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 

Stuck on a toughie

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



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Tue Apr 18, 2006 4:56 pm    Post subject: Stuck on a toughie Reply with quote

I always have second thoughts about requesting help on these because of the possibility that I've made an error along the way and people work on something that's invalid to start with.

This is the strangest one I've encountered, because I've had an X-Wing, two swordfish, a block interaction, a forcing chain and unique X-Wing and still have hardly made a dent. Following my grid is the original.

Code:
----------------------------------------------------------
|9     4     8     |2     36    37    |5     1     367   |
|2     135   1367  |178   9     1357  |467   348   3678  |
|356   13    1367  |4     13568 137   |9     2     3678  |
----------------------------------------------------------
|58    89    2     |189   1348  6     |14    7     1359  |
|1     589   346   |789   348   3479  |46    3459  2     |
|36    7     346   |5     1234  12349 |8     349   1369  |
----------------------------------------------------------
|47    2     9     |3     145   8     |17    6     157   |
|38    138   13    |6     7     59    |2     59    4     |
|47    6     5     |19    124   1249  |3     89    1789  |
----------------------------------------------------------


Code:
--8---51-
2---9----
---4--9--
--2--6-7-
1-------2
-7-5--8--
--9--8---
----7---4
-65---3--
Back to top
View user's profile Send private message
keith



Joined: 19 Sep 2005
Posts: 3179
Location: near Detroit, Michigan, USA

PostPosted: Tue Apr 18, 2006 5:15 pm    Post subject: Bad news Reply with quote

Marty, the original code is a valid puzzle.

The grid you posted is not - it has no solutions.

Keith
Back to top
View user's profile Send private message
keith



Joined: 19 Sep 2005
Posts: 3179
Location: near Detroit, Michigan, USA

PostPosted: Wed Apr 19, 2006 12:24 am    Post subject: Reply with quote

Marty,

From your starting grid, without chains, I get to here:

Code:

+-------------------+-------------------+-------------------+
| 9     4     8     | 237   236   237   | 5     1     367   |
| 2     135   1367  | 1378  9     1357  | 467   348   3678  |
| 356   13    1367  | 4     13568 137   | 9     2     3678  |
+-------------------+-------------------+-------------------+
| 58    89    2     | 1389  1348  6     | 14    7     1359  |
| 1     589   346   | 3789  348   3479  | 46    3459  2     |
| 36    7     346   | 5     1234  12349 | 8     349   1369  |
+-------------------+-------------------+-------------------+
| 47    12    9     | 13    1345  8     | 127   6     157   |
| 38    1238  13    | 6     7     59    | 12    59    4     |
| 47    6     5     | 129   124   1249  | 3     89    1789  |
+-------------------+-------------------+-------------------+



And, I can tell you that R1C4 is NOT <2>. So far as I can see, your other values are correct.

Keith
Back to top
View user's profile Send private message
David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Wed Apr 19, 2006 12:46 pm    Post subject: r2c4 is not "3" Reply with quote

I agree with you, Keith, with one tiny exception. The "3" at r2c4 can be eliminated by a simple argument.

-- If r2c8 = 3 then clearly r2c4 <> 3.

-- If the "3" in box 3 lies in column 9 then r4c9 <> 3, and that leaves an X-Wing on "3" in rows 4 & 7, again implying that r2c4 <> 3.

I spent a little while looking for double-implication chains at this spot, without any success so far. This one is very difficult. dcb
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Wed Apr 19, 2006 4:40 pm    Post subject: Reply with quote

Quote:
The grid you posted is not - it has no solutions.

I must have known something when I talked about error possibilities in my post. I had been reluctant to erase everything and start over because I had put so much work into it, but I'll do just that now that I know for sure I've made errors.

Thanks to both of you.
Back to top
View user's profile Send private message
Guest






PostPosted: Thu Apr 20, 2006 9:50 pm    Post subject: Reply with quote

Uh, good luck, Marty,
this is a challenge, cant see a nice solution.
Back to top
ravel
Guest





PostPosted: Thu Apr 20, 2006 9:51 pm    Post subject: Reply with quote

you know it was me Smile
Back to top
Marty R.



Joined: 12 Feb 2006
Posts: 5164
Location: Rochester, NY, USA

PostPosted: Fri Apr 21, 2006 1:20 am    Post subject: Reply with quote

ravel wrote:
you know it was me Smile

Yup, sure did. You remind me of myself on another forum. I was an active poster as a Guest for two years before I registered. Don't ask why, I have no idea. Wink

OK, here we go again for the second and LAST time. After the erasure and restart, I've only been able to solve eight cells. My deep apologies if this has an error like the first grid I posted.

Code:
----------------------------------------------------------
|9     4     8     |237   236   237   |5     1     367   |
|2     135   1367  |1378  9     1357  |467   348   3678  |
|356   13    1367  |4     13568 137   |9     2     3678  |
----------------------------------------------------------
|58    89    2     |1389  1348  6     |14    7     1359  |
|1     589   346   |3789  348   3479  |46    3459  2     |
|36    7     346   |5     1234  12349 |8     349   1369  |
----------------------------------------------------------
|4     2     9     |13    135   8     |17    6     157   |
|38    138   13    |6     7     59    |2     59    4     |
|7     6     5     |129   124   124   |3     89    189   |
----------------------------------------------------------
Wink
Back to top
View user's profile Send private message
ravel
Guest





PostPosted: Fri Apr 21, 2006 8:29 am    Post subject: Reply with quote

The grid is ok, but I still only see a brute force method: There are only 2 ways to place the 5's, so one wrong 5 immediately leads to 5 others. But unfortuneately i dont get earlier, but later a contradiction ;(
Back to top
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