Further swordfish example

rubylips · Posted: Sun Apr 24, 2005 5:00 am Post subject: Further swordfish example

The following puzzle contains a swordfish pattern that, when found, allows completion without guesses:

rubylips · Posted: Sun Apr 24, 2005 10:28 am Post subject:

Another swordfish puzzle:

Simes · Posted: Sun Apr 24, 2005 6:38 pm Post subject:

sorry again rubylips, but the second example doesn't need swordfish.

rubylips · Posted: Sun Apr 24, 2005 7:36 pm Post subject:

Do I have yet another bug in my solver? Without swordfish, I reach the following position:

Simes · Posted: Mon Apr 25, 2005 7:13 am Post subject:

Now that's curious. When I paste in your part-complete example, my program doesn't find a solution. But when I paste in the original, it does find a solution. Hmmm.

Here's the log from the original puzzle:

Note: Cell coordinates are in (column,row) format
(3,3) = 4 : only cell in column 3 that can contain 4
(7,9) = 2 : only cell in column 7 that can contain 2
(1,3) = 7 : only cell in row 3 that can contain 7
(6,4) = 7 : only cell in row 4 that can contain 7
(3,6) = 7 : only cell in row 6 that can contain 7
(5,9) = 4 : only cell in row 9 that can contain 4
(6,6) = 5 : only cell in block 5 that can contain 5
(5,8) = 7 : only cell in block 8 that can contain 7
(7,7) = 4 : only cell in block 9 that can contain 4
block 4: column 2 must contain 3, removing 3 from candidates for cell(s) (2,1)(2,3)
block 4: column 1 must contain 8, removing 8 from candidates for cell(s) (1,9)
block 7: row 9 must contain 5, removing 5 from candidates for cell(s) (8,9)(9,9)
block 7: column 3 must contain 6, removing 6 from candidates for cell(s) (3,1)(3,2)
block 5: row 5 must contain 6, removing 6 from candidates for cell(s) (1,5)(2,5)(9,5)
block 8: row 7 must contain 5, removing 5 from candidates for cell(s) (8,7)(9,7)
block 3: row 1 must contain 1, removing 1 from candidates for cell(s) (2,1)(3,1)(4,1)(5,1)
block 6: row 4 must contain 6, removing 6 from candidates for cell(s) (2,4)
(5,7) = 5 : only possible value for this cell
(3,1) = 3 : only cell in column 3 that can contain 3
(4,5) = 1 : only cell in column 4 that can contain 1
(2,5) = 4 : only cell in row 5 that can contain 4
(4,4) = 4 : only cell in block 5 that can contain 4
column 7: unique subset 589 in cells (7,1)(7,2)(7,3) - updating candidates for cell(s) (7,4)(7,8)
row 1: unique subset 25689 in cells (1,1)(2,1)(4,1)(5,1)(7,1) - updating candidates for cell(s) (8,1)(9,1)
row 5: unique subset 89 in cells (1,5)(9,5) - updating candidates for cell(s) (8,5)
row 8: unique subset 368 in cells (3,8)(4,8)(7,8) - updating candidates for cell(s) (9,8)
block 1: unique subset 19 in cells (3,2)(2,3) - updating candidates for cell(s) (1,1)(2,1)(1,2)
(9,8) = 5 : only possible value for this cell
(8,4) = 5 : only cell in column 8 that can contain 5
row 1: unique subset 12567 in cells (1,1)(2,1)(5,1)(8,1)(9,1) - updating candidates for cell(s) (4,1)(7,1)
block 3: unique subset 1789 in cells (7,1)(8,1)(9,1)(7,3) - updating candidates for cell(s) (7,2)
(7,2) = 5 : only possible value for this cell
(4,6) = 2 : only cell in column 4 that can contain 2
(8,5) = 2 : only cell in column 8 that can contain 2
blocks 2 and 5 must contain 3 in columns 5 and 6 - removing 3 from candidates for cell(s) (6,9)
(4,8) = 3 : only cell in column 4 that can contain 3
(7,4) = 3 : only cell in column 7 that can contain 3
(8,9) = 3 : only cell in column 8 that can contain 3
(9,4) = 6 : only cell in row 4 that can contain 6
(2,6) = 3 : only cell in row 6 that can contain 3
(3,7) = 6 : only cell in row 7 that can contain 6
(7,8) = 6 : only cell in row 8 that can contain 6
(3,8) = 8 : only cell in row 8 that can contain 8
(9,9) = 7 : only cell in row 9 that can contain 7
(1,6) = 6 : only cell in block 4 that can contain 6
(8,1) = 7 : only cell in block 3 that can contain 7
(9,5) = 9 : only cell in block 6 that can contain 9
block 1: row 1 must contain 6, removing 6 from candidates for cell(s) (5,1)
block 4: column 2 must contain 9, removing 9 from candidates for cell(s) (2,3)(2,9)
block 7: row 9 must contain 9, removing 9 from candidates for cell(s) (6,9)
block 8: column 4 must contain 9, removing 9 from candidates for cell(s) (4,1)
block 3: column 9 must contain 1, removing 1 from candidates for cell(s) (9,7)
block 6: column 8 must contain 8, removing 8 from candidates for cell(s) (8,7)
block 9: row 7 must contain 8, removing 8 from candidates for cell(s) (4,7)
(1,2) = 2 : only possible value for this cell
(1,5) = 8 : only possible value for this cell
(2,3) = 1 : only possible value for this cell
(2,4) = 9 : only possible value for this cell
(2,9) = 5 : only possible value for this cell
(3,2) = 9 : only possible value for this cell
(3,9) = 1 : only possible value for this cell
(4,1) = 8 : only possible value for this cell
(4,7) = 9 : only possible value for this cell
(5,1) = 2 : only possible value for this cell
(5,3) = 3 : only possible value for this cell
(5,5) = 6 : only possible value for this cell
(6,2) = 6 : only possible value for this cell
(6,3) = 9 : only possible value for this cell
(6,5) = 3 : only possible value for this cell
(6,9) = 8 : only possible value for this cell
(7,1) = 9 : only possible value for this cell
(7,3) = 8 : only possible value for this cell
(8,6) = 8 : only possible value for this cell
(8,7) = 1 : only possible value for this cell
(9,1) = 1 : only possible value for this cell
(9,7) = 8 : only possible value for this cell
(1,1) = 5 : only cell in column 1 that can contain 5
(1,9) = 9 : only cell in column 1 that can contain 9
(2,1) = 6 : only cell in column 2 that can contain 6
(5,2) = 1 : only cell in column 5 that can contain 1
Completed

