Sudoku Puzzles

Am l first?

sweet baby
looks like I'm second - or close to it.
good Maen all

Good Maen to all! Puzzle took me forever, but worth to see the Easter egg hunt photo! Guess I'll boil some eggs for lunch!!

Have an excellent Maen, all.

10:02 2 guesses

I liked this one!

Alene, I will be in Spokane next week! VACATION!!

nice pic..cute baby in pink frock and pink ribbon with bow on the little head...and regarding the puzzle had some hiccups initially and continued to solve with ease only to get stuck again..sort of tricky i felt..anyway finished it..
cheers

3rd but very slow with guesses 23.41

looks like everyone else got on while I was slogging away

AAAAARGH!!!!! Forgot to set the timer!!!!! But it was a good honest completion in what felt like a reasonable (shortish) time. Probably a sub 15 min, which is ok for lil' old me....

A relatively simple puzzle today:

1) Start 22, Unique Possibilities to (UP) 25.
2) Hidden pair 68 at gi9 forbids g9=1, i9=145, g8=6, i78=6. UP 27.
3) c1=1 == c9=1 -- a7=1 == i7=1 -- i45=1 == g4=1 forbids g1=1. UP 44.
4) Hidden pair 68 at i29 forbids i2=479. UP 47.
5) c6=5 == More...

the pink one goes with my dress, mummy.

Hi Pat -
You asked several days ago - sorry I have not been able to sud. for a bit - about how I use forbidding chains. I have modified the original use of forbidding chains to a more general usage:

A == B means A OR B.
A -- B means (notA) OR (notB)
A, B are boolean More...

To further complicate matters, I also - quite validly - will use any strong subsets inside of a chain to forbid whatever they forbid, whether they be endpoints of that particular chain or not. I will look at the specific example you talk about later - it is possible that I erred, as I often typo More...

Pat - I think Clark explained that day -
The chain could read:
b5=2 == X wing at d7f7,f4d4 - (shortened a tad)
Then clearly, b5 == (one of f7,f4) must occur.
This generates the extra forbidding (f5 I think?)

6:22 with several guesses to get going.

And Steve, you could add that even when you understand all of the boolean logic, it needs a very good eye to spot a lot of these chains. The ones that work with only one number are pretty easy, but as soon as multiple numbers are involved it gets difficult to see them.

Even using matrices, first you have to spot the chain.

But then there were also people who could do a Rubrik cube without thinking in a few seconds.
There are people here who can solve the most difficult ones in a couple of minutes without knowing how ... savants, I think they call them.

I like working through a tough sudoku and get a reward of seeing my daughter. Lots of fun.

Good mAen, all!

Steve,
When you say:
A == B means A OR B.
A -- B means (notA) OR (notB)

Do you mean to say?:
A == B means A OR B must be True.
A -- B means (notA) OR (notB) must evaluate to True.

Of the 4 boolean states for 2 variables, FF, FT, TF, TT. The == links are easy to More...

logged in to do yesterdays puzzle and stopped on the way to read the comments. It's definitely all way beyond me. I guess I'll keep guessing and occasionally get lucky!

Jeff - in technical terms, == means at least one or both is true.
-- means at least one or both is false.

The logical OR statement is precise in my usage above.

Although, on the grid, it is true that usually native strong (==) links are also weak (--), that relationship is not More...

It is a common misconception when using forbidding chains to think that A==B means exactly one is true. This is not the case. It means that one of these states: TT,TF,FT exists, is in your example.
A--B means that one of these states exists:
FF,FT,TF.
One can argue, of course, that on More...

The reason we call them forbidding chains is that the -- (weak) links we call forbidding links.

A -- B means A forbids B (order is not important, so also: B forbids A). The only excluded state is that A,B are both true.

A == B (strong link). Only excluded state is that A,B are More...

Cute picture!

Hi Steve from Ohio

Do I have a misunderstanding of forbidding chains here?

My understanding of a strong link is:
A==B If A is not true, then B must be true and vice versa. So a direct link where one possible must be true. This usually happens where there are only 2 possibles in More...

Steve
I just saw your latest input. Will read that first.

OK, gotcha, If A is not true then B must be true, and vice versa, does not rule out that both are true, even if it usually means this. So a true OR function.
And for the weak link also a nice (not A) OR (not B)

Great to have helpful people to explain your own problems and answers.

Steve,
I have wracked my brain, but cannot think of any place where A==B and both can be true. Can you give me an example?

to Steve and others adepts at forbidding chains.

My main interest here is not to write a computer
algorithm to find fantastically gnarled chains but rather to produce an interface (filters, various masking tricks etc.) which facilitate a user search for elegant forbidding chains, without More...

Hi John - native strong links are always weak. Implied strong links are not always weak. Example:
today's puzzle, my step 3 to come.....

Hi Pat, I am doing something similar.
Only tough makes a challenge, and it is difficult to do something without making the whole thing too easy ... that is what I found.

Hi pat!

I am not sure that I am qualified to explain this:
The overlapping of strong links clues me into where to look - much as JRD's double chain method looks for many results forced in both directions. - Add to that overlapping the knowledge that some overlappings might also force More...

Much like Clark's:
1) Start at 22 filled - the given puzzle. Unique Possibilities to 25 filled. (UP 25).
2) Hidden pair 68 at gi9 forbids g9=1, i9=145, gi8=6,i7=6. UP 27.
3) fc on 1's: c1== c9 -- h9 == h13 forbids g1=1 UP 44
4) i7=1 == a7=1 -- a9=1 == a9=5 -- a6=5 == i6=5 -- i6=2 == More...

Sorry should have written alternate step 4 this way:
g1=8 == unique rectangle 68 at gi29 forbids g1=29 UP 81

Depth of the alternate step, if one allows this logic - it presumes not more than one solution - is 4. rating would go down by .03, sets down by 2.

Definition of a term:
Native link - a weak or strong link specified by the rules of the game.
Implied or non-native link - a weak or strong link derived by a forbidding chain - or some other sort of logic.

I'm one of those who don't 'get' how I solve the toughs. Sometimes I do follow your proofs, but to be honest, I don't really get them all, and don't really get much satisfaction in following someone else's way of doing it. I REALLY admire the fact that not only do you solve the puzzles, but you also keep track of how you do it!!