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 

May 9 Hard

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku puzzles
View previous topic :: View next topic  
Author Message
crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Fri May 09, 2008 12:46 pm    Post subject: May 9 Hard Reply with quote

I thought todays puzzle-hard-was especially tough for a non-vh puzzle.
Back to top
View user's profile Send private message
cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Fri May 09, 2008 1:03 pm    Post subject: Reply with quote

Agreed!!! Every now and then a “Hard” one pops up that is harder than most “VHs”. The problem is that “Hard” ones shouldn’t require advanced techniques such as ERs, URs or wings. So for these sudokus I only use my basic and primitive skills – just like Rambo. Probably more like Mr Bean – cos right now I’m stuck.
Back to top
View user's profile Send private message
stevieboy



Joined: 25 Jan 2008
Posts: 31
Location: Michigan

PostPosted: Fri May 09, 2008 3:36 pm    Post subject: Reply with quote

OK gang...here goes:

Since I don't know (yet) how to show the puzzle on my replies Crying or Very sad , I will try to describe, slowly, what I did to solve this puzzle. Again, I didn't do ANY xy-wings, UR's, etc. etc. I used the M-Wing method (Chapter 3) from the same link I referred to earlier:

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2143

(And), again, I used the SAME solving method I used in the vh of May 8 to solve that one...I will show you of all the "Strong Links" (ie, a pair along a Row or Column) that I used to solve this one correctly;
after basic eliminations, I did the following:

1. (First Strong Link) R9C4 TO R9C6 -> the STRONG LINK is '7'
2. (Second Strong Link) R9C6 To R4C6 -> the STRONG LINK is '7'
3. (Third Strong Link) R4C6 To R4C7 -> the STRONG LINK is '6'

...so the common cell for R9C4 and R4C7 is cell R9C7

R9C4 contains candidates '1 4 7'
R4C7 contains candidates '1 4 6'

USING THE M-Wing Rule of Chapter 3, we can then eliminate TWO(!!) COMMON CANDIDATES in R9C7 ---> '1' and '4' !!!!

THERE ARE A CRAPLOAD OF M-WINGS (or other facsimiles) IN THESE
SUDOKU'S...AND, THEY'VE ALL BEEN WORKING FOR ME!!

This was actually a trial for me, to see if a Double Candidate-Elimination would work...and, this one passed the test!

I may never have to use another xy-wing, etc. etc., if I don't have to Laughing

This is it (maybe?)...and, it REALLY is easy!! (Stevieboy says excitedly!)[/url]
Back to top
View user's profile Send private message
A.J.



Joined: 21 Mar 2008
Posts: 5
Location: San Diego, CA

PostPosted: Fri May 09, 2008 4:07 pm    Post subject: Reply with quote

I used the Block/Block interaction technique on this one. After the basics, if you look at blocks 4 and 6 you notice that 1s appear in only rows 4 and 6 in these two blocks. Therefore one of these blocks must have a 1 in row 4 and the other in row 6. Hence, all 1s can be eliminated in rows 4 and 6 in block 5. Smile It falls out with basics after that.
Back to top
View user's profile Send private message
Marty R.



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

PostPosted: Fri May 09, 2008 4:44 pm    Post subject: Reply with quote

Quote:
Since I don't know (yet) how to show the puzzle on my replies

There's an article on the Site Help forum on how to post an aligned grid.
Back to top
View user's profile Send private message
stevieboy



Joined: 25 Jan 2008
Posts: 31
Location: Michigan

PostPosted: Fri May 09, 2008 5:24 pm    Post subject: Reply with quote

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.
Back to top
View user's profile Send private message
stevieboy



Joined: 25 Jan 2008
Posts: 31
Location: Michigan

PostPosted: Fri May 09, 2008 5:40 pm    Post subject: Reply with quote

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.
Back to top
View user's profile Send private message
stevieboy



Joined: 25 Jan 2008
Posts: 31
Location: Michigan

PostPosted: Fri May 09, 2008 6:01 pm    Post subject: Reply with quote

Thanks, Marty.

Since I've been doing these puzzles on paper, I just haven't taken the time to transfer them online.
Back to top
View user's profile Send private message
cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Fri May 09, 2008 6:17 pm    Post subject: Reply with quote

A.J. Right off the bat there are a pair of 12's in Box 5 (R5C46). This means there can be no other 1's or 2's in Box 5 or Row 5. The rest of the puzzle can be solved by similar line/box eliminations. Though in this one it's hard to find the pairs and triples - I actually got stuck before spotting a single <3> (in Box 1 I think). But wings (including M wings Stevieboy) are definitely not needed for the hards.
Back to top
View user's profile Send private message
stevieboy



Joined: 25 Jan 2008
Posts: 31
Location: Michigan

PostPosted: Fri May 09, 2008 6:58 pm    Post subject: Reply with quote

...that may be true, cgordon, but not long after I did the same stuff you guys did (the 1-2 combo in Box 5 Row 5, which eliminated a lot of stuff in that area), I did the M-Wing, and we were in business...! Since I already had 2 candidates in most of the cells, this one was solved in minutes.

Hard, or very hard - it's sometimes hard to tell the difference.
Back to top
View user's profile Send private message
kermitbone



Joined: 07 May 2008
Posts: 4

PostPosted: Fri May 09, 2008 7:45 pm    Post subject: Reply with quote

I am still stuck on this one. I guess I still need a little help with the M-Wing. I was able to find the 12 double and the 67 double in box 5, but that didn't solve the puzzle for me.

This is where I am stuck
[
Code:

+-----------------+--------------+---------------+
| 4    5     129  | 2369  7 269  | 126  8    136 |
| 1236 12369 7    | 8     5 269  | 126  129  4   |
| 8    269   29   | 23469 1 2469 | 7    259  356 |
+-----------------+--------------+---------------+
| 13   1348  138  | 5     9 67   | 146  147  2   |
| 5    7     6    | 12    4 12   | 9    3    8   |
| 9    124   12   | 67    3 8    | 1456 1457 156 |
+-----------------+--------------+---------------+
| 1236 12369 4    | 19    8 159  | 1235 125  7   |
| 7    129   1259 | 149   6 3    | 8    1245 15  |
| 13   138   1358 | 147   2 1457 | 1345 6    9   |
+-----------------+--------------+---------------+


I was trying to follow stevieboys M wing and I kinda got it, but that didn't solve it for me either.

Any other thoughts?

Thanks,
Back to top
View user's profile Send private message
kermitbone



Joined: 07 May 2008
Posts: 4

PostPosted: Fri May 09, 2008 7:49 pm    Post subject: Reply with quote

Looking at my own post, I see the 13 double in Column 1 which should help me significantly. As far as the M-Wing, was I just not able to see it, because I hadn't gotten the 13 double yet?

I am getting there...

Thanks,
Back to top
View user's profile Send private message
storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Fri May 09, 2008 7:58 pm    Post subject: Reply with quote



the naked pair in row 5 helps a lot in the image above. removes all the 1's and 2's they can see.



the {1,3} naked pair opens up and it should be smooth from there.

at this point you can solve it if you pay close attention to the singles in rows and boxes etc.
Back to top
View user's profile Send private message
crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Sat May 10, 2008 12:47 am    Post subject: Reply with quote

I solved this with no wings of any kind, and no URs, or ERS. Line or box line reductions were required. Maybe a naked quad, but can't remember for sure. But indeed this sucker was tough.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku 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