dailysudoku.com

[guest]

Hi there,
I try to solve a sudoku in our local newspaper but have problems. I know right now these numbers:

9 - 3 1 - 5 7 5 6
- - - - - 4 1 - 5
1 - - 7 - 6 - 8 3
2 1 8 - 4 3 - - 7
5 7 - - - 8 3 1 4
3 - - 5 7 1 8 - 2
8 3 - 4 1 2 - - 9
4 - - 8 - 7 - - 1
- - 1 - - 9 4 - 8

Any idea how to continue?

[tushar]

first row cannot have two 5

[Guest]

[someone_somewhere]

Hi,

This one (after correction) looks very, very hard.
I could not find anything with the standard methods.
Has anyone tried Swordfish, XY-wing, Coloring, etc on it?

see u,

[modulated]

The Drawer reports that this is an invalid puzzle (i.e., no unique solution solvable by logic -- requires guessing or trial and error).

[someone_somewhere]

Hi,

Correction the Draw does NOT report that it is IMPOSSIBLE.
It reports that it COULD be impossible.

At least this is how I read the very long message it is issuing!

see u,

[someone_somewhere]

In other words, the DRAWER is as smart as we are for that position.
We can only to try to be better.

see u,

[guest]

Hi there,
now there was the solution of this sudoku in our newspaper. But I do not know how to get to the solution from the point showed you above.

9 2 3 1 8 5 7 4 6
6 8 7 2 3 4 1 9 5
1 5 4 7 9 6 2 8 3
2 1 8 6 4 3 9 5 7
5 7 6 9 2 8 3 1 4
3 4 9 5 7 1 8 6 2
8 3 5 4 1 2 6 7 9
4 9 2 8 6 7 5 3 1
7 6 1 3 5 9 4 2 8

[someone_somewhere]

Hi,

You could imporve your technique from:

http://www.simes.clara.co.uk/programs/sudokutechniques.htm

But, . . . the for the one you have posted, you will have to try Swordfish, Coloring, XY-wing, Forcing Chains, Nishio, or (let's hope not Trial and Error) ...
not even X-wing will help you!

Have fun,
see u

[Kiwi]

1. Pencil in possibilities
2. Take a pair (best choose a pair where it occurs in several places) eg ( 6,9) in r6,col 8
3. Now assume the 6 to be the correct one.
4 Quickly follow thru the whole puzzle using this assumption until you reach a dead end or it comes out.
5 If you reach a dead end it obviously must be the other one (9) and follow that thru instead.
6 Hey presto - prob solved!!

cheers from down under

[someone_somewhere]

Hi,
What you are describing, is the "Trail and Error" and it should be applied when anything else did not work!!!

Keep it mind that when you are applying this method to early, you will have to make a second assumtion, and maybe this will not be enough, and you will have to use Araine wire not to get lost in the labyrinth.

Have fun & see u,

[someone_somewhere]

When you do it "not too deep" it is called also "Nishio".
This you can do without any pencil !!!

[Kiwi]

I did say when all else fails!!!!

[David Bryant]

[squirrel]

There are also hidden pairs {4,5} in r3c2 and r3c3.

After finding these I went looking for forced chains of 1, 2, etc. Fortunately I never got to "etc" because 2 had only one possible solution. After this, everything else fell into place pretty easily.

Got lucky with this one.

[David Bryant]

After reading some stuff on other web sites, I realize that the technique I described in my previous post is called Nishio, an eponymic honor to a renowned Japanese player.

Here's a good resource if you want to understand this technique: rubylips.

dcb

[Milan]

When you run out of obvious moves, look for where there are a pair in the same row. Save your moves up to that point and take a guess and pick one number of the pair, leaving the other number in the other square. Play it out and if you run into a problem, then go back and reverse your two picks. it worked for me on your puzzle.

[Milan]

When you run out of obvious moves, look for where there are a "matching" pair in the same row. Sorry for omitting that in my first reply.

[Guest]

This puzzle has multiple solution.
One other solution is

9 2 3 1 8 5 7 4 6
6 8 7 3 9 4 1 2 5
1 4 5 7 2 6 9 8 3
2 1 8 9 4 3 6 5 7
5 7 9 2 6 8 3 1 4
3 6 4 5 7 1 8 9 2
8 3 6 4 1 2 5 7 9
4 9 5 8 3 7 2 6 1
7 2 1 6 5 9 4 3 8

[chobans]

Column 2 has two 2s on your solution. And column 3 has two 5s on your solution. So that's not correct.