help: advanced sudoku i need advice on...

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help: advanced sudoku i need advice on...

Postby bollib » Wed Nov 08, 2006 1:15 am

any hints on that one:?:

http://members.chello.at/oliver.bach/sudo_hard.jpg

(i was able to enter the black-colored numbers but there are many
blank spaces left:( - as you can see)

thanks
Last edited by bollib on Tue Nov 07, 2006 9:29 pm, edited 1 time in total.
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Re: help: advanced sudoku i need advice on...

Postby re'born » Wed Nov 08, 2006 1:25 am

bollib wrote:any hints on that one:?:

http://members.chello.at/oliver.bach/sudo_hard.jpg

thanks


The puzzle is at the following position.
Code: Select all
 

 *-----------*
 |26.|...|..3|
 |.54|6.2|.9.|
 |...|...|6.2|
 |---+---+---|
 |94.|.6.|...|
 |.2.|5.4|916|
 |6..|.9.|..4|
 |---+---+---|
 |7.8|.56|..1|
 |512|743|869|
 |4.6|...|.75|
 *-----------*

 
 *--------------------------------------------------------------------*
 | 2      6      179    | 1489   178    15789  | 1457   458    3      |
 | 138    5      4      | 6      1378   2      | 17     9      78     |
 | 138    3789   1379   | 13489  1378   15789  | 6      458    2      |
 |----------------------+----------------------+----------------------|
 | 9      4      1357   | 1238   6      178    | 2357   2358   78     |
 | 38     2      37     | 5      378    4      | 9      1      6      |
 | 6      378    1357   | 1238   9      178    | 2357   2358   4      |
 |----------------------+----------------------+----------------------|
 | 7      39     8      | 29     5      6      | 234    234    1      |
 | 5      1      2      | 7      4      3      | 8      6      9      |
 | 4      39     6      | 1289   128    189    | 23     7      5      |
 *--------------------------------------------------------------------*


My first suggestion is to look at column 5 to see if there is any number that can only go in one cell. There are more interesting exclusions later, but lets see if this gets you on the right track.
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Postby bollib » Wed Nov 08, 2006 7:13 pm

thanks for your quick response!
after a little more thinking the grid looks like this

Code: Select all
-------------
|26.|...|..3|
|.54|6.2|.9.|
|...|...|6.2|
-------------
|94.|.6.|...|
|.2.|5.4|916|
|6..|.9.|..4|
-------------
|738|956|..1|
|512|743|869|
|496|.2.|375|
-------------


now i'm stuck again:(
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Postby Carcul » Wed Nov 08, 2006 8:03 pm

Hi Bollib.

Look at box 4: candidate "1" can only go in cells belonging to column 3 (or, in other words, what do you think about cells r5c1/r5c3/r6c2?). Next apply the same reasoning to the same candidate in box 2. That should help you.

Carcul
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Postby bollib » Thu Nov 09, 2006 3:30 am

hi carcul!

i'm sorry but your tip doesnt help me alot because digit "1" appears as
a potential candidate in many boxes and there are not enough occurrences where i can eliminate that one.

so could you please give me a bit more detailed description on solving.

thanks
bollib
 
Posts: 4
Joined: 07 November 2006

Postby RW » Thu Nov 09, 2006 8:37 am

Hi Bollib

The path showed by carcul does lead to the solution, but it's not very simple. I think I have one that could be easier, focus on columns 4, 5 and 6:
Code: Select all
...
6.2
...
---
.6.
5.4
.9.
---
956
743
.2.


Look at digits 5 and 9 in column 4 and 5. What is the implication caused by these numbers in box 2? Now look at the 7 in column 4. Combined with what you learned from the 5s and 9s, what are the possible cells for 7 in box 2? What is the effect of this when you look at the rest of that column, IOW what would happen if there was a 7 in r5c5?

RW
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Postby nosharpe » Thu Nov 09, 2006 1:48 pm

The clue to solving this puzzle is to eliminate.
To understand the process of elimination, go to www.scanraid.com/sudoku.htm where you will find excellent tutorials on this subject (links are located on the right side of the site)

PS. From the info provided thus far, this would lead you to place a 7 at R5C3. Easily solved from there
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Postby bollib » Thu Nov 09, 2006 6:59 pm

@all:
thanks for the kind help. it's greatly appreciated

@nosharpe:
the link you provided is really excellent. i'll soon be a real sudoku expert:D
bollib
 
Posts: 4
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