## Fish ?

Advanced methods and approaches for solving Sudoku puzzles

### Fish ?

This is an interesting puzzle.
Code: Select all
` +-------+-------+-------+ | . 5 . | . . . | 6 . 2 | | 4 3 . | . . . | . 9 . | | . . 1 | . 2 . | 7 . . | +-------+-------+-------+ | . 9 . | 3 . . | . . 4 | | . . . | 4 6 . | . . . | | . . . | . . 9 | . . . | +-------+-------+-------+ | 9 . . | . . . | . 7 . | | . . 5 | . 7 . | 2 3 . | | . 4 . | . . . | . . 1 | +-------+-------+-------+`
It can be solved by concentrating on the 8's.
Code: Select all
` +---------+----------+----------+ | .  .  . |  8  .  . |  .  8  . | | .  .  . |  .  8  . |  8  .  8 | | 8  8  . |  .  .  . |  .  .  . | +---------+----------+----------+ | 8  .  8 |  . -8  . | -8 -8  . | |-8 -8  . |  .  .  8 |  .  8  8 | |-8 -8  . |  8  8  . |  . -8  8 | +---------+----------+----------+ | .  .  8 |  8  .  8 |  .  .  8 | | 8  8  . |  8  .  . |  .  .  . | | .  .  . | -8  .  8 |  8  8  . | +---------+----------+----------+`
Is that a fish ?

Later 8 can be eliminated with a uniqueness pattern and a chain. The rest is not hard.

Other solutions ?
eleven

Posts: 2241
Joined: 10 February 2008

### Re: Fish ?

eleven wrote:Other solutions ?

I don't believe there is a single fish for your eliminations in 8. However, there are a number of finned Franken fish that get the job done.

Code: Select all
` +-----------------------+ | . 5 . | . . . | 6 . 2 | | 4 3 . | . . . | . 9 . | | . . 1 | . 2 . | 7 . . | |-------+-------+-------| | . 9 . | 3 . . | . . 4 | | . . . | 4 6 . | . . . | | . . . | . . 9 | . . . | |-------+-------+-------| | 9 . . | . . . | . 7 . | | . . 5 | . 7 . | 2 3 . | | . 4 . | . . . | . . 1 | +-----------------------+ r8  b7  Locked Candidate 1              <> 1    [r8c4]   c4b8  Locked Candidate 1              <> 5    [r6c4]Siamese  f  X-Wings   c39\r47|r67        <> 6    [r4c8],[r6c12]Siamese  fF Swordfish c36b9\r479|r579    <> 8    [r4c5],[r5c12]         fF X-Wing    c5b3\r26           <> 8    [r6c8]         fF Swordfish r15b8\c468         <> 8    [r4c8]         fF Jellyfish c359b4\r2467       <> 8    [r4c7] r4      Naked  Pair                     <> 15   [r4c18] r4  b4  Naked  Pair                     <> 68   [r6c12]   c1    Naked  Pair                     <> 68   [r8c1] r24     X-Wing                          <> 1    [r6c5]         XYZ-Wing [r5c8]/[r1c8]+[r4c7]   <> 1    [r6c8]         fF X-Wing    c7b2\r29           <> 8    [r9c4]`

Code: Select all
` *-----------------------------------------------------------* | 7     5     9     | 18    4     3     | 6     18    2     | | 4     3     2     | 7     18    6     | 158   9     58    | | 68    68    1     | 9     2     5     | 7     4     3     | |-------------------+-------------------+-------------------| | 68    9     68    | 3     15    7     | 15    2     4     | | 25    17    3     | 4     6     128   | 9     158   578   | | 25    17    4     | 128   58    9     | 3     56    5678  | |-------------------+-------------------+-------------------| | 9     2     68    | 1568  3     18    | 4     7     568   | | 1     68    5     | 68    7     4     | 2     3     9     | | 3     4     7     | 256   9     28    | 58    568   1     | *-----------------------------------------------------------*pick your favorite technique!`
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

### Re: Fish ?

Thank you, i will try to understand those Franken fish.
daj95376 wrote:
Code: Select all
`pick your favorite technique!`

There is a uniqueness pattern now, that eliminates 68 from r7c4, but is no help. To complete it with the 8:
r5c6=8 -> r5c1=2 -> r6c1=5 -> r6c5=8
eleven

Posts: 2241
Joined: 10 February 2008