SudokuSolver Forum

A forum for Sudoku enthusiasts to share puzzles, techniques and software
It is currently Thu Mar 28, 2024 2:01 pm

All times are UTC




Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: Is this an XY-wing?
PostPosted: Sat Jun 20, 2009 2:23 pm 
Offline
Grand Master
Grand Master
User avatar

Joined: Thu Apr 24, 2008 4:27 pm
Posts: 791
Code:
.   .   .   |   .   .   .   |   .   .   .
.   .   .   |   .   .   .   |   .   .   .
.   57  .   |   47  .   .   |   .   .   .
-----------------------------------------
.   .   .   |   .   .   .   |   .   .   .
.   .   .   |   .   .   .   |   .   .   .
.   .   .   |   .   .   .   |   .   .   .
-----------------------------------------
.   .   .   |   45  .   .   |   .   .   .
.   .   .   |   .   .   .   |   .   .   .
.   .   .   |   .   .   .   |   .   .   .


Am I correct that this pattern would eliminate all other 7s in r3 and all other 4s in c4?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jun 20, 2009 2:56 pm 
Offline
Grand Master
Grand Master

Joined: Mon Apr 21, 2008 9:44 am
Posts: 310
Location: MV, Germany
This is an XY-Wing but it does not eliminate the candidates you mentioned. In this case the only elimination you could make is R7C2 <> 5. Here is how:

If R3C4 = 4, then R7C4 = 5
If R3C4 = 7, then R3C2 = 5.

So no matter what the placement of R3C4 is, one of R3C2 and R7C4 must be 5. So all cells which see both of them, cannot be 5. Therefore R7C2 <> 5 since it sees R3C2 and R7C4.


Top
 Profile  
Reply with quote  
 Post subject: Re: Is this an XY-wing?
PostPosted: Sat Jun 20, 2009 6:20 pm 
Offline
Grand Master
Grand Master
User avatar

Joined: Thu Apr 24, 2008 4:27 pm
Posts: 791
Ok, I see that. Thanks! I think that's where I made my mistake on this puzzle on the last attempt. It makes the logic a lot more clear to see the three cells without all of the candidates in the other cells.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 2 guests


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 post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group