dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

august 28

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku puzzles
View previous topic :: View next topic  
Author Message
hollydoll
Guest





PostPosted: Tue Aug 30, 2005 2:53 pm    Post subject: august 28 Reply with quote

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
Back to top
Guest






PostPosted: Tue Aug 30, 2005 5:20 pm    Post subject: Reply with quote

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?
Back to top
chobans



Joined: 21 Aug 2005
Posts: 39

PostPosted: Tue Aug 30, 2005 6:20 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Hollydoll
Guest





PostPosted: Tue Aug 30, 2005 7:19 pm    Post subject: Aug 28 Reply with quote

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
Back to top
someone_somewhere



Joined: 07 Aug 2005
Posts: 275
Location: Munich

PostPosted: Tue Aug 30, 2005 8:48 pm    Post subject: Reply with quote

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,
Back to top
View user's profile Send private message
David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Tue Aug 30, 2005 9:03 pm    Post subject: Re: Aug 28 Reply with quote

Hollydoll wrote:
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


Start by looking at the third box (intersection of r1-3 with c7-9). Because of the "8"s in row 1 and in column 7, you can see that the "8" in this box has to go in column 8 -- either in r2c8, or in r3c8. This implies that the "8" in box 9 must go in column 9 -- specifically, in either r7c9 or r8c9.

That leaves only one place to put an "8" in row 9 -- it has to go in r9c3. It can't fit in the first two columns because of the "8"s in r1c1 and r6c2; it can't fit in column 5 because of the "8" in r4c5; and it can't fit in column 7 or column 8 because we know the "8" in the ninth box has to be in either row 7 or row 8 -- not in row 9.

I'm sort of in a hurry right now ... what I do see about the "4" in box 3 is that it has to go in column 8. There are only 2 possible spots for a "4" in the ninth box (r8c7 or r8c9) and there are only two spots in the 6th box (r4c9 and r6c7) where the "4" can go -- so the only way a "4" can fit in the 8th column is if it's in one of the first three rows. This gives us two numbers {4,8} that have to fit in the three cells r1c8, r2c8, r3c8 -- I don't see what the third one has to be, right off -- maybe you can figure that out.

Good luck! dcb
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Bruno
Guest





PostPosted: Wed Aug 31, 2005 10:50 am    Post subject: Reply with quote

someone_somewhere wrote:

you can take a look at:
http://www.simes.clara.co.uk/programs/sudokutechniques.htm


Thanks for this useful techniques !

But, i can't understand the Swordfish one

Coul'd you help me please ?
Back to top
David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Wed Aug 31, 2005 1:03 pm    Post subject: Re: Swordfish Reply with quote

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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Bruno
Guest





PostPosted: Thu Sep 01, 2005 12:46 pm    Post subject: Reply with quote

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

I'll check your example later !
Back to top
Guest






PostPosted: Thu Sep 01, 2005 1:37 pm    Post subject: X-wing, Swordfish, Jellyfish and Squirmbag ... Reply with quote

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,
Back to top
someone_somewhere



Joined: 07 Aug 2005
Posts: 275
Location: Munich

PostPosted: Thu Sep 01, 2005 1:41 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Going Mad...
Guest





PostPosted: Sat Sep 03, 2005 3:21 pm    Post subject: Why the Number 6 in Box 4? Reply with quote

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?
Back to top
someone_somewhere



Joined: 07 Aug 2005
Posts: 275
Location: Munich

PostPosted: Sat Sep 03, 2005 6:13 pm    Post subject: Reply with quote

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,
Back to top
View user's profile Send private message
Going Mad
Guest





PostPosted: Sat Sep 03, 2005 7:07 pm    Post subject: Reply with quote

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!
Back to top
David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Sat Sep 03, 2005 10:57 pm    Post subject: Column on Block interaction is the clue Reply with quote

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 Smile
Back to top
View user's profile Send private message Send e-mail Visit poster's website
someone_somewhere



Joined: 07 Aug 2005
Posts: 275
Location: Munich

PostPosted: Sun Sep 04, 2005 6:03 am    Post subject: Reply with quote

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,
Back to top
View user's profile Send private message
Going Mad
Guest





PostPosted: Sun Sep 04, 2005 9:38 am    Post subject: Reply with quote

THANKS!!!!

Just finished it!!
Back to top
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku puzzles All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group