Can't go on

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Can't go on

Postby dgmuller » Sat Feb 25, 2006 8:36 pm

3 6 49 89 7 1 2 48 5
8 7 49 5 2 6 1 3 49
1 2 5 3 4 89 78 6 79

4 9 7 6 3 2 5 1 8
5 1 6 479 8 479 47 2 3
2 8 3 1 5 47 6 9 47

7 4 8 2 1 3 9 5 6
9 3 2 48 6 5 48 7 1
6 5 1 478 9 478 3 48 2
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Postby vidarino » Sat Feb 25, 2006 9:49 pm

There are a couple of methods of progress from here by attacking the 8s.

There's a "Hinge" (a.k.a. Empty Rectangle - see separate thread in "Advanced Solving Techniques" for an in-depth explanation), which might be the easiest to spot. Also, you can use a Turbot Fish or simple coloring.

As an example of the latter, here's the result of coloring the 8s:
Code: Select all
 . . . | a . . | . A .
 . . . | . . . | . . .
 . . . | . . A | a . .
-------+-------+------
 . . . | . . . | . . .
 . . . | . . . | . . .
 . . . | . . . | . . .
-------+-------+------
 . . . | . . . | . . .
 . . . | a . . | A . .
 . . . | x . a | . a .


(Since there are two 'a's in box 8, it means that picking those will lead to a conflicting grid, and therefore A is the correct color.)

Should get you on your way.:)

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Postby sweetbix » Sat Feb 25, 2006 10:58 pm

I've been looking at the threads on loops. Can someone tell me if this is the right way to notate the chain for this puzzle as aloop.

r1c4=8 => r1c8=4 => r9c8=8 => r8c7=4 => r8c4=8 = contradiction => r1c4<>8

[r1c4]–8–[r1c8]-4-[r9c8]-8-[r8c7]-4-[r8c4]-8-[r1c4]-4?

Thanks.
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Postby vidarino » Sat Feb 25, 2006 11:07 pm

sweetbix wrote:I've been looking at the threads on loops. Can someone tell me if this is the right way to notate the chain for this puzzle as aloop.

r1c4=8 => r1c8=4 => r9c8=8 => r8c7=4 => r8c4=8 = contradiction => r1c4<>8

[r1c4]–8–[r1c8]-4-[r9c8]-8-[r8c7]-4-[r8c4]-8-[r1c4]-4?


I'm no notation expert, but those look fine to me. In the last one, however, you don't need to include the last "-4", since the last "-8-[R1C4]" basically says "excludes 8 from R1C4" (which obviously isn't true, since that was the starting point).
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Postby tarek » Sun Feb 26, 2006 7:12 pm

You can also use another advanced technique, the finned fish....

here u have a finned x-wing
Code: Select all
*-----------------------------------------------*
| 3    6    49  |*89   7    1   | 2   *48   5   |
| 8    7    49  | 5    2    6   | 1    3    49  |
| 1    2    5   | 3    4    89  | 78   6    79  |
|---------------+---------------+---------------|
| 4    9    7   | 6    3    2   | 5    1    8   |
| 5    1    6   | 479  8    479 | 47   2    3   |
| 2    8    3   | 1    5    47  | 6    9    47  |
|---------------+---------------+---------------|
| 7    4    8   | 2    1    3   | 9    5    6   |
| 9    3    2   |#48   6    5   | 48   7    1   |
| 6    5    1   |*478  9   -478 | 3   *48   2   |
*-----------------------------------------------*
Eliminating 8 From r9c6 (Finned XWing in Columns 48)


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Postby MCC » Mon Feb 27, 2006 4:51 pm

Tarak can you tell me why r8c4 was chosen as the Fin and not r9c6?

As I can see, either could be chosen as the Fin, so am a bit confused as to why one was chosen over the other.

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Postby tarek » Mon Feb 27, 2006 9:07 pm

MCC wrote:Tarak can you tell me why r8c4 was chosen as the Fin and not r9c6?

As I can see, either could be chosen as the Fin, so am a bit confused as to why one was chosen over the other.

MCC


You are quite right , r8c4 is the fin when the xwing is columns while r9c6 is the fin when the x-wing is in rows

No real preference

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Postby MCC » Tue Feb 28, 2006 5:37 pm

Thanks Tarak, I can see it now, I was a bit tired yesterday and didn't see beyond the initial elimination.

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