Alfred from Sydney

Hello Alfred - I just saw your test comment on tough so thought I'd drop in and welcome you to our crazy world of sudoku.
Just leaving some so that you can decorate your place for your visitors. Some photos would be nice!
Also leaving a six pack of Crownies for you to share with your visitors.

testing...testing...
Yep.. there is a crazy world out here..called sudokuland...
Anne is very generous... commonly known as 'Queen Anne'... very old joke..
You will us a very chatty bunch and it would appear that we have nothing better to do than spend the day 'visiting'.... it is a great way of getting to know everybody so join in..post often.. get to know us as we get to know you. ENJOY..

WELCOME Alfred
I live about 5 hours north of you.
Have fun on this site.

Welcome to the puzzler group. I hope you enjoy them as much as the rest of us.

Alfred, good to see another Sydneysider join the sudoku family. Enjoy the puzzles chat and friendships.

Glad to have you join us. May all your days with us be good ones.

Alfred you have been taged.

Thanks, Alfred. Looks like you just joined, too. I just posted a specific response to your help on today's Tough, so I won't repeat myself. Just didn't want you to miss the big

I intended to end with a thank you smilie and I hit the send button instead.

Hey Alfred, thanx for posting your proofs in plain English. It all makes sense now

What was it that caused both you and Clark to concentrate on 3 in the Tough today? In retrospect it's obvious, but there were other numbers that were "either/or"s. Did you check out all or several of them until you picked up on the 3 or was there some other clue that it would be the key? I'm asking Clark this also.

Alfred, I couldn't find your comment. Now I am curious. can you repost it on my page?

silly me! I was looking through today's comments instead of yesterday's. Thanks for the idea. One day I might get myself organized to be systematic and to bring my haphazard brain under control.

Alfred, What I wanted was a chain that would eliminate 4 from d1. If that candidate is eliminated then there are locked candidates for 4 in box 8 that eliminate the other 4's in column 6 and the entire puzzle unlocks using only basic techniques after that(it might even be unique possibilities to the end but I don't remember for sure). I find it interesting when the elimination of a single candidate unlocks an entire puzzle, and I knew that candidate would do it but I could only remove it after two chains but I have the feeling it could be done in one.

Alfred, I don't see any typos on my July fourth post. If you still think that you see some I'd be happy to look at them and post a correction.

Thanks for the message, Alfred. This was a joke started a few weeks ago by one of your own (I forget whom exactly). I have MAJOR dyslexia with numbers and wouldn't be able to follow that stuff even IF I understood it.

Hi Alfred,thanks for the message about the numbering...I think I understand it better, although I am afraid the chess analogy was lost on me since I don't play-- have never been able to figure it out!! but the message did make more sense after you explained it-- I am not sure what logic I use to figure out the puzzles, but I certainly don't think I am that analytical about them!! Hope you are having a good day/night today, talk to you soon

Alfred, I had a feeling I couldn't manage a post that long without typos. I'm sure there are shorter more elegant proofs but I'm also sure they are beyond me for now. Thanks for writing.

Thanks for the message Alfred. My proofs are so much less efficient than ttt and sotir that I try to only post the steps that are absolutely necessary to establish my chains. I left out several eliminations that I found but which were not necessary for my proof. I even leave out simple locked candidates and naked/hidden pairs/triples/etc. in the interest of brevity. I wish I knew how ttt and sotir find single chains that totally unlock a puzzle, it almost always takes me at least 3 beyond basic techniques. Anyway, always a pleasure hearing from you.
Regards,
Jeff

Hi Alfred

We agree a4=39 and a6=49

In the ghi-456 box, the following hold
- 3 is at h5 or i4
- 9 is at h5 or h6

So, if a4=3 then i4 is not 3 then h5=3 then h6=9 then a6=4

And if a4=9, then a6=4.
So a6=4 either way.

then follows i6=8, i4=3, a4=3, a1=9 ... and UP 44.

Cheers

Alfred--I just went back through and re-solved 9/21 tough up to 43 squares. There are definitely a few hot spots where I got stuck, even though I was doing it for the second time. The thing that got me over the worst hump was finding a 46 hidden pair in row5 that removed 8 from 4H, thus allowing 5G&H to claim 8 for row 5. This removed 8 from 5D&F, which was a big help!

Also, I did more research and realized that my XY-Wing is wrong! Once again, I'm the victim of a serendipitous accident. Thank you for pointing this out and encouraging me to look deeper. I'm just beginning to learn to apply the advanced strategies, and my book doesn't describe how the pairs must be arranged regarding areas. I checked a few websites and learned that my XY-Wing would have had to have 2 pairs in the same box to be valid. If the 3 pairs are in different boxes, XZ and YZ must be related to XY by a row and a column (one each), forming a triangle. I guess it's back to the drawing board. Thanks again, Alfred!

For me, forcing moves and following chains are quite difficult. I'm much better at finding patterns in the numbers -- then I go back and read the theory of why the patterns work. I'm always amazed an how many ways there are to approach these puzzles. :-) VAL

Hey, Alfred -- Yep, I definitely meant G, not H. The lack of consistency in row/column labeling is very confusing. Some sites number rows top-down, others bottom-up. Some sites even use letters for rows and numbers for columns. Such a puzzlement!

