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		| Earl 
 
 
 Joined: 30 May 2007
 Posts: 677
 Location: Victoria, KS
 
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				|  Posted: Sat Apr 10, 2010 3:25 am    Post subject: April 10 VH |   |  
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				| I could not find a single bullet.  Had to use a double-barreled shotgun., 
 Solution:  X-wing (1), xy-wing (238)
 
 Early Earl
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		| Marty R. 
 
 
 Joined: 12 Feb 2006
 Posts: 5770
 Location: Rochester, NY, USA
 
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				|  Posted: Sat Apr 10, 2010 3:51 am    Post subject: |   |  
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				| W-Wing on 26 did the job. |  | 
	
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		| peterj 
 
 
 Joined: 26 Mar 2010
 Posts: 974
 Location: London, UK
 
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				|  Posted: Sat Apr 10, 2010 9:50 am    Post subject: |   |  
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				| I went looking for xy-chains but stumbled on a forcing chain (don't normally go there..) that does it in one - not pretty! 
 
  	  | Quote: |  	  | Consider r1c5, (2)r1c5-(6)r1c8-(3)r1c2-(7)r1c1-(3)r8c1-(9)r8c6-(4)r9c6
 or
 (4)r1c5-(6)r9c5-(9)r9c1-(4)r9c6
 r9c6=4
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 I am still learning W-wings but I could not see the single (or odd number) of strong links connecting the pairs on 6?
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		| tlanglet 
 
 
 Joined: 17 Oct 2007
 Posts: 2468
 Location: Northern California Foothills
 
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				|  Posted: Sat Apr 10, 2010 11:21 am    Post subject: |   |  
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				| A single step xyz-wing 268 in r3c8 with a loooong tail. 
  	  | Code: |  	  | *-----------------------------------------------------------*
 | 37    36    8     | 1246  24    5     | 9     26    127   |
 | 2     5     67    | 169   3     189   | 18    4     178   |
 | 1     9     4     | 26    28    7     | 3     268   5     |
 |-------------------+-------------------+-------------------|
 | 69    26    1269  | 8     7     14    | 5     23    1234  |
 | 5     4     12    | 3     9     6     | 18    7     128   |
 | 8     7     3     | 14    5     2     | 6     9     14    |
 |-------------------+-------------------+-------------------|
 | 4     236   26    | 5     268   38    | 7     1     9     |
 | 37    8     279   | 29    1     39    | 4     5     6     |
 | 69    1     5     | 7     46    49    | 2     38    38    |
 *-----------------------------------------------------------*
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 (2)r3c8; r1c9<>2
 (6)r3c8 - (6=2)r1c8; r1c9<>2
 (8)r3c8 - r3c5 = r2c6 - (8=3)r7c6 - (3=9)r8c6 - r9c6 = r9c1 - (9=6)r4c1 - (6=2)r4c2 - r4c89 = r5c9; r1c9<>2
 Thus r1c9<>2 to complete the puzzle.
 
 Ted
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		| Wendy W 
 
 
 Joined: 04 Feb 2008
 Posts: 144
 
 
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				|  Posted: Sat Apr 10, 2010 11:03 pm    Post subject: |   |  
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				| What Early Earl said. I went looking for XY-wings and XYZ-wings first and couldn't find a single one that did anything -- that's rare! |  | 
	
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		| Marty R. 
 
 
 Joined: 12 Feb 2006
 Posts: 5770
 Location: Rochester, NY, USA
 
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				|  Posted: Sat Apr 10, 2010 11:07 pm    Post subject: |   |  
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				|  	  | Quote: |  	  | I am still learning W-wings but I could not see the single (or odd number) of strong links connecting the pairs on 6? | 
 Peter, the 26 cells in boxes 47 are connected by the 6s in c1.
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		| cgordon 
 
 
 Joined: 04 May 2007
 Posts: 769
 Location: ontario, canada
 
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				|  Posted: Sat Apr 10, 2010 11:44 pm    Post subject: |   |  
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				| I didn't bother with too many of the basics but rather brilliantly used  4 ERs - and then an xyz for the kill. |  | 
	
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		| storm_norm 
 
 
 Joined: 18 Oct 2007
 Posts: 1741
 
 
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				|  Posted: Sun Apr 11, 2010 12:54 am    Post subject: |   |  
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				|  	  | peterj wrote: |  	  | I went looking for xy-chains but stumbled on a forcing chain (don't normally go there..) that does it in one - not pretty! 
 
  	  | Quote: |  	  | Consider r1c5, (2)r1c5-(6)r1c8-(3)r1c2-(7)r1c1-(3)r8c1-(9)r8c6-(4)r9c6
 or
 (4)r1c5-(6)r9c5-(9)r9c1-(4)r9c6
 r9c6=4
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 I am still learning W-wings but I could not see the single (or odd number) of strong links connecting the pairs on 6?
 | 
 
 you did find a xy-chain.  its a very long one.
 but here it is.
 
