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 

Scanning vs Cross Hatching

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Solving techniques, and terminology
View previous topic :: View next topic  
Author Message
gindaani



Joined: 06 Mar 2009
Posts: 79

PostPosted: Thu Apr 04, 2013 4:15 pm    Post subject: Scanning vs Cross Hatching Reply with quote

I was looking at the basic techniques on the Sudopedia mirror to put names to the techniques I use. I don't really understand how Scanning is different from Cross Hatching. There seems to be an implication that Scanning is somehow better, but I see no difference.

http://sudopedia.enjoysudoku.com/Scanning.html

Can anyone explain the difference?
Back to top
View user's profile Send private message
keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Sun Apr 07, 2013 8:00 am    Post subject: Re: Scanning vs Cross Hatching Reply with quote

gindaani wrote:
I was looking at the basic techniques on the Sudopedia mirror to put names to the techniques I use. I don't really understand how Scanning is different from Cross Hatching. There seems to be an implication that Scanning is somehow better, but I see no difference.

http://sudopedia.enjoysudoku.com/Scanning.html

Can anyone explain the difference?

I can't explain the difference. I suppose they are both things that I do, though I have never tried to explain them as algorithms.

I solve puzzles, as best I can, with pencil and paper, without pencil marks.

I start by scanning each floor of 3 rows to see where digits might be placed. Then, I scan each tower of three columns. But, with each tower, I am also looking at the intersecting floors. Then, I look at each digit in turn, to visualize how its pattern of unknowns fits in the puzzle.

In doing so, I have a theorem that quickly excludes candidates that cannot have single-digit eliminations from patterns like X-wings, kites or skyscrapers.

I tried to explain it once, and found no interest. Except Danny said, he knew that but had forgotten it!

Only then do I start looking at each row, column, and block for each digit 1-9.

Keith
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Solving techniques, and terminology 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