As for today's (well, yesterday's for you) puzzle, I did indeed mean G, not H. I solved to 40 using basic methods. Then, since I'm not so good at forcing chains, I used a different kind of logic to eliminate pair possibilities in column G without looking outside the column. It took me a long time to find an area where the eliminated possibilities would give me useful data, but better that than the dreaded chaining!! :-)

The pair exclusion forces candidate elimination in one area (in this case, G). I listed the possible values for the triple 1/2(G8), 2/5(G4) (1/2, 1/5, and 2/5). Any 2 squares in the same area as a two square triple cannot hold any of that triple's possible pairs or they would create duplicate values in the same area. So I took two squares in the same column as my triple pair (G7&G5) and listed all of the possible pair combinations for those two squares.

Then I eliminated the pairs from the triple, and presto, I was able to eliminate several pairs as impossible due to redundancy. That left me with 1/4 and 2/5 as the only viable possibilities for G7&G5. Since 25 already exists in G4, I was left with G7=1, G5=4.

And I thanked my heavenly stars that I could crack it without chaining. Your beautiful proofs scare the bejeebers out of me. It'll be awhile before I train myself to force chains, or use colors to crack a puzzle. Till then, I'm gonna have to get creative to compensate for my handicap.

Hi Alfred,

The "U" in AUR has always stood for "unique", because it is taking advantage of the requirement that a sudoku have only one solution.

You're welcome.
Terry

Alfred and family! Thanks for all your proofs of the Tough from time to time! Most helpful!

Nice to meeting you and Margaret yesterday!

Arrgh!

Nice to meet you ...

or

Nice meeting you!

Early night tonight I think!

I'm hoping you receive this comment because I think you asked me not to send email.

Please, I'm stuck right off the bat. You mentioned cell i9 (May 1st Tough puzzle) is a 3. If the numbers go from top to bottom, wouldn't the cell reference be i1 versus i9? I really really want to (need to) understand how to solve "tough" puzzles. The "hard" puzzles are ALL easy compared to the tough ones.

Thank you and please don't feel like you need to reply immediately (especially if you're busy).

Kind regards,
Janice

Thanks Alfred!!!

I'll give her another go (I'm sorry because I probably didn't read it right the first time).

Hi Alfred,

If you have time, I put a picture of where I'm stuck with the 5 6 2009 tough puzzle on my page. Please glance at it if you get a chance. Maybe you can see where I'm going wrong.

If you don't have time, I completely understand.

Take care,
Janice

Alfred..I'm tagging you on the easy page. I hope you will take part as I know little about you. Cheers.

Hi Alfred! I hope you're having a pleasant break. I miss your diagnoses on the Tough!

In that case I am also looking forward to some GREAT pictures on the Tough (which, incidentally, come up first on the Easy Jigsaw). P.S. Welcome back

Hi Alfred,

I reset the possibilities at 42 and round that the unique possibilities kept growing til there were only about a dozen numbers to fill. Perhaps I made a mistake.

Thank you so much for the understandable explanation. After that, the whole puzzle fell in place! I knew it would-I just couldn't get that first move. Thanks for taking the time to explain to me. It just seemed like there was such a great jump from the hard puzzles to the tough.

Thanks again, Alfred !

A. I don’t see the typo in 2a in my draft (but see below). I no longer have access to what was actually sent you, but I did see the message you sent me explaining your question. Sorry about missing it before.

B. Sorry, I left out a5=9 after f5=7. So mine would go to a7=6. However, your way would shorten the chain.

C. I apologize again. At the last minute, in sending the message to you, for brevity I deleted part of the full chain of i5=6 to just go to the h3=6 or 9. The deletion may have caused the typo you see. I forgot that some of the full chain cancellations were to be needed. The full chain (as far as it goes, and it’s not long) is – if i5=6, d5=1, h5=2, i3=2, h6=1, e8=1, d8=3, e4=3, e3=5 & h3=6 or 9. With the full chain for i5=6, c4 is the only 6 left in row 4 after d4=9.

Sorry again, in the part of the full chain I deleted (see above), i5=6 makes e3=5 already. If your way comes out shorter, that’s OK, too, but then again you’d have to leave out part of the full i5=6 chain and that might change other subsequent stuff.

D. Yeah, and, with that end in mind, it looks like the chain can be shortened by 3 or 4.

Absolutely go forward with the post as you say, however you may think it best to include or not the above information.

NOW, . . I also have a “lesser mortal” solution to Sep 2. Would you like, or be willing, to look at that before I post it?

Regards,
Brenda

Hi Alfred, re yesterday's tough, I haven't gone back to double check that I had all the right possibilities but had saved the puzzle just at the stage before the chain began and by my calulations f9=8 prevents d7 from =8... I dod tend to be a bit careless so could easily have stuffed up ... and today is a brand new puzzle.... You say it's easy. I'm just home from a night out and about to give it ago before bed. Cheers.. and thanks for your comments and solutions.

We've been cross messaging ... probably better than cross dressing but confusing all the same. OK GOOD! I don't have to go back and redo the puzzle .. Thanks for that.

Wishing you and your family a very Merry Christmas



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