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Puzzle 11/04/28: ~ Difficult

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

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
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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.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

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!
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Marty R.



Joined: 12 Feb 2006
Posts: 5176
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  |
+--------+-------------+---------+

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