Sudoku Puzzles

4pm here in Spain just looked in to see if anyone had started. Too hot now to do puzzle but I am first to comment! A first.

Snack time! Good Maen, all. Stay dry if you live in the NE USA.

11:34 Maen

Maen. Can't believe I am second...a first for me! Love the suspension look of the pic.

Hello, Fran, in sunny Spain. I'd complain about the rain here, but we need it. Have a great day/night, everyone.

Another old repeated picture! **yawn**

I must be really off today, could not figure out this puzzle AT ALL. A real head scratcher here.

06:44 v ery easy

To Fran in Spain - it's 2am here and a very cold Winter. Be careful not to overheat your computer - it might crash! G'day all. I'll tell my time for Tough level when it becomes respectable - could take awhile. :)

Not too hard today

Probably improvable:
1) UP to 26.
2) h23=1 forbids i3=1; UP to 28.
3) a67=3, e67=3 forbids df6cd7=3; d7=8 to 29.
4) i79=6 forbids i34=6.
5) f23=8 forbids f456=8.
6) Triangular Matrix
i3=2 i3=8
0000 f3=8 f3=6
0000 0000 f1=6 f1=9
f4=2 0000 f4=6 f4=9 forbids i4=2; UP to 48.
7) b45=67 forbids b279=67; UP to end.

Too Easy!

38:06..with help from Andrei. Others saying the puzzle was easy.. I must have missed something.

That picture makes me want to invest in a good bb gun.

13.11 Steve from San Diego- we reserve our bb's for the d*m* squirrels that raid the birdfeeders.

9:33... nifty photo! good mAen all.

15.06 with a couple of guesses. Cooled down a bit now. Wouldn't mind a bit of that rain, Cathy but we won't get any serious stuff for 2 months now. I'll stop now so I don't overheat the brain either.

STEVE FROM SD: You shoot innocent little birds?? Stay outta my neighborhood!

My proof, developed independently of Andrei's

1) Start 23, Unique Possibilities (UP) to 26.
2) Hidden pair 16 at i79 forbids i7=58, i9=58, i3=16, i4=6. UP 29.
3) f3=6 -- f4=6, and f3=6 -- f1=6 == f1=9 -- f4=9, so f3=6 -- f4=69 == f4=28. i4=2 -- i3=2 == i3=8 -- f3=8 == f3=6, so i4=2 More...

1)Start at 23. Up to 26 (f8, g9, i1, g9).
2)Pair i79=16 and bc2=1 -> h3=1, up to 28 (h3, i8).
3)Pairs gh8=48 and cd8=23 -> b8=9, up to 29 (b8).
4)Pair a6c5=38 -> c12=7 -> e3=7, up to 30 (e3).
5)if e4=8 -> i4=2 -> i3=8 -> pair f13=69 -> f4=2 so e4<>8 -> More...

Clark: I have trouble understanding your reasoning in step 3).

Andrei,

My step 3 is one that should be written as a matrix. Here is what should be the proper matrix:

i4=8 i4=2
0000 i3=2 i3=8
0000 0000 f3=8 f3=6
0000 0000 0000 f1=6 f1=9
f4=8 f4=2 0000 f4=6 f4=9

This gives us i4=8 == f4=8 which forbids 8s in the rest of row 4.

Clark, if you remove the first row and column from your matrix, you get precisely the one from my step 6). So your solution is very close to mine but seems to be slightly more complicated (depth 5 instead of 4).

Clark, I should've said that reducing depth to 4 comes at a price of killing f4=8 first (this is why I needed more preceding steps). So this is really a trade-off.

Hi Andrei, Clark, etc!

Very late looking at today's puzzle. I have a depth 4 solution, but it involves two depth 4 steps so it is not nearly as good as Andrei's.
Andrei's proof looks to be the most efficient. Can use only the locked 7's in his last step to get to up81, so Andrei's More...

Huaiyu From Paris: post under Sudoku techniques so the rest of us can avoid twaddle

Just for the heck of it, my grossly inferior proof:
1) Start at 23 filled - the given puzzle. Unique Possibilities to 26. (UP 26).
2) Hidden pair 16 at i79 forbids i3=1, i34=6, i79=58. UP 29.
3) a6=3 == a7=3 -- e7=3 == e6=3 forbids cd7=3 and df6=3. UP 30.
4) f5=3 == f2=3 -- f2=8 == More...

hmmm typo in my proof:
4) f5=3 == f2=3 -- f2=8 == f3=8 -- i3=8 == i4=8 -- e4=8 == e6=8 forbids e6=3 and forbids f456=8.

sorry!

9:30 For another repeat!!! Please, everyone send in new photos!

Sorry. It's a great photo. It's just that I've seen this hummer at least 4 times.

C'mon everybody! Submit more pictures for the Tough!

Hi Huaiyu!
Your solution appears very similar to Clark's solution, except that your very deep step 6 could be eliminated: If you look carefully at your chain in your step 5, you may notice that you could have forbade 8 from more locations in row 5, which would have made your step 6 unneeded. More...

just one guess between 4 & 9 in the bottom middle square then all unfolded. what maths could have saved me from guess?

27:33 slow today...
new photos definitely needed, these have all been repeats for the last week!

29:34 but at least its all my own deduction. Refused to give in to impulse to guess.

Does anybody do this just for fun or do you all take it so serious? Who cares what the photo is.

16:38

Aug. 6, 2007.

SE=7.2