 
  	  | Code: |  	  | +------------------+------------------+----------------+ | (37)  (36)  8    | 1246  (24)  5    | 9   (26)  127  |
 | 2     5     67   | 169   3     189  | 18  4     178  |
 | 1     9     4    | 26    28    7    | 3   268   5    |
 +------------------+------------------+----------------+
 | 69    26    1269 | 8     7     14   | 5   23    1234 |
 | 5     4     12   | 3     9     6    | 18  7     128  |
 | 8     7     3    | 14    5     2    | 6   9     14   |
 +------------------+------------------+----------------+
 | 4     236   26   | 5     268   38   | 7   1     9    |
 | (37)  8     27-9 | 29    1     (39) | 4   5     6    |
 | (69)  1     5    | 7     (46)  4-9  | 2   38    38   |
 +------------------+------------------+----------------+
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 (9=6)r9c1 - (6=4)r9c5 - (4=2)r1c5 - (2=6)r1c8 - (6=3)r1c2 - (3=7)r1c1 - (7=3)r8c1 - (3=9)r8c6;
 so neither the 9 at r9c1 nor the 9 at r8c6 can both be false.
 this eliminates the 9 at r9c6 and r8c3.
 
 
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		| peterj 
 
 
 Joined: 26 Mar 2010
 Posts: 974
 Location: London, UK
 
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				|  Posted: Sun Apr 11, 2010 8:19 am    Post subject: |   |  
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				| Marty, Doh! looking at wrong pair of 26...   
 Norm, thanks. I guess when  you find a 'forcing chain' you can always find a better way of expressing it - xy-chain, AIC. The truth is I just plugged two numbers in the cell and saw it forced a result. Suppose this is the heart of the 'are forcing chains trial and error' rather than 'pattern finding' question. To me it's the process that matters and not what you call it at the end of the day! This time I was close to the trial and error side!
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		| storm_norm 
 
 
 Joined: 18 Oct 2007
 Posts: 1741
 
 
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				|  Posted: Mon Apr 12, 2010 5:30 am    Post subject: |   |  
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				|  	  | Quote: |  	  | The truth is I just plugged two numbers in the cell and saw it forced a result. | 
 
 stop and think about that.
 
 you did it because you saw that at least one of the two candidates in r1c5 had to be true.
 we call this a strong inference.
 did you know that the candidates in that cell are weakly inferenced as well?
 weak inference - at the most, one candidate can be true.
 
 in fact, it doesn't matter how many candidates remain in any cell.  those candidates would be both strongly inferenced and weakly inferenced.
 
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		| Ema Nymton 
 
 
 Joined: 17 Apr 2009
 Posts: 89
 
 
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				|  Posted: Mon Apr 12, 2010 9:43 am    Post subject: |   |  
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 No solution ...
 
 
 
  	  | Code: |  	  | +-------------+--------------+-------------+
 | 37 36  8    | 1246 24  5   | 9  26  127  |
 | 2  5   67   | 169  3   189 | 18 4   178  |
 | 1  9   4    | 26   28  7   | 3  268 5    |
 +-------------+--------------+-------------+
 | 69 26  1269 | 8    7   14  | 5  23  1234 |
 | 5  4   12   | 3    9   6   | 18 7   128  |
 | 8  7   3    | 14   5   2   | 6  9   14   |
 +-------------+--------------+-------------+
 | 4  236 26   | 5    268 38  | 7  1   9    |
 | 37 8   279  | 29   1   39  | 4  5   6    |
 | 69 1   5    | 7    46  49  | 2  38* 38   |
 +-------------+--------------+-------------+
 
 | 
 
 
 Draw/Play gives a hint of '8' at r9c8.
 Is it possible to show the line of reasoning for the hint?
 
 (To help master the challenge one must first understand the challenger.  One of the reasons I visit this discussion board is to help learn the reasoning of the puzzler.)
 
 Ema Nymton
 ~@:o|
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		| nataraj 
 
 
 Joined: 03 Aug 2007
 Posts: 1048
 Location: near Vienna, Austria
 
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				|  Posted: Mon Apr 12, 2010 10:37 am    Post subject: |   |  
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				|  	  | Ema Nymton wrote: |  	  | . 
 (To help master the challenge one must first understand the challenger.  One of the reasons I visit this discussion board is to help learn the reasoning of the puzzler.)
 
 Ema Nymton
 ~@
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 My advice: do not try to understand the program.
 There is no challenger.
 There is nobody even remotely human there.
 It is just a piece of software.
 
 The "hint" is not a hint.
 The program does not give hints. It does not tell you about the next step. It says which cell it solved next.
 
 Imagine you come to a crossroad. Three roads, no signpost. Your problem is, which of the roads to take.
 The "hint" says: "You may arrive in Oz".
 
 How to help your solving abilities then?
 Read the solutions in this forum. Ask questions. If you like computer help, get a decent piece of software that actually explains what it is doing, or at least describes the next step.
 
 In this case, the next step is x-wing (1) rows 1 and 4.
 With 1 gone from r5c9, there is now an xy-wing that eliminates 3 from r9c8.
 Which leaves 8 in r9c8.
 This is Earl's solution (first post in this thread). You have to highlight the text to make the hints (the REAL hints
  ) visible ... |  | 
	
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		| Ema Nymton 
 
 
 Joined: 17 Apr 2009
 Posts: 89
 
 
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				|  Posted: Mon Apr 12, 2010 12:35 pm    Post subject: |   |  
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				| . 
 Thank you.  The puzzles are becoming more challenging.   Your helpful explanation did help me to sort out a reasonable workable solution.
 
 _____
 My advice: do not try to understand the program.
 There is no challenger.
 There is nobody even remotely human there.
 It is just a piece of software.
 
 ... snip ...
 _____
 
 Hopefully even if  there is nothing more to this puzzle than 'just a piece of software,' the underlying concept is that solutions are humanly understandable and discernible.
 
 Ema Nymton
 ~@:o)
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		| nataraj 
 
 
 Joined: 03 Aug 2007
 Posts: 1048
 Location: near Vienna, Austria
 
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				|  Posted: Mon Apr 12, 2010 1:07 pm    Post subject: |   |  
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				| Ema, 
 you might want to check out Danny's puzzles here in this forum.
 
 Not only are they good puzzles, but on top of that you have the opportunity to discuss with the creator of the puzzles.
 
 To discuss "humanly understandable solutions" ... well that's what this forum is about
   
 Nataraj
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		| ttt 
 
 
 Joined: 06 Dec 2008
 Posts: 42
 Location: vietnam
 
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				|  Posted: Mon Apr 12, 2010 4:15 pm    Post subject: |   |  
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				|  	  | Ema Nymton wrote: |  	  | My advice: do not try to understand the program. There is no challenger.
 There is nobody even remotely human there.
 It is just a piece of software.
 | 
 
  	  | Code: |  	  | *-----------------------------------------------------------* | 37    36    8     | 1246  24    5     | 9     26    127   |
 | 2     5     67    | 169   3     189   | 18    4     178   |
 | 1     9     4     | 26    28    7     | 3     268   5     |
 |-------------------+-------------------+-------------------|
 | 69    26    1269  | 8     7     14    | 5     23    1234  |
 | 5     4     12    | 3     9     6     | 18    7     128   |
 | 8     7     3     | 14    5     2     | 6     9     14    |
 |-------------------+-------------------+-------------------|
 | 4     236   26    | 5     268   38    | 7     1     9     |
 | 37    8     279   | 29    1     39    | 4     5     6     |
 | 69    1     5     | 7     46    49    | 2     38    38    |
 *-----------------------------------------------------------*
 | 
 Don’t know some softwares can find this: Look at AUR(18)r25c79 => (2)r5c9=(7)r2c9
 AUR(18)r25c79: (2)r5c9=(7)r2c9-(7=6)r2c3-(6=2)r7c3 => r5c3<>2 then singles to the end
 
 ttt
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		| Luke451 
 
 
 Joined: 20 Apr 2008
 Posts: 310
 Location: Southern Northern California
 
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				|  Posted: Mon Apr 12, 2010 7:50 pm    Post subject: |   |  
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				|  	  | tlanglet wrote: |  	  | A single step xyz-wing 268 in r3c8 with a loooong tail. 
  	  | Code: |  	  | *-----------------------------------------------------------*
 | 37    36    8     | 1246  24    5     | 9     26    127   |
 | 2     5     67    | 169   3     189   | 18    4     178   |
 | 1     9     4     | 26    28    7     | 3     268   5     |
 |-------------------+-------------------+-------------------|
 | 69    26    1269  | 8     7     14    | 5     23    1234  |
 | 5     4     12    | 3     9     6     | 18    7     128   |
 | 8     7     3     | 14    5     2     | 6     9     14    |
 |-------------------+-------------------+-------------------|
 | 4     236   26    | 5     268   38    | 7     1     9     |
 | 37    8     279   | 29    1     39    | 4     5     6     |
 | 69    1     5     | 7     46    49    | 2     38    38    |
 *-----------------------------------------------------------*
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 (2)r3c8; r1c9<>2
 (6)r3c8 - (6=2)r1c8; r1c9<>2
 (8)r3c8 - r3c5 = r2c6 - (8=3)r7c6 - (3=9)r8c6 - r9c6 = r9c1 - (9=6)r4c1 - (6=2)r4c2 - r4c89 = r5c9; r1c9<>2
 Thus r1c9<>2 to complete the puzzle.
 
 Ted
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 ALS version just for interest (italics=your chain):
 
 (26=8)als:r13c8- r3c5 = r2c6 - (8=3)r7c6 - (3=9)r8c6 - r9c6 = r9c1 - (9=6)r4c1 - (6=2)r4c2 - r4c89 = r5c9; r1c9<>2
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