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Can anyone help me solve this Sudoku?

 
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Elizabeth Daniel

Joined: 27 Dec 2005
Posts: 2
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PostPosted: Tue Dec 27, 2005 6:27 am    Post subject: Can anyone help me solve this Sudoku? Reply with quote
I received this Sudoku url from a friend. He says he's solved it up to here, but he's stuck:

http://www.freesudokuhost.com/showsudokuhosting.php?id=20051224213001997

I'm unable to move ahead either. I asked my friends, but no one is able to help.

I'm fairly good with Sudokus, and so is my friend who sent this to me. All I need is just the next step. I can (hopefully) solve it from there.

Thanks,

Elizabeth Daniel.
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rkral

Joined: 21 Oct 2005
Posts: 233
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PostPosted: Tue Dec 27, 2005 12:23 pm    Post subject: Re: Can anyone help me solve this Sudoku? Reply with quote
Elizabeth Daniel wrote:
All I need is just the next step. I can (hopefully) solve it from there.

Assuming your candidate list is similar to the below, a next step might be r3c1=6. r3c1<>3 because of a "turbotfish" in 3s at r3c1, r3c4, r1c6, r4c6, and r4c1. If r4c1<>3 then r3c4=3 ... and if r3c4<>3 then r4c1=3.
Code:

 *-----------------------------------------------------------*
 | 2346  3489  89    | 5     24   +38    | 69    7     1     |
 | 24    7     1     | 24    6     9     | 8     5     3     |
 |*36    389   5     |-38    7     1     | 4     2     69    |
 |-------------------+-------------------+-------------------|
 |+35    1     69    | 7     8    -36    | 29    4     259   |
 | 789   89    2     | 1     5     4     | 3     6     79    |
 | 345   34    67    | 36    9     2     | 1     8     57    |
 |-------------------+-------------------+-------------------|
 | 18    6     4     | 9     23    5     | 7     13    28    |
 | 78    2     3     | 468   1     678   | 5     9     468   |
 | 1789  5     789   | 2468  234   678   | 26    13    2468  |
 *-----------------------------------------------------------*
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tarek

Joined: 31 Dec 2005
Posts: 153
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Location: London, UK

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PostPosted: Thu Jan 05, 2006 2:44 pm    Post subject: Reply with quote
My human solver solves it like this (I've deleted all Naked single eliminations):
Code:

Starting Grid:

 . . . | 5 . . | . 7 1 
 . 7 1 | . 6 9 | 8 5 3 
 . . 5 | . 7 1 | 4 2 . 
-------+-------+------
 . 1 . | 7 8 . | . 4 . 
 . . 2 | 1 5 4 | 3 6 . 
 . . . | . 9 2 | 1 8 . 
-------+-------+------
 . 6 4 | 9 . 5 | 7 . . 
 . 2 3 | . 1 . | 5 9 . 
 . 5 . | . . . | . . . 

Cell 5 Has only 24 as valid Candidates (Hidden Double)
Eliminating 3 From Cell 76 (Box Line interaction)
Eliminating 3 From Cell 78 (Box Line interaction)
Cell 28 Has only 35 as valid Candidates (Hidden Triple)
Cell 46 Has only 345 as valid Candidates (Hidden Triple)
Eliminating 6 From Cell 3 (Box Line interaction)
Cell 1 Has only 2346 as valid Candidates (Naked Quad)
Cell 19 Has only 36 as valid Candidates (Naked Quad)
Whatever possibility in Cell 19, Cell 13 will always be 2 (Forcing Chains)
Whatever possibility in Cell 19, Cell 28 will always be 5 (Forcing Chains)
Whatever possibility in Cell 19, Cell 33 will always be 3 (Forcing Chains)
Whatever possibility in Cell 19, Cell 48 will always be 7 (Forcing Chains)
Whatever possibility in Cell 19, Cell 49 will always be 6 (Forcing Chains)
Whatever possibility in Cell 19, Cell 77 will always be 3 (Forcing Chains)


Now the last bit of forcing chains may fall to other techniques like colouring which is not in my solver. If you solve that by hand then good for you !!!

What an interesting puzzle !!!
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rkral

Joined: 21 Oct 2005
Posts: 233
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PostPosted: Thu Jan 05, 2006 3:18 pm    Post subject: Reply with quote
tarek wrote:
My human solver solves it like this ...

Eliminating 3 From Cell 76 (Box Line interaction)
.........
Cell 19 Has only 36 as valid Candidates (Naked Quad)

Making a human figure out that Cell 76 is row 9 col 4 ... and Cell 19 is row 3 col 1 is, errrr ... inhumane IMO. Laughing
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tarek

Joined: 31 Dec 2005
Posts: 153
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Location: London, UK

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PostPosted: Thu Jan 05, 2006 4:31 pm    Post subject: Reply with quote
rkral wrote:
Making a human figure out that Cell 76 is row 9 col 4 ... and Cell 19 is row 3 col 1 is, errrr ... inhumane


very funny , but it makes sense absolutely Very Happy
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