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I thought I was getting good, then ...

 
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Wed Jun 25, 2008 11:00 pm    Post subject: I thought I was getting good, then ... Reply with quote

This one trips me up:
Code:
Puzzle: M6498989sh(21)
+-------+-------+-------+
| . . 6 | . . 1 | 8 . . |
| 8 . . | . 7 . | . . 6 |
| . . . | . 3 6 | . . . |
+-------+-------+-------+
| . 7 . | 6 . 3 | . 5 . |
| 3 . 5 | . . . | 6 . 7 |
| . 8 9 | 4 . 7 | 3 2 . |
+-------+-------+-------+
| . . . | . 4 5 | . . . |
| 2 . . | . 1 . | . . 9 |
| . . 4 | . . 2 | 5 . . |
+-------+-------+-------+
Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Jun 26, 2008 5:15 am    Post subject: Reply with quote

The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid. After that I'm thinking Medusa is all that's left in my arsenal.

Last edited by Marty R. on Thu Jun 26, 2008 3:46 pm; edited 1 time in total
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Jun 26, 2008 6:34 am    Post subject: Reply with quote

Code:
.---------------------.---------------------.---------------------.
| 457    34     6     | 2      9      1     | 8      347    345   |
| 8      1239   123   | 5      7      4     | 12     139    6     |
| 14579  1249   127   | 8      3      6     | 127    1479   245   |
:---------------------+---------------------+---------------------:
| 14     7      12    | 6      28     3     | 9      5      48    |
| 3      24     5     | 1      28     9     | 6      48     7     |
| 6      8      9     | 4      5      7     | 3      2      1     |
:---------------------+---------------------+---------------------:
| 179    6      8     | 379    4      5     | 127    137    23    |
| 2      5      37    | 37     1      8     | 4      6      9     |
| 179    139    4     | 379    6      2     | 5      1378   38    |
'---------------------'---------------------'---------------------'


one step solution

xy-chain(3=8)r9c9-(8=4)r4c9-(4=1)r4c1-(1=2)r4c3-(2=4)r5c2-(4=3)r2c2; r9c2 and r1c9 <> 3
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Johan



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Thu Jun 26, 2008 10:54 am    Post subject: Reply with quote

Quote:
one step solution


Nice catch Norm !

These xy-chains maybe underestimated, but it solves this grid in one fell swoop. Nevertheless i like these chains, they can be a powerful tool to break the
puzzle wide open.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Thu Jun 26, 2008 12:03 pm    Post subject: Reply with quote

Marty R. wrote:
The