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 

March 29 DB

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



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
PostPosted: Sat Mar 29, 2008 12:18 pm    Post subject: March 29 DB Reply with quote
The March 29 DB can be colored in 8's to solve R6C9 and the puzzle.

Earl


Code:

+-------+-------+-------+
| . . . | 9 . 1 | . . 7 |
| 7 . . | . 4 . | . . . |
| . 3 . | 2 . . | . . 9 |
+-------+-------+-------+
| . 7 . | . 5 3 | . 6 2 |
| . . . | . . . | . . . |
| 4 2 . | 6 1 . | . 5 . |
+-------+-------+-------+
| 3 . . | . . 7 | . 1 . |
| . . . | . 2 . | . . 5 |
| 9 . . | 3 . 4 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site
Back to top
View user's profile Send private message Send e-mail
keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Mar 29, 2008 1:43 pm    Post subject: Reply with quote
If you confine yourself to pencil marks only for cells that have two candidates, you will uncover a number of pairs, and then an easy to spot XY-wing.

If you look much harder, there is a Type 4 UR, but it does not help in the solution.

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



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat Mar 29, 2008 6:47 pm    Post subject: Reply with quote
definitely thought the UR was a harder route of travel. I thought it was rare that strong link within the same box on 8 would provide a color elimination.
Back to top
View user's profile Send private message
Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sat Mar 29, 2008 7:09 pm    Post subject: Reply with quote
I don't know if I made a lucky mistake, but this solved with basic moves only.

I tried Keith's method of putting in pencil marks only in two-candidate cells. I don't know if that makes solving easier, just saves some work, or something else.
Back to top
View user's profile Send private message
keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Mar 29, 2008 10:00 pm    Post subject: Reply with quote
Marty R. wrote:
I don't know if I made a lucky mistake, but this solved with basic moves only.

I tried Keith's method of putting in pencil marks only in two-candidate cells. I don't know if that makes solving easier, just saves some work, or something else.


Marty,

Here is my point, perhaps: If you solve all the singles, and fill in all the candidates, you are here:
Code:
Grid 1:
+----------------------+----------------------+----------------------+
| 2      4568   4568   | 9      3      1      | 4568   48     7      |
| 7      1569   1569   | 8      4      56     | 1356   2      136    |
| 1568   3      14568  | 2      7      56     | 14568  48     9      |
+----------------------+----------------------+----------------------+
| 18     7      189    | 4      5      3      | 189    6      2      |
| 1568   15689  135689 | 7      89     2      | 13489  3489   1348   |
| 4      2      389    | 6      1      89     | 7      5      38     |
+----------------------+----------------------+----------------------+
| 3      468    2      | 5      689    7      | 4689   1      468    |
| 68     468    7      | 1      2      689    | 34689  3489   5      |
| 9      15     15     | 3      68     4      | 2      7      68     |
+----------------------+----------------------+----------------------+

If you only fill in the cells with two candidates, you will get to here:
Code:
Grid 2:
+---------+---------+---------+
| 2  .  . | 9  3  1 | 56 48 7 |
| 7  .  . | 8  4  56| .  2  . |
| .  3  . | 2  7  56| .  48  9|
+---------+---------+---------+
| 18 7  . | 4  5  3 | .  6  2 |
| .  .  . | 7  89 2 | .  39 . |
| 4  2  . | 6  1  89| 7  5  38|
+---------+---------+---------+
| 3  .  2 | 5  .  7 | .  1  . |
| 68 .  7 | 1  2  89| .  39 5 |
| 9  15 15| 3  68 4 | 2  7  68|
+---------+---------+---------+

The solved cells are the same, the XY-wing that eliminates <9> in R5C5 is very obvious, and the puzzle is solved.

I prefer to go from Grid 2 to Grid 1 if necessary. If you prefer to simplify Grid 1, that's personal choice.

But, here, the two-candidate cells are all that is needed. I prefer to do only the two-candidate cells first; then, if need be, the three-candidate cells.

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 -> 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