dailysudoku.com

RobertRattley · Joined: 24 Jun 2007 Posts: 118 Location: Australia

To you, Clement, was this only a "hard" puzzle?

I did see lots of 57s.

But my path was just one pair (your AD), a "hard" step. I like "very hard" puzzles that need a "hard" step, either before or after the "very hard" step(s).

Quite a bit more filling in. I wondered if it would turn out to be only a "hard" puzzle, but then I reached a point where I could see no way forward without a "very hard" step: a siamese twin xy wing 157 (that is, two closely related xy wings with your choice of pivot), deciding box 9.

I know that occasionally our consensus on this site is that a puzzle is misclassified. But I admit that my solving techniques are steered by knowledge of the classification. If a puzzle is "very hard", I assume I'll reach a point where a wing will be needed, and conversely if it is "hard" I'll be confident that I won't reach such a point.

I'll be interested to hear if others needed an xy wing in this puzzle.

TerenceF · Joined: 21 Dec 2007 Posts: 26 Location: Takapuna, NZ

I think you raise an interesting point, Robert, that one looks to use techniques that match the classification.

I arrived at a similar result starting with simpler techniques.

From Clement's grid, I spotted an X wing on 5 on rows 4 and 7 that eliminates the 5 from r8c4.

Then I used a 157 xy wing pivoted on r8c4 to eliminate the 5 from r9c2 and solve it.

So I was following your approach, and looking for the wings.

But I now see there is also a kite on 7 on row 4 and column 7 which can alternatively be used to eliminate the 7 fom r8c4 getting to the same result as Clement.

Would this be classified as a "not very hard" step?

btw, also a 157 XY wing pivoted in r8c3 which eliminates the 7 from r7c8 (but I didn't spot that at the time)

Clement · Posted: Sat Apr 20, 2013 2:06 pm Post subject: Apr 20 VH

RobertRattley,
I don't know whether it is a Hard or Very Hard puzzle as I did not compose it. What is important is a valid technique or logic which solves it. Why make easy things difficult?

RobertRattley · Joined: 24 Jun 2007 Posts: 118 Location: Australia

Thanks everyone.

I'm now confident that for us narrow-minded "purist" wing-ers this was properly classified as a "very hard" puzzle.

(I have come to understand from numerous posts in previous puzzles that on this site an intermediate puzzle does not need a pencil-mark stage, a hard puzzle does not need a wing, and a very hard puzzle needs, and can be solve by, one or more wings. Surely there will always be various other "advanced" techniques that may solve a puzzle, and there are often lively discussions on the merits of various alternatives to wing use, but I'm strictly a wing-er, even if I'm making things more difficult for myself, and I have solved every one of this site's very hards using only x-wings, xy-wings or xyz-wings. I might be comparable to a classical music lover who is intolerant of other forms of music.)

But what a delightful puzzle this one is! All 4s, 6s and 8s were fixed immediately, and as the puzzle sped forward one started to wonder if it was all going to fall into place with only "basics."

I'm still curious as to whether the creator of this site's puzzles discovers them or crafts them. If it's the latter, I remain in awe.

Marty R. · Posted: Sat Apr 20, 2013 3:16 pm Post subject:

RobertRattley · Joined: 24 Jun 2007 Posts: 118 Location: Australia

Thanks Marty.

Oh my, your reply was sent at the very minute I was crafting my augmentation of my second post! We crossed paths.

Your reply leaves me somewhat crestfallen. I guess I have to think the auto pilot is a very clever program.

Marty R. · Posted: Sat Apr 20, 2013 5:00 pm Post subject:

I know nothing about creating a puzzle, but I would think crafting it manually would be a tedious process. Many, if not most, of the sites that offer puzzles have thousands of them and computer generation seems a necessity.

RobertRattley · Joined: 24 Jun 2007 Posts: 118 Location: Australia

Yes.

I always assumed puzzle creation depended on computer use nowadays.

Legitimate puzzles are generated, and from a chosen set of solving techniques a classification can also be automated.

But since some of the very hards on this site over the years have been so gorgeous, I thought the creator must at least be intervening somehow, even if merely by screening.

I have a computing science degree from Adelaide, 1968. That's as anciently vintage as could be. My career(s) went in different directions, however, and I totally lost touch with the programming world. By the time the internet was developing, I was a professional computer user but no longer any kind of programmer. So I have a grasp of programmer mentality, and there are no mysteries for me. Perhaps it was naive of me to think that some master craftsman was behind the daily output from this site. Since posts on today's puzzle began, I did a bit of Googling and came to realize lots of people are in the Sudoku generating business.

Still, I can't let go. So I commend our auto pilot for creating such enjoyable puzzles, even if he has no conscious mind to receive my congratulations.