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Sep 21 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1110
Location: Dar es Salaam Tanzania
PostPosted: Mon Sep 20, 2010 9:54 pm    Post subject: Sep 21 VH Reply with quote
Remote Pairs 13 solve it by removing 3 in r8c7.
Also an XY-Wing 15 35 13 Pivoted in BOX 8 removing 1 in r8c4 does it as well.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Tue Sep 21, 2010 12:43 am    Post subject: Reply with quote
This was a good puzzle to look for various solutions. In addition to Clement's methods, there's a Finned X-Wing on 3 and a flightless M-Wing on 39.

Also--and I don't know if I did this properly--a Ted-style external analysis on the Type 6 UR on 36 yields r5c8<>3.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Wed Sep 22, 2010 4:54 am    Post subject: Reply with quote
Marty R. wrote:
Also--and I don't know if I did this properly--a Ted-style external analysis on the Type 6 UR on 36 yields r5c8<>3.


Marty, Glad that you are trying external analysis. You did not provide details so it is not possible to comment on the steps you took.

Here is the code after basics:
Code:
*--------------------------------------------------*
 | 2    4    7    |*368  9    38   | 5   *36   1    |
 | 3    6    9    | 15   7    15   | 8    4    2    |
 | 5    8    1    |*36   4    2    | 7   *369  39   |
 |----------------+----------------+----------------|
 | 6    9    4    | 7    8    13   | 13   2    5    |
 | 8    7    5    | 2    13   6    | 139  39   4    |
 | 1    3    2    | 4    5    9    | 6    7    8    |
 |----------------+----------------+----------------|
 | 9    1    6    | 35   2    357  | 4    8    37   |
 | 7    2    8    | 139  13   4    | 39   5    6    |
 | 4    5    3    | 89   6    78   | 2    1    79   |
 *--------------------------------------------------*


The type 6 UR (36)r13c48 is marked *.

As Danny reminded me recently, a type 6 UR has an x-wing overlay, which is this case is UR digit 6. Thus we immediately know that there are no external cells containing a digit 6 that share a house with the AUR cells. Therefore no further analysis for UR digit 6 is required.

For digit 3, I found the following;
1. AUR cells r13c4 share a column with r78c4
2. AUR cells r13c4 share a box with r1c6
3. AUR cells r13c8 share a column with r5c8
4. AUR cells r13c8 share a box with r3c9
5. AUR cells r1c48 share a row with r1c6
6. AUR cells r3c48 share a row with r3c9

Again Principle 2 states that every UR digit must be covered by "one" shared house, if any exist. Given the six statements above regarding external cells that share a house with the UR digits, we have many combinations to satisfy this requirement. For example, if we use statement 5 & 6, then all four of the UR cells see an external cell; r1c48 sees r1c6 and r3c48 sees r3c9. This results in two conditions: either r1c6=3 and/or r3c9=3 to prevent the deadly pattern. These two cells then act as pincers to delete 3 from r1c8 and r3c4.

Another combination of external cells to cover all the AUR cells is
statements 1 & 4; r13c4 sees r78c4, and r13c8 sees r3c9. If r78c4=3 then r13c4<>3, then r1c6=3 which makes r1c8<>3.

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Sep 22, 2010 5:08 am    Post subject: Reply with quote
Ted, I don't know exactly what I did, but I concluded that r5c8<>3, but I can't re-create it right now. I think I had the principles right, if not the mechanics.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Sep 22, 2010 5:36 pm    Post subject: Reply with quote
Ted, as you are obviously aware, the two analyses above yield the same result as playing the Type 6.

Using statements 5&6:

R1c6=3--->r5c5=3
R3c9=3--->r8c7=3

These pincers force r8c5<>3, solving the puzzle, my first experience at successfully using the external analysis.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
PostPosted: Thu Sep 23, 2010 2:42 am    Post subject: Reply with quote
Marty R. wrote:
Ted, as you are obviously aware, the two analyses above yield the same result as playing the Type 6.

Using statements 5&6:

R1c6=3--->r5c5=3
R3c9=3--->r8c7=3

These pincers force r8c5<>3, solving the puzzle, my first experience at successfully using the external analysis.


Congratulations Marty Exclamation Exclamation Very Happy

If you continue to use external analysis for general ADPs, I think you will find that it is more flexible and offers more opportunities for different deletions than those offered by internal analysis. I have found that I get essentially the same results as internal analysis for the Type 1-6 URs.

Ted
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