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Tough Sudoku for 15/December/2005


Choose a number, and place it in the grid above.

  1 2 3 4 5 6 7 8 9
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Sudoku Solving Techniques

Submitted by: sudoku lover

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It's good to be the first to finish a Sudoku.
Oh fi! My neutron flow must be in reverse thrust!
Be back later to work puzzle
Didn't we see that little ant hill the other day?
It's getting late & I have to write out my Christmas cards to send. So, Goodnight, all.
didn't time myself (got distracted by the little one too many times!) but it wasn't that bad
07:12 whoops!!!!!!with little help.started with 3sgot stuck at 5.allowed chec moves.mmmmmm then free flow.ok able to finish.
nice shot of the pyramid.
what is ever body doing to day i so f**** bored to day there is not any thing to do
Anyone have tips on how to do these faster? Right now I'm basically putting each possible number in each square and eliminating from there. But that takes about 30 min!
Dan: Don't despair. If you want to do it really fast, just turn off the button that says 'allow incorrect moves'. Then use trial and error; if you make a mistake the box will blink. Of course, this is not logical deduction. Your way is the legitimate way; don't worry about the long times.
pretty easy today, basic eliminations for the most part.
Dan, I think it's better and easier to do it this way. Instead of going box by box and putting in all the numbers in one box at a time, go number by number and put that number in all the boxes it can go in. This way, you can fill in somethings and make some eliminations as you go.
Where has jb from f disapeared to???
I basically do the same thing.....but with time, you will be able to do it faster
Dan listen to Howard
I started off great, then got stuck! I ended up finally guessing incorrectly which I used to my advantage.

Dan, I go from 1 to 9 and it still took me 24:19 since I got stuck.
Yvette, am I jb ? If so, I'm rather busy just at the moment... Fortunately splendid solvers now offer their solutions here, which delights me most. Despite all this, here are cryptic hints for the nostalgics...
1) easy to 26 filled.
2) Looking at 9 in Bb8, at 1 in Bb8, at 7 in Be5, at 37 in i4i8, at 59 in f2f3, eliminate some possibles, then easy to 39 filled.
3) Looking at 25 in h8h9, at 15 in a7a8, eliminate some possibles, then easy to 54 filled.
4) Looking at c5, eliminate b9=4 (beware, heptagon). Then easy to unique solution.

And full details in sandbox...
difficult,several times used guesses!
Sorry gb missed you today love reading but not understanding your comments. One day i will i promise
Starting at 28 filled: c1=3 c8=6 d2=3 d3=6 e1=7 e2=1 f1=8
pair 25 in col.e e6=6 e8=9
pair 59 in col.f f7=4
remove 1 in Bb2, 4 in Bh2
triple 347 in Bh8
remove 2 in col.h
chain 257/57/27 in row 5
whathever you choose in b1 (5 or 6) leads to i1=4
pair 37 in col.i
remove 2 in col.g, 8 in col.h
pair 25 in Bh8 i7=8 d9=8
pair 25 in row 9
pair 15 in col.a and easy to 55 filled
In Bb8, Bb5 the chain 49/49/41/19 leads to b9=9
easy to the end
Sorry Gb, I didn't know you were there (busy with my thinking and writing, didn't refresh the screen).
I had to do your job yesterday!
Valy, now I rely on you and other brilliant solvers to keep up the good work here because I may be less present for a while...
Dan from Texas- I start by doing all the numbers in the boxes where the numbers meet at right angles i.e. if there is a 1 in a1 and i9 I fill in all the places where a 1 can go in boxes Bb8 and Bh2. Then I do the same with the 2s and so on. This leads to a lot of eliminations and possibilities More...
Woops! It put both my names in- forget that! After the first stage I pick a good looking box or row or column or group of three boxes- i.e. the boxes across the top- and work on those. It helps reduce the elimination work- and it's more fun!
17:56 Easy peasy!!I suspect the pic may be of something in Egypt!
Finally! All logic but slow. And all our snow melted today! Bad timing for Christmas.
I got 06:31
Question....Do you reach a point when 'deductive reasoning' goes no further, and 'guessing' becomes the only way ????
Not guessing, but following two mutually-exclusive possibilities to the point where they both lead to the same elimination....a very sophisticated form of trial and error. The problem is to spot the pathways.....not easy (for me)
Sorry, got the address the wrong way around - I was writing Jack, not Jack writing me!
31 filled and monumentally stuck!
I was afraid you were going to say that...Almost like solving problem by arriving at answer so that question becomes obvious.... -:)(
Thanks for response Christina
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