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 

Extra Hard 122017

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Other puzzles
View previous topic :: View next topic  
Author Message
immpy



Joined: 06 May 2017
Posts: 339

PostPosted: Wed Dec 20, 2017 1:33 pm    Post subject: Extra Hard 122017 Reply with quote

Enjoy the puzzle...Merry Christmas!

Code:

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

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



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Dec 21, 2017 4:13 am    Post subject: Reply with quote

here is after basics

Code:
┌──────────────────────────┬──────────────────────────┬──────────────────────────┐
│  36789      379      689 │   1356   124568     1238 │   1234      146     1346 │
│                          │                          │                          │
│     36        4        2 │      7       16        9 │      5        8      136 │
│                          │                          │                          │
│      5        1       68 │     36     2468      238 │    234        7        9 │
├──────────────────────────┼──────────────────────────┼──────────────────────────┤
│     67       57        1 │      8        3        4 │      9       56        2 │
│                          │                          │                          │
│   4689        2     5689 │    159     1579       17 │     14        3     1468 │
│                          │                          │                          │
│    489       59        3 │      2      159        6 │      7      145      148 │
├──────────────────────────┼──────────────────────────┼──────────────────────────┤
│      2        6        4 │     13      178     1378 │    138        9        5 │
│                          │                          │                          │
│    139        8        7 │      4       19        5 │      6        2       13 │
│                          │                          │                          │
│    139      359       59 │   1369    12689     1238 │   1348       14        7 │
└──────────────────────────┴──────────────────────────┴──────────────────────────┘

XY-Wing (36-1) pivot r3c4=> -1r1c4,r789c5

Here is after the XY-Wing


Code:
+---------------+----------------+---------------+
| 36789 379 689 | 5   12468 1238 | 1234 146 1346 |
| 36    4   2   | 7   16    9    | 5    8   136  |
| 5     1   68  | 36  2468  238  | 234  7   9    |
+---------------+----------------+---------------+
| 67    57  1   | 8   3     4    | 9    56  2    |
| 468   2   568 | 9   157   17   | 14   3   1468 |
| 489   59  3   | 2   15    6    | 7    145 148  |
+---------------+----------------+---------------+
| 2     6   4   | 13  78    378  | 138  9   5    |
| 13    8   7   | 4   9     5    | 6    2   13   |
| 139   359 59  | 136 268   238  | 1348 14  7    |
+---------------+----------------+---------------+


XY-Chain (9=5)r6c2- (5=76)r4c21-(6=319)r289c1=> -9r9c2,r6c1

here is after the XY-Chain

Code:
 +--------------+----------------+---------------+
| 36789 37 689 | 5   12468 1238 | 1234 146 1346 |
| 36    4  2   | 7   16    9    | 5    8   136  |
| 5     1  68  | 36  2468  238  | 234  7   9    |
+--------------+----------------+---------------+
| 67    57 1   | 8   3     4    | 9    56  2    |
| 468   2  568 | 9   157   17   | 14   3   1468 |
| 48    9  3   | 2   15    6    | 7    145 148  |
+--------------+----------------+---------------+
| 2     6  4   | 13  78    378  | 138  9   5    |
| 13    8  7   | 4   9     5    | 6    2   13   |
| 139   35 59  | 136 268   238  | 1348 14  7    |
+--------------+----------------+---------------+

One more wing finishes it.

XY-Wing (36-7) pivot r2c1=> -7r1c1,r4c2
Code:
Back to top
View user's profile Send private message
immpy



Joined: 06 May 2017
Posts: 339

PostPosted: Fri Dec 22, 2017 12:32 pm    Post subject: Reply with quote

Very nice Marty.
You are very good (it seems) with chains; I, unfortunately, am not. I get stupefied just trying to follow your path, and end up staring blankly at the puzzle, none the wiser. Consequently, this puzzle took me a bit longer to solve. I used the same initial XY- Wing (36-1), rinsed, found an X-Wing on 3 in r28 c19 which helped marginally, then basically resorted to looking for contradictions via the "if this is true...then that becomes" procedure. It always pays to keep a nice eraser handy...lol.
I eventually solved it, but your approach was by far quicker, and cleaner, as well.
Thanks, Marty, for posting it.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Other puzzles 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