Discuss the <a href="http://www.sudocue.net/daily.php">Daily Sudoku Nightmare</a> here
Ron Moore
Addict
Posts: 72 Joined: Sun Aug 13, 2006 3:34 am
Location: New Mexico
Post
by Ron Moore » Wed Apr 18, 2007 8:24 pm
[Edited to correct error in start position noted by Mike below]
Start position for the 17 April 2007 Daily Nightmare
Code: Select all
. . 7|. . 5|. 2 .
. 2 .|. 6 .|. 5 8
4 . .|2 . .|. . .
-----+-----+-----
. . 2|. 5 .|. . 9
. 1 .|6 . 7|. 4 .
5 . .|. 4 .|3 . .
-----+-----+-----
. . .|. . 9|. . 6
1 6 .|. 3 .|. 7 .
. 8 .|4 . .|1 . .
This is the position after initial basic eliminations:
Code: Select all
.------------------.-------------------.------------------.
| 68 39 7 | 1389 189 5 | 469 2 134 |
| 39 2 1 |*379 6 4 | 79 5 8 |
| 4 5 68 | 2 #1789 138 | 679 1369 *137 |
:------------------+-------------------+------------------:
| 678 4 2 | 138 5 138 | 678 168 9 |
| 389 1 389 | 6 289 7 | 258 4 25 |
| 5 *79 689 | 189 4 128 | 3 168 #127 |
:------------------+-------------------+------------------:
| 237 #37 345 | 158-7 1278 9 | 2458 38 6 |
| 1 6 459 | 58 3 28 | 24589 7 245 |
| 2379 8 359 | 4 27 6 | 1 39 235 |
'------------------'-------------------'------------------'
The following AIC for digit 7 is enough to complete the puzzle with only singles thereafter. (Cells in the chain are alternately marked with "*" and "#" in the diagram.)
(7): r2c4 = r3c5 - r3c9 = r6c9 - r6c2 = r7c2 => r7c4 <> 7
Last edited by
Ron Moore on Tue Apr 24, 2007 1:25 am, edited 2 times in total.
Para
Yokozuna
Posts: 384 Joined: Wed Nov 08, 2006 7:42 pm
Location: The Netherlands
Post
by Para » Wed Apr 18, 2007 9:23 pm
Hi
I generally prefer looking in patterns when solving sudoku's.
This can be recreated with this Finned Swordfish on 7 in C259 with R9C5 being the fin.
Code: Select all
.------------------.-------------------.------------------.
| 68 39 7 | 1389 189 5 | 469 2 134 |
| 39 2 1 | 379 6 4 | 79 5 8 |
| 4 5 68 | 2 *1789 138 | 679 1369 *137 |
:------------------+-------------------+------------------:
| 678 4 2 | 138 5 138 | 678 168 9 |
| 389 1 389 | 6 289 7 | 258 4 25 |
| 5 *79 689 | 189 4 128 | 3 168 *127 |
:------------------+-------------------+------------------:
| 237 *37 345 | 158-7 *1278 9 | 2458 38 6 |
| 1 6 459 | 58 3 28 | 24589 7 245 |
| 2379 8 359 | 4 #27 6 | 1 39 235 |
'------------------'-------------------'------------------'
greetings
Para
mhparker
Grandmaster
Posts: 345 Joined: Sat Jan 20, 2007 10:47 pm
Location: Germany
Post
by mhparker » Thu Apr 19, 2007 7:19 pm
As I understand it, Para's finned Swordfish would actually be equivalent to the AIC:
(7): r79c5 = r3c5 - r3c9 = r6c9 - r6c2 = r7c2 => r7c4 <> 7
where the fin belongs to the grouped node r79c5.
By the way, Ron, your "Start position" grid is incorrect in the top band. Maybe you can quickly fix that? Thanks.
Cheers,
Mike
Ron Moore
Addict
Posts: 72 Joined: Sun Aug 13, 2006 3:34 am
Location: New Mexico
Post
by Ron Moore » Tue Apr 24, 2007 1:25 am
Original post edited to correct the error Mike spotted -- thanks.
Yes, there's more than one way to view this. Grouped AIC's like the one Mike gives can always be written for empty rectangle and finned X-wing eliminations, and for finned 2-2-2 swordfish patterns like this one.