dailysudoku.com :: View topic

dailysudoku.com
Discussion of Daily Sudoku puzzles

FAQ

Memberlist

Usergroups

Profile

Set H Puzzle 17
Goto page Previous 1, 2

dailysudoku.com Forum Index -> Puzzles by daj

View previous topic :: View next topic

Author

Message

Marty R.

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

Posted: Wed Dec 24, 2008 4:53 pm Post subject:

I wrote:

Quote:

In boxes 47, the 12 UR is both a Type 2 and Type 4. As a Type 4, the 6 is a strong link in c3 and after removing the 1s, just one 1 remains in c3.

I apologize to all who took the time and effort to respond to the above idiocy. I've executed hundreds of Type 4 URs--and have probably explained them to new players--but I just went brain-dead, probably due to creeping (galloping?) senility, by talking about the 6s as if they were one of the deadly candidates. Embarassed

keith

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

Posted: Wed Dec 24, 2008 6:27 pm Post subject:

Quote:

keith: Do you have an example of a UR Type 4 w/o this X-Wing pattern?

No, I do not.

Code:

+------------------------------------+
| / 123 / | / / 124| / / 18 | < no 2 in /
| . 167 . | 15 . . | . . . |
| . 12 . | . . 12 | . . . |
|------------+-----------+-----------|
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
|------------+-----------+-----------|
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+------------------------------------+

Every Type 4 UR is also an X-wing.

But, the logic for the example above is: One of the deadly candidates <12> cannot be in the UR cells in R1. If there are no other candidates <2> in R1, <2> must stay and <1> can be eliminated.

Of course, the X-wing is there, but we are really not using it.

To continue the controversy: The Type 4 UR eliminates the DP candidate that is NOT the X-wing candidate. So, what is the reason to do X-wings before UR's? I do not see how a UR can destroy an X-wing elimination.

Keith Razz

daj95376

Joined: 23 Aug 2008
Posts: 3854

Posted: Wed Dec 24, 2008 7:15 pm Post subject:

keith wrote:

Code:

Okay!!! I think we are finally on the same page. Smile

I use Simple Sudoku to highlight candidates (and pairs) when I'm manually looking for patterns. (I'd die if I had to use P&P!) The second I spot an X-Wing pattern for a candidate, I stop to see if there's a UR Type 4 present. On rare occasions, I'll remember to check for a UR Type 6. So, I use the X-Wing pattern.

Yes. Neither the X-Wing nor the UR would influence each other. But finding an X-Wing might lead one to stop and immediately check for a UR Type 4/6 in the cells from the X-Wing.

Thanks for a great exchange, Danny

Display posts from previous:

	dailysudoku.com Forum Index -> Puzzles by daj	All times are GMT Goto page Previous 1, 2
Page 2 of 2

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