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DB Saturday Puzzle - July 15, 2006

 
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Sat Jul 15, 2006 12:38 pm    Post subject: DB Saturday Puzzle - July 15, 2006 Reply with quote

Here is today's:

Puzzle: DB071506 ******
Code:
+-------+-------+-------+
| . . . | . . 2 | . 7 . |
| 3 . . | . 6 . | 8 . . |
| . 8 1 | . . . | 5 . . |
+-------+-------+-------+
| . . . | 9 . 3 | . . 6 |
| 9 1 . | . . . | . 4 7 |
| 6 . . | 4 . 7 | . . . |
+-------+-------+-------+
| . . 8 | . . . | 6 1 . |
| . . 6 | . 8 . | . . 3 |
| . 4 . | 5 . . | . . . |
+-------+-------+-------+

I got it down to where only two cells had three candidates (all the other unsolved cells had two candidates) and then solved it by coloring. Sudoku Susser says it has a Unique Rectangle.

Actually, I found the Friday puzzle to be more challenging:

Code:
Puzzle: DB071406  *****
+-------+-------+-------+
| . . . | . 3 5 | . . 6 |
| 6 . 4 | . . 2 | . . . |
| 5 . 7 | 8 . . | . . . |
+-------+-------+-------+
| . . 3 | . . . | . 1 . |
| 4 . . | . 8 . | . . 5 |
| . 9 . | . . . | 7 . . |
+-------+-------+-------+
| . . . | . . 8 | 1 . 2 |
| . . . | 6 . . | 5 . 3 |
| 2 . . | 9 5 . | . . . |
+-------+-------+-------+


This one I have not yet solved. Enjoy!

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sat Jul 15, 2006 5:04 pm    Post subject: Reply with quote

Keith, as to the July 14 puzzle, I suspect there's something there you're not seeing. But it provided me with a "first."

At the start, there were a lot of cells with a lot of candidates. But there was a single in one column, which opened up a naked pair, and from there, basic stuff got me down to seven unsolved cells, six with two possibilities and one with three, my first-ever BUG (or BUG+1) pattern.

I searched through the many pages I've printed out and found the one on BUG; I applied the rule and finished the puzzle. Of course, at that point, it would have been easily solvable with a simple chain, or perhaps coloring, but it was fun to apply the BUG rule for the first time.

I haven't yet started on the 15th.
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Sat Jul 15, 2006 6:24 pm    Post subject: Missing something? Reply with quote

Quote:
Keith, as to the July 14 puzzle, I suspect there's something there you're not seeing.


I'm sure that's the case. I'll be on a plane overnight, I'll crack it then. (I try to do these with no pencilmarks except for cells that have only two possibilities.)

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sat Jul 15, 2006 8:43 pm    Post subject: Reply with quote

Quote:
I try to do these with no pencilmarks except for cells that have only two possibilities.


Good luck. I am a fill-in-every-cell-with-all-its-candidates kind of guy. Maybe using fewer pencil marks will be a future goal.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Wed Jul 19, 2006 12:22 am    Post subject: Reply with quote

Keith wrote:
I try to do these with no pencilmarks except for cells that have only two possibilities.


But don't you still have to take the time to figure out how many possibilities are in each cell, so you know which ones only have two?

Once I've figured out how many possibilites are in a cell, and I don't care if there are 10, I write 'em in so I don't have to figure it out again later in the puzzle.
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Thu Jul 20, 2006 4:10 pm    Post subject: Fewer pencil marks Reply with quote

TKiel wrote:
... I don't care if there are 10 ...

Ten? Are you doing the "monster" puzzles now, Tracy? Smile

I generally try to do the Daily Sudoku puzzles without making any pencil marks, except for writing in the single values I'm sure of. When I do have to mark candidate lists, I'm with Keith -- I analyze all the pairs I can find first, before marking any of the cells with three or more candidates.

I used to mark up all the candidates, but found that this obscured my understanding of the structure underlying the puzzle. But then, that's just me. dcb

PS On several of Samgj's puzzles that required an X-Wing, I found that the X-Wing consisted of two pairs -- like {5, 7} in one column, and {7, 9} in another. So simply marking the pairs uncovered the X-Wing. In general, though, I do have to make extra marks to find an X-Wing.
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