniques

Code:
*--------------------------------------------------------------------------*
| 2       6       158    | 9       158     7      | 15      4       3      |
| 7       3       145    | 126     12456   145    | 156     8       9      |
|*58      15-89   14-89  |*168     3      *148    | 167     567     2      |
|------------------------+------------------------+------------------------|
| 1       789     289    | 3       489     6      | 24789   27      5      |
|*568     5-89    236-89 |*18      7      *1489   | 2346-89 236    *48     |
| 4       789     3689   | 5       89      2      | 36789   367     1      |
|------------------------+------------------------+------------------------|
|*568     15-8    16-8   | 7       126-89 *189    | 234-8   235    *48     |
| 3       4       156-8  |*1268    1256-8 *158    | 25-8    9       7      |
| 9       2       7      | 4       58      3      | 58      1       6      |
*--------------------------------------------------------------------------*
Eliminating 8 From r357c2,r3578c3,r578c7,r78c5 (3x3x4x2 Jellyfish in Columns 1469)

Therefore it was not correctly advertised.

tarek


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PostPosted: Wed Jun 17, 2009 9:34 pm 
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ARRRRGGGGHHHH!!!! :brickwall: No wonder I was having trouble with it! :doh: I haven't gotten to jellyfish yet. This puzzle is one of a set of 5 from (I think) the Sudocue site that is supposed to help train a person to identify swordfish. I finished the other four, but this one had me stumped. Now I know why. Thanks, tarek!


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PostPosted: Thu Jun 18, 2009 9:50 am 
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The Pure Swordfish thread http://www.sudoku.com/boards/viewtopic.php?t=5775 at the Players' forum has many puzzles suitable for target practice.

tarek


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PostPosted: Thu Jun 18, 2009 6:38 pm 
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tarek wrote:
The Pure Swordfish thread http://www.sudoku.com/boards/viewtopic.php?t=5775 at the Players' forum has many puzzles suitable for target practice.

Thanks, tarek! I'll take a look. I think I have a pretty good handle on swordfish now, but it's very rare that I find one that actually eliminates any candidates.


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PostPosted: Tue Jul 07, 2009 3:38 pm 
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There is a swordfish which does the trick:

Code:
+-------------------+---------------------+------------------+
| 2     6      158   | 9      158     7    |  15      4    3 |
| 7     3      145   | 126    12456   145  |  156     8    9 |
| 58    1589   1489  | 168    3       148  |  167     567  2 |
+--------------------+---------------------+-----------------+
| 1    *789   *289   | 3     *489     6    | *24789   27   5 |
| 568   589    23689 | 18     7       1489 |  234689  236  48|
| 4    *789   *3689  | 5     *89      2    | *36789   367  1 |
+-------------------+----------------------+-----------------+
| 568   158    168   | 7      12689   189  |  2348    235  48|
| 3     4      1568  | 1268   12568   158  |  258     9    7 |
| 9     2      7     | 4     *58      3    | *58      1    6 |
+--------------------+---------------------+-----------------+


The cells open to 8 in rows 4, 6 and 9 must contain three 8s. These cells also fall into three other houses: box 4 and columns 5 and 7. So one 8 must go in each and no other cell in any of those three houses can contain an 8.

These eliminations (8 from r1c5, r5c123, r5c7, r7c57 and r8c5) reduce the puzzle to singles.

Steve


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PostPosted: Tue Jul 07, 2009 9:34 pm 
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congratulations steve for finding a fine fish ....

In absolute terms it is indeed a swordfish, however .....

Most published puzzles have been using the swordfish to incorporate only BASIC swordfish wich means 3 rows x 3 columns or 3 columns x 3 rows (NO BOXES)

What you have described is somthing called FRANKEN swordfish where boxes can be included in the 3 house x 3 house formation (NO mixing of rows and columns is allowed), IMO, this should have been explicitly mentioned beforehand. This shouldn't prevent us from admiring your fine catch....

When anything goes (mixing of rows, columns or boxes in any order in the 3x3 formation) then this is termed MUTANT swordfish .....

Here is are 2 examples with the same outcome from the above puzzle with 9 eliminations (The 2nd is actually Steve's catch ... Are you missing an elimination Steve ?).

Code:
8 forms a mutant  swordfish r9c9b5/r5c5b9 [r178c5][r5c1237][r78c7]<>8
8 forms a franken swordfish r4r6r9/c5c7b4 [r178c5][r5c1237][r78c7]<>8 (This is Steve's fine catch)


tarek


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PostPosted: Wed Jul 08, 2009 1:42 am 
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Yes, well spotted. I missed the elimination of 8 from r8c7.

Thanks, tarek.

Steve


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