Tough Sudoku

Hell, I hope that's the photo on a lean and not me. I'm sure I've only had about 4 glasses or so of wine.

9:54 not that hard today, just seemed to take a long time.

well,i never had a single sip of whatever anne is having,still the pic looks leaning....so its the pic and not the viewer,having 'lean'problem!!
cheers

and to my friends here in tough,i wish a
MERRY CHRISTMAS
AND
A HAPPY NEW YEAR...
i am taking a flight after midnight tomorrow to US.Joining my son in Boston and will stay with him for a couple of weeks..so bye from me for this year...
will catch up as soon as i can have an access to a pc..
cheers

Bye ap, have a lovely holiday.
Where are these markets?

10:45 morning

he was being creative Anne ;)

16:25

beautifully symmetrical today, a lovely puzzle composed masterfully and a pleasure to solve.

YIPPPPPEEEEE!!!!!!!I can NEVER get through the 'toughs'

That's a different slant on things!!. Sure wish I could grow those beautiful flowers in my backyard.

Merry Christmas all.
ap, have a safe journey and a wonderful visit;
anne, have another glass of wine, you don't need any sleep.

Markets in NT are going down-hill? fi.

Bird of Paradise?

I can't seem to get through the Tough ones and I am pretty good at deductive reasoning. I've read the advanced strategies but don't find them applicable to most of the puzzles. Invariable i get stuck in the early running (and don't want to guess). Is there anyway to send someone what I ahve saved so they can point out a next step?

15:02 with one guess. Cs, I made it a long way before I had to guess in this puzzle, but still I get to the point where I just don't see any way to eliminate any more. Anyway, don't think I'd be much help. I am getting better about my guesses, though.

Hi Cs from usa!

Eventually, the blog at this site - the link is in the upper right corner - will deal with advanced strategies that do work on most, if not all, of the tough puzzles from this site. Please be patient as it will take a while to get to those types of strategies - but if you are good at deductive reasoning, the techniques I will eventually expose should be right up your alley.

Good afternoon to all! Thanks for sharing this picture with us Fi!

steve, i'll be looking forward to that blog. i too get stuck and have trouble understanding your proofs. I finish about 1 in 7 on tough, but i did finish today! merry christmas!

A proof for not very tough sudoku of 12 23 06:
1) Start at 23 filled - the given puzzle. Unique Possibilities to 27 filled. (UP 27).
2) Locked 5's t c12 forbids c45=5 UP 30
3) Hidden pair 58 at h12 forbids g12=8, h1=126,h2=26 UP 48
4) Pair 16 at c35 forbids c149=1 and forbids c1249=6 UP 55
5) fc on 1's: d8 == f9 -- g9 == g3 -- c3 == a1 forbids a8=1 UP 81
Sets: 1+2+2+3=8. Max depth 3 at simple coloring step 5. Rating: .14

Today's puzzle unravels using some things already covered in the blog, pluz one technique not yet covered. Locked candidates, hidden pair and naked pair have already been covered. Coloring, however, will be covered in the first blog after Christmas. Today's puzzle solves easily using coloring. Do not be discouraged by my shorthand notation above - that will eventually also be explained. I may use today's puzzle as an example in coloring.

Best of the season to all!

Step 5 in my proof above decoded - with some clumsy notation:
For this decoding,
=> means implies
<> means does not equal.

Note the following:
1's in box e8 are limited to two locations:d8,f9
1's in column g are limited to two locations: g9,g3
1's in box b2 are limited to two locations:c3,a1

d8=1 => a8<>1 but
d8<>1 => f9=1 => g9<>1 => g3=1 => c3<>1 => a1=1 => a8<>1

Thus, whether d8=1 or d8<>1, a8 cannot be 1.

BTW- When I first starting visiting this site - almost exactly one year ago, I could not understand gb's proofs at all.

I struggled with the puzzles using my own clumsy logic for some time, and just sort of breezed over gb's elegant proofs.

When I finally broke down and tried to really understand what he was doing - a whole new chapter in solving these puzzles began to open for me. So...

When people note that they do not follow my proofs, I think I know exactly what they mean - 'cause it all seemed like so much goobly gook to me also!

This is a different view. Nice picture of a sunny day at the market.

23:39 - with a moderate amount of guesses! Merry Christmas to all and to all a good night.

21:50 First time I ever finished a tough without guessing. Probably an unusually easy tough? When I get a chance, I will work on understanding the information in the Blog. Thanks Steve.

Mary, Parap Markets are in Darwin - about 3 blocks from where I live. It's a great place to go for breakfast on a Saturday with lots of tropical and Asian food tastes available from laksas to satays to fruit drinks and icecreams, pacific island sweets etc - There used to be a bloke who took the top off coconuts and put a couple of straws in them but that stopped years ago - PITY. There are also (as you can see lots of arts,craft and vegi stalls- then bu mid afternoon- you would never know that it had been there. Wakka came up from Brisbane for my birthday in October. As you can see- all the excitement made him quite dizzy.- or was it the laksa.

STEVE:
Another solution (with a little less finess - but then what would you expect from me ;)

At 23 filled – up to 29 whilst setting up ( c7& d9=7, e7=8, g5 & i8=5, d9,h3& i9=2)

At 29 filled, e4 & e6<>5 because in 3 steps from either Cb would have 4 cells with only the possibilities of 168 in them therefore :. e9=5

Fill up to 40 (knock off your 2s, an 8 and then some 4s and a 9)
then look for some hidden pairs.
i6 <>4 because == i2=6, c2=5 leaving f2&h2=8. In the same way i4<>4.

Knock off the rest of your 4s and a 3. Up to 44 filled.
But then check the locked 7s in Bh5- Up to 47

Ic5<>6 because=> d5=1, =>d8=9, =>f9=1, =>g9=6, leaving both c3 &g3=1 :. C5=1

Puzzle unravels to 81,

Have a cool yule every one!

Step 3: Is there really a 'Hidden pair 58' at h12? I see 5's other places within the box, rows and column. Thanks.

Nevermind. I've got it now--The pair 16 solved everything. Sorry.

Nov. 5, 2007.

SE=2.6