resulting in:
563824971
289716543
714539862
192487356
845163729
637295184
376952418
428371695
951648237

Does that match your solution or is there more than one?

rubylips · Posted: Mon Apr 25, 2005 9:53 pm Post subject:

First, I did have a bug in my solver (the 'performance enhancement' again - I've just stripped it out completely!). The solver now confirms that it's not necessary to find a swordfish in order to complete the puzzle.

Secondly, the fact that your solver isn't able to complete the partially-solved puzzle suggests that it has a bug. Here's the output from my solver for the first move, after which all is plain sailing:

The value 1 in Row 1 must lie in Box [1,3].
The value 6 in Box [2,1] must lie in Row 6.
The value 6 in Box [2,3] must lie in Row 4.
The value 6 in Column 3 must lie in Box [3,1].
The value 8 in Box [3,1] must lie in Column 3.
The values 1 and 7 occupy the cells (1,8) and (1,9) in some order.
The value 8 in Column 7 must lie in Box [1,3].
The value 9 in Box [2,3] must lie in Column 9.
The values 2, 3 and 6 occupy the cells (5,5), (5,6) and (5,8) in some order.
The values 2, 5 and 6 occupy the cells (1,1), (1,2) and (2,1) in some order.
The values 8 and 9 occupy the cells (1,4) and (1,7) in some order.

The cell (6,4) is the only candidate for the value 2 in Column 4.

Thirdly, here's a new swordfish puzzle:

Tempbow · Posted: Mon Apr 25, 2005 11:40 pm Post subject: What is missing?

Message moved to new topic

Tempbow · Posted: Tue Apr 26, 2005 6:24 am Post subject:

Message moved to new topic "Difficult Problems"

Tempbow · Posted: Tue Apr 26, 2005 6:27 am Post subject:

Oops, sorry, my last two postings should really have been a new topic, rather than under the Swordfish thread Crying or Very sad

I have now moved them to the new topic "Difficult Problems"
They defined problems that XWINGS and SWORDFISH did not resolve.

Simes · Posted: Tue Apr 26, 2005 7:05 am Post subject:

Rublips,