dailysudoku.com

keith · Posted: Sat Mar 11, 2006 9:15 am Post subject: DB Saturday puzzle (March 11)

Here is today's David Bodycombe puzzle. I had fun with it.

Keith

Steve R · Posted: Sat Mar 11, 2006 5:36 pm Post subject: Very hard becomes a nightmare

Thanks for DB’s latest, Keith. Like you I enjoyed it considerably, though it was tough going by my standards.

In fact it was the second hard slog of the week, the first being samgj’s very hard of 9 March. You might like to try it after moving the 7 in row 1 one cell to the left. This is the result:

David Bryant · Joined: 29 Jul 2005 Posts: 559 Location: Denver, Colorado

I liked the Bodycombe puzzle too -- coloring on the "7"s plus one XY-Wing did the trick for me.

Steve, I'm curious how you found the permutation on samgj's puzzle. Do you often look for slight alterations like that? How often does a valid puzzle result? dcb

Steve R · Posted: Sat Mar 11, 2006 9:22 pm Post subject: It's a good puzzle

No. I put it in a solver to check that it involved more than singles, made a transcription error and became interested.

I have tinkered with puzzles on only three occasions, using a solver to see if the symmetric original could be reconstructed from partially worked grids found on web sites. I succeeded the first time but on each occasion stumbled through too many multiple solution or invalid grids to recommend the practice.

Steve

Marty R. · Posted: Sat Mar 11, 2006 11:48 pm Post subject:

Keith, I also like that you post these DB puzzles. This one I was able to solve with the use of two forcing chains.

keith · Posted: Sun Mar 12, 2006 12:46 am Post subject: Reasons to post puzzles

Marty, Steve, David, and all:

I have been posting these puzzles only when they involve something more than "basic" techniques.

I think of basic techniques as forced and pinned values, naked and hidden sets, and row / block / column interactions. I have not yet seen a Daily Sudoku that requires more than these techniques.

The next (intermediate?) level includes X and XY-wings, swordfish, unique rectangles, BUG patterns, simple coloring, and the like. The DB puzzles I have posted involve these.

I think of the various chain techniques as "advanced", possibly because I have such difficulty seeing them.

Anyway, I am not trying to start a debate on classification of solution strategies. This is a long way of explaining why I posted three puzzles two weeks ago, none last week, and only one this week.

Keith

David Bryant · Joined: 29 Jul 2005 Posts: 559 Location: Denver, Colorado

someone_somewhere · Joined: 07 Aug 2005 Posts: 275 Location: Munich

Hi,
could not resist to take a look at this one.
I found a nice 5 star in the following places:
r2c6 = 47
r2c7 = 47
r3c5 = 347
r9c5 = 47
r9c7 = 47
Staring with r2c6 as alpha and following only the digit 4 (which means coloring!!!):
r2c6 = 4 r2c7 <> 4 r9c7 = 4
r2c6 = 4 r3c5 <> 4 r9c5 = 4

And this is excluding 4 from r2c6, because of contradiction in row 9.

Nice one, thank you.

see u next week,