seemed like a pretty easy "hard"

go

done

very easy "hard"

Done

someone that does these in two minutes, equals lazy cheaters! plan and simple.

someone that does these in two minutes, equals lazy cheaters! plan and simple.

someone that does these in two minutes, equals lazy cheaters! plan and simple.

it's a brain teaser not use autofill or some cheat program.

go

done

done

go

done

go

neone else get stuck?

not so far, doing all the puzzles I missed during my vacation.

I did for a minute - found a singleton in the rightmost column

im doing todays, and im stuck, which one is the singleton?

sorry, what is a singleton, thats the better way of phrasing it

I guess it is a cell for which there is only one value left?

done after a very long interruption.

used greens. Bran fuzzy. Shouldn't have had that martini last night.

nice...easiest 'hard' in a coupla weeks!

22. Going green.

Okay, there's a pair I didn't see w/o greens.

doing August 8's now. August 7's was tough!

Done. Easy with greens. With a little more persistence, I should have done it w/o greens.

well done anyway

Difficulty score 22, well below the average score of 31.38 for hard puzzles. I thought yesterday's hard was easier. Look for a hidden pair.

dr. who, was August 7 a real tough one?

this could be a silly question, but how do you rate the puzzles?

I didn't think so, and my program only scored it a 33. See:
http://www.pauls-pc-repair.com/sudoku/in
dex.html
for an explanation of scores and a link to a table of scores I have generated for the IronSudoku puzzles.

August 7 was tough. It had an x-wing not too hard to find It contained a number "which doesn't belong." I can only explain that by saying a bunch of pairs was complete without that number. And I'm not even sure if my logic is correct, but it worked out that I could eliminate the stray number. Even so, I had to guess later on.

*sigh*
Must be really out of training then... I did a lot of master rated puzzles with pen and paper... but they are much easier than the ones here.

Many sites limit their puzzles to ones which can be solved by a set of well known solving techniques. Apparently here that is not the case for the Expert puzzles.

oooh... very interesting. thanks!

I think so too. I have these booklets from the tazuku series, they rate from 4 to 6 stars and they rarely give me real problems. But the experts here can.

If you're looking at my web site you might be interested in trying the online rating program. It generates slightly different scores than the program I use here.

you gave me that link before and I did check it out. Very interesting site. Perhaps I should check some of the 6-starred puzzles from the booklet and see how they turn out in your rating program.

I give a number calculated by almost the same method I use to rate puzzles here, plus I rate it Easy, Medium, Hard or Expert by the same method Dr. God uses here.

I think I will check out a few of the socalled tough puzzles from the booklet. I am really curious whether I am better with pen and paper than on line, or that the puzzles here are tougher (the expert ones anyway). I think the latter.

If I wanted to sell a book of Sudoku puzzles to as many people as possible, I think I would limit the difficulty so I wouldn't scare away potential customers.

Speaking of publishing puzzles, my next project will be to write a program to generate Sudoku puzzles.

I am not sure about that. They have booklets with 1-3 stars, 1-5 stars, 3-5 stars, 4-6 stars and so on. So I would think that the highest levels should be really challenging, to keep it interesting for the more experienced player. They will want them as regular customers.

Let me know how that goes.

nice drwho! Keep us informed!

Ok, I won't be able to do it in JavaScript (which is how the online solver and rating program is written), but I may be able to put a CGI interface on a Linux program and make it available online. I still have a lot to learn about web programming.

sounds like a challenge in itself.
So... caught up with the puzzles, on to today's :)

My online solver can almost do it now. Just tell it to solve a puzzle with no clues. Your browser will think my program is running too long, but if you let it run long enough it will give you a filled in grid with a proper solution. The trick is to figure out what to use as clues for that "solution", that and to put in some randomness to the solutions it generates.

Does that produce only unique puzzles?

No, it doesn't actually produce puzzles (no clues!), just a solution (all the numbers filled in).

but I can see how that will lead to creating solvable puzzles. It would suffice to let it create a complete puzzle and then go back enough steps to make the puzzle challenging AND solvable.

So if you take that filled in grid and eliminate a bunch of numbers, then can you tell if this is a unique puzzle?

The first step in generating a puzzle is to generate its solution, then figure out what to give as the clues and then verify that the solution is unique.

Verifying uniqueness is simple, generating the clues, or deciding which numbers not to eliminate, could be tricky.

It is conceivable that I could give all but 4 numbers of the solution as clues and still not have a unique solution (anybody heard of unique rectangles? :-).

just what I was thinking. What clues do you give to make it possible to solve the puzzle, yet tough enough to be interesting... and there would the rating help, I think. Which solving techniques are needed.

I used unique rectangles pretty often. They are purely based on the assumption it is a GOOD puzzle, one with only one solution :)

*use, not used

Right now, I don't have any idea on how to select the clues with the goal of producing easy or hard puzzles.

it might be connected with the rating. I am really looking forward to hearing how you tackle the problems, drwho!

When I get it working I will at least put up an explanation of how it works on my web site. I hope also to integrate it into my online solver so it will be able to solve puzzles you enter or generate random puzzle for you to solve.

that would be really great. I hope you get it working the way you want!

today's wasn't bad at all. No greens needed, and no techniques other than the obvious.

breezed through this one alright

hmm. it was easy up to a point, but now I'm stuck

done

easy

and yet still at newbie at 237, humpf!

hi everyone

hmm

lotsa - whaddayacallem? triples?

ah - found a 9 and now i'm on my way!

done! :)

okay. back to try this one again