Swordfish compendium

rubylips · Posted: Tue Apr 26, 2005 11:27 am Post subject: Swordfish compendium

I know that I've thrown up a few red herrings over the past couple of weeks but I now think I've firmly got to grips with the swordfish - thanks to plenty of help from simes and IJ. Here's a compendium of puzzles, each of which is able to be solved logically (no Nishio) provided that the swordfish is found. Some of the puzzles are new while others have been lifted from existing topics.

Puzzle 1:

rubylips · Posted: Tue Apr 26, 2005 9:14 pm Post subject:

Puzzle 6:

Animator · Posted: Wed Apr 27, 2005 1:53 pm Post subject:

Are you sure puzzle 5 and 7 are correct?

Tempbow · Posted: Sat Apr 30, 2005 2:07 am Post subject:

IJ · Posted: Sun May 01, 2005 12:35 am Post subject:

Is Puzzle 4 OK? I can solve all the others, but No 4 just ends up in a mess. I'm guessing I have a bug somewhere, but would appreciate another view...

Animator · Posted: Sun May 01, 2005 11:20 am Post subject:

I solved them all except puzzle 5 (that is to say, without hints from here)

If you need a hint, then feel free to PM me... I prefer not to post it here since it may spoil the fun for some other people...

IJ · Posted: Sun May 01, 2005 8:33 pm Post subject:

Thanks - I found the bug.

My code now solves puzzle 5 - based on the notes I made on your other post.

AMcK · Posted: Fri May 20, 2005 10:57 am Post subject: Great puzzles!

Thanks to Rubylips for excellent 7 puzzles.
All solvable using colouring.
Puzzle 5 hardest because of conjugates in digts 3 and 5 and failure of colouring to reduce to single digit leaving N=3 work to complete.

Code:

Puzzle 1:
Colouring for digit: 6

- - - - - - * - -
- - a b - - - - -
- b * - a - - - -
- a - - - - - - b
- - - - - * - - -
- - b - - - - a -
* - - - - - - - -
- - - a - - - b -
- - - * b - - - a

Row 3 reduction: digit 6 colours b/a cell {3,3} before 69 after 9
Row 9 reduction: digit 6 colours b/a cell {9,4} before 2456 after 245

Puzzle 2:
Colouring for digit: 2

- - * - - - - - -
- - - - - a b - -
- - - b - - * a -
* a - - - - - b -
b - - - - - a - -
- - - - * - - - -
- - - - - - - - *
- b - a - - - - -
a - - - - b - - -

Row 3 reduction: digit 2 colours b/a cell {3,7} before 25 after 5
Row 4 reduction: digit 2 colours a/b cell {4,1} before 2349 after 349

Puzzle 3:

Colouring for digit: 1
- a - - - - - - b
e * - - - f - - -
- - - - e - d - *
- - * - - - - - -
- - - - - - c - d
- - - f * e - - -
- - - - - - - * -
- e - - f - - - -
f - - e - - - - -

Row 2 reduction: digit 1 colours e/f cell {2,2} before 178 after 78
Row 6 reduction: digit 1 colours f/e cell {6,5} before 14 after 4

Puzzle 4:
Colouring for digit: 5
- - - * b - - a -
* - - - - - - - -
- - - a - - b - -
- a * - - - * b -
- - c - - - d - -
- - - - - * - - -
- - a b - - - - -
- - - - - - - - *
- b - - a - - - -

Row 1 reduction: digit 5 colours b/a cell {1,4} before 257 after 27
Row 4 reduction: digit 5 colours a/b cell {4,3} before 1578 after 178
Row 4 reduction: digit 5 colours a/b cell {4,7} before 25 after 2

Puzzle 5:
Colouring for digit: 3
c - * - - d b - -
- * * - - - - - *
- * - - c - - - *
- * - d - * - - -
- * * - - * - - -
- - - - - - a - b
- c - - d - - - -
d - * c - - - - -
- - - - - - - * -

Row 1 reduction: digit 3 colours c/d cell {1,3} before 2357 after 257
Row 1 reduction: digit 3 colours c/d cell {1,7} before 138 after 18
Row 8 reduction: digit 3 colours d/c cell {8,3} before 2357 after 257

Colouring for digit: 5
- - a - - b - - -
- - - - - - - * -
- b - - a - - - -
- - - b - a - - -
- - - - - - * - -
* - - - - - - - -
- * - - b - - - i
- - b a - - - - -
- * * - - - - - j

Column 3 reduction: digit 5 colours a/b cell {9,3} before 257 after 27

Puzzle 6:
Colouring for digit: 4
- a - - - b - - -
- - - - - - - - *
- - b - a - - - -
- - a - - - - b -
- - - * - - - - -
- b - - - - a - -
- - - - b * - a -
- - - - - a b - -
* - - - - - - - -

Row 7 reduction: digit 4 colours b/a cell {7,6} before 49 after 9

Puzzle 7:
Colouring for digit: 1
- * b - - - - a -
a - - b - - - - -
* - - - - a - b -
- c - - - - d - -
d - - - - - c - -
- - - - * - - - -
* * - a - - - - -
- - a - - b - - -
- - - - - - - - *

Row 1 reduction: digit 1 colours b/a cell {1,2} before 13 after 3
Row 3 reduction: digit 1 colours a/b cell {3,1} before 134 after 34

Best regards
Andrew

bking43 · Posted: Fri Jun 03, 2005 5:04 pm Post subject: Ok, how about harder?

I took a quick peek at the first puzzle listed in this thread and solved it without much difficulty. I did need to figure out one new technique, which I presume is what people are calling "swordfish", though I haven't read the definition of that term.

I shall try the rest, but would like more of a challenge. So far I have worked a total of 5 sudoku puzzles, ranging from 2 easy, 1 medium, 1 hard and 1 swordfish.

Is there anything out there that is harder, but which can still be solved using logic alone (not requiring me writing a program to solve? I could, but have more fun doing these things with pen and paper.)

FWIW, I spent 8 years sucessfully pursuing degrees in mathematics (topology) many years ago, and have spent my adult life writing and designing computer programs and systems. I love logic.

Please feel free to reply to my email address or to here.
TIA, bking43@yahoo.com.
_________________
bking43
.sig shows an old guy juggling 5 balls in a pattern every juggler knows is bogus.

abailes · Posted: Tue Jun 07, 2005 8:22 pm Post subject:

bking,

Try your hand at this one:

http://www.sudoku.com/forums/viewtopic.php?t=387

And solve without trial and error.

I remain unconvinced there is not another nice sudoku theory lurking out there (although it will probably be impossible to spot in a puzzle if you find it).

Andrew