dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Puzzle 11/04/28: ~ Difficult

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Puzzles by daj
View previous topic :: View next topic  
Author Message
daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Thu Apr 28, 2011 9:26 pm    Post subject: Puzzle 11/04/28: ~ Difficult Reply with quote
Hint wrote:
(early & late) 4-cell XY-Chain.

Code:
 +-----------------------+
 | 9 5 . | . 4 . | 2 . . |
 | 2 7 . | 3 . . | 4 6 . |
 | . . 8 | . . 7 | 3 . 9 |
 |-------+-------+-------|
 | . 2 . | 4 . . | 9 . . |
 | 5 . . | . 2 3 | 6 . . |
 | . . 4 | . 6 . | . . . |
 |-------+-------+-------|
 | 8 1 9 | 5 3 . | . . 6 |
 | . 4 . | . . . | . 3 . |
 | . . 2 | . . . | 5 . 1 |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
Back to top
View user's profile Send private message
peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK
PostPosted: Fri Apr 29, 2011 8:11 am    Post subject: Reply with quote
A UR xy-wing....
Quote:
(7=9)r6c4 - ur(67)r89c14[(9)r8c4=(8)r9c4] - (8=7)r9c5 ; r4c5<>7, r89c4<>7
Danny, how is your UR in chain() routine coming along? ... should make some interesting puzzles.
Back to top
View user's profile Send private message
daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Fri Apr 29, 2011 3:40 pm    Post subject: Reply with quote
peterj wrote:
Danny, how is your UR in chain() routine coming along? ... should make some interesting puzzles.

As you know from the pm that I sent, my SIN(network) routine now lists some interesting UR finds. What I did was add a UR detection sub-module to my routine that checks a grid for contradictions.

Today, I'm going to see how far I can get towards adding simple internal/external UR strong links to my chain() routine. My chain() routine is complicated enough that I've been dragging my feet on revisiting it. While I'm there, I may finish altering the chain detection sub-modules to support ALS relationships. I've already altered the data structures. Then I might (eventually) add simple ALS structures to my chain() routine.

Unfortunately, my puzzle generator is an offshoot of my first solver program. At some point, I may write a puzzle generator using my current solver and all of the additional techniques it supports. Right now, I generate puzzles with one set of logic, and then check them for interesting solutions using my current solver. It's a labor-intensive process to do a full cross-check of the puzzles. A process that I don't fully perform anymore.

Regards, Danny


===== ===== ===== ===== ===== for those who might be interested

Eureka Weekly Extreme #239 - SE 7.3

Code:
 +-----------------------+
 | . . . | . . . | . . . |
 | . . 9 | 4 7 3 | . . . |
 | . 3 . | . 1 . | . . 5 |
 |-------+-------+-------|
 | 6 8 1 | . 5 . | . . . |
 | . . . | . . . | . . . |
 | . . . | . 2 . | 9 1 3 |
 |-------+-------+-------|
 | 7 4 . | . . . | . 6 . |
 | . . . | 2 8 6 | 7 . . |
 | . . . | . . . | . . 9 |
 +-----------------------+

Code:
 <12> UR r19c12

 (7)r1c2  -                                               (  7)r3c3
 (6)r9c2  -                                   (  6)r2c2 = (6-7)r3c3
 (4)r1c1  -             (4=5)r6c1 - (5)r2c1 = (5-6)r2c2 = (6-7)r3c3
 (8)r19c1 - (8=4)r3c1 - (4=5)r6c1 - (5)r2c1 = (5-6)r2c2 = (6-7)r3c3
 -or-
 SIN assignments: 7r3c3  6r2c2  5r2c1  4r6c1  8r3c1  =>  <12> UR r19c12
 +-----------------------------------------------------------------------+
 | *12+48 *12+7   2478   |  89     6      5      |  12348  3479   12478  |
 |  1258   1256   9      |  4      7      3      |  1268   28     1268   |
 |  48     3      468-7  |  89     1      2      |  468    479    5      |
 |-----------------------+-----------------------+-----------------------|
 |  6      8      1      |  3      5      9      |  24     47     247    |
 |  39     29     23     |  1      4      7      |  568    58     68     |
 |  45     57     457    |  6      2      8      |  9      1      3      |
 |-----------------------+-----------------------+-----------------------|
 |  7      4      238    |  5      9      1      |  238    6      28     |
 |  39     159    35     |  2      8      6      |  7      34     14     |
 | *12+8  *12+6   268    |  7      3      4      |  1258   258    9      |
 +-----------------------------------------------------------------------+
 # 79 eliminations remain

Note: If you take the longest chain and perform it right-to-left as a set of assignments, then you get the SIN assignment sequence. That's why the list of "deductive" chains align so nicely!
Back to top
View user's profile Send private message
Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Apr 30, 2011 4:19 am    Post subject: Reply with quote
The 67 UR in boxes 78 needs an 8 in r9c4 or 9 in r8c4. The 8 forces a 9 in r6c6; r6c4<>9. Not sure how close this move is to Peter's.

Code:

+--------+-------------+---------+
| 9  5 3 | 68  4   16  | 2 17 78 |
| 2  7 1 | 3   589 589 | 4 6  58 |
| 4  6 8 | 2   15  7   | 3 15 9  |
+--------+-------------+---------+
| 1  2 6 | 4   578 58  | 9 57 3  |
| 5  9 7 | 1   2   3   | 6 8  4  |
| 3  8 4 | 79  6   59  | 1 2  57 |
+--------+-------------+---------+
| 8  1 9 | 5   3   2   | 7 4  6  |
| 67 4 5 | 679 179 16  | 8 3  2  |
| 67 3 2 | 678 78  4   | 5 9  1  |
+--------+-------------+---------+

Play this puzzle online at the Daily Sudoku site
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Puzzles by daj All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group