dailysudoku.com

[hollydoll]

Where do I go from here? Thanks.

8xx x57 xxx
x3x x4x xx2
xx6 x21 xx5

1xx 78x 59x
xx9 2x4 8xx
x8x x95 x23

4xx 57x 2xx
2xx x6x x5x
xxx 4x2 xx7

[Guest]

You can place a 4 in square 3 (but I wont tell you where).
Then you can place an 8 in square 7.
After that, I'm stuck too. I know what the next hint is, but I can't see why.
Anyone tell me?

[chobans]

After you place 8 in box 7 (r7c1-r9c3) at r9c3, if you notice, in column 3, 5 can't go anywhere else except at r2c3. After you place 5 there, it'll eliminate the possibility of 5 at r2c1, leaving only 7 and 9 as possibilities. These are the same two numbers that's possible at r3c1. So you can eliminate 7 and 9 from the other cells in box 1 (r1c1-r3c3), meaning r3c2 can only be a 4.

Let me know if this isn't enough to solve from here.

[Hollydoll]

How do you know where to put an 8 in the 7th box? And as far as where the 4 goes in the third box - I don't get that either. More help is needed. Thanks

[someone_somewhere]

Hi Hollydoll,

You have to learn and use the techniques:
"Column on 3x3 Block interaction"
"Row on 3x3 Block interaction"
"3x3 Block on Row/Column interaction"

you can take a look at:

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

for this.

Than there will be no more problems to solve it.
Or, you will have to work it out by yourself (the hard way).

If you would like a particular help for this Sudoku (that other participants have also refused till now), we can provide it. Please, just tell us.

P.S. I know that you can do it!!!

see u,

[David Bryant]

[Bruno]

[David Bryant]

There's a good discussion of "swordfish" under the Other Puzzles category in this forum, right here.

Briefly, the Swordfish works by identifying 3 (or more) rows or columns in which a particular value can only appear in two cells. We then get a connected loop of {n or ~n} pairs. We may not know which state the loop is in, but we can be sure that it is in one of two states, and that fact may help us to make inferences about the rest of the puzzle.

I'll post another message later, with an example. Be sure to check out the link above -- it will help you understand. dcb

[Bruno]

Thank you for the link and the sumary of the explication
now i understand the "loop" technique

I'll check your example later !

[Guest]

Hi,

It's me again.
He a very nice and abstract description of several very advanced techniques, that I found:

Look for N columns (2 for X-wing, 3 for the Swordfish, 4 for a Jellyfish, 5 for a Squirmbag) with only two candidate cells for ONE given digit. If these fall on exactly N common rows, and each of those rows has at least 2 candidate cells, then all N rows can be cleared of that digit (except in the defining cells!).

I am still learning, ....
see u,

[someone_somewhere]

Previous mesage was from me,
someone_somewhere.

I just was under deep cover ...

see u,

P.S. for the ones from you that know japoneze:
I am "inbijiburu" and you can reach me at inbijiburu@gmail.com

P.P.S. please no japooneze emails.

[Going Mad...]

Doing this and now stuck. The hint says the number 6 in Box 4 but can't see why that the next logical step after doing number 4 in Box 3. Can anyone help explain please?

[someone_somewhere]

give us your exact position in the universe, so we can guide you ...

it's hard to imagine at what coordinates you are stucked pilot.

SOS without any additional information will not bring help to you.

see u,

[Going Mad]

Sorry! Ok - here we go...

8xx x57 x4x
x35 x4x xx2
x46 x21 xx5

1xx 78x 59x
xx9 2x4 8xx
x8x x95 x23

4xx 57x 2xx
2xx x6x x5x
xx8 4x2 xx7

According to the hint, it's 6 in r6c1 - but I can't figure out why!

Thanks!!! It's been driving me mad for hours!

[David Bryant]

Hi, Holly!

I'm starting from the position in your latest post.

You need to place one more number in the puzzle before you can decide to put the "6" at r6c1. As it stands, you have {1, 2, 4, 8} in column 1, and {2, 3, 5, 8, 9} in row 6, so either a "6" or a "7" is possible in this square right now. Let's look for one other number.

Look first at the 3x3 box in the lower left corner (the intersection of rows 7, 8, & 9 with columns 1, 2, & 3). From the position of the "5"s in rows 8 and 9 it's clear that the only way to fit a "5" in this box is to place it in r9c1 or in r9c2. In other words, it has to go in column 1 or in column 2 -- it can't fit in column 3.

Now turn your attention to the first 3x3 box in the middle row (the intersection of rows 4, 5, & 6 with columns 1, 2, & 3). It's clear that "5" can only fit in this box if it goes in row 5 -- in r5c1 or in r5c2, to be precise. So we know that the "5" in this box has to fit in column 1 or in column 2 -- it can't fit in column 3.

The only way to fit a "5" in column 3, then, is if it goes in the first box (the intersection of rows 1, 2, & 3 with columns 1, 2, & 3). And since the first row already has a "5" at r5c5, the only place to put the "5" in that first box is at r2c3.

This process -- deducing that a particular number has to fit in a single column within a particular box -- is the "Column on Block" interaction others have written about.

Anyway, with five numbers placed in the first box, we see that the only four remaining as possibilities are {1, 2, 7, 9}. And since "1" and "2" already appear in the first column, we see that the pair {7, 9} must appear in r2c1 & r3c1, in some order. Similarly, the pair {1, 2} must appear in the cells r1c2 & r1c3, in some order.

Now the deduction that "6" goes in r6c1 is immediate, since the possibility of a "7" going there has been eliminated -- we know that the "7" in the first column has to fit in either r2c1 or in r3c1.

From here the puzzle falls into place pretty rapidly ... the next step is clearly a "1" in r6c4, and it's pretty much downhill from there.

I hope this helps with the "Column on Block" interaction concept. I'll try to write something on your other recent post soon. dcb

[someone_somewhere]

Hi,
David has pointed out correct, how to move one.
The buttom line is that you have to know how to apply 3 techniques:
- Row on 3x3 Block interaction,
- Column on 3x3 Block interaction and
- 3x3 Block on Row/Column interaction

The point you was stucked is a good exercise for learning them.
Here the short description for a possible to get home:
1 not in r1c7, it is in r2c7 or r2c8 (Row on 3x3 Block interaction)
1 not in r1c9, it is in r2c7 or r2c8 (Row on 3x3 Block interaction)
8 not in r7c8, it is in r7c9 or r8c9 (Column on 3x3 Block interaction)
7 not in r5c1, it is in r2c1 or r3c1 of the 3x3 (3x3 Block on Row/Column interaction)
7 not in r6c1, it is in r2c1 or r3c1 of the 3x3 (3x3 Block on Row/Column interaction)
3 not in r8c4, it is in r1c4 or r3c4 of the 3x3 (3x3 Block on Row/Column interaction)
6 in r6c1 - Sole Candidate

P.S. I can't beat the literar talent of David.

see u,

[Going Mad]

THANKS!!!!

Just finished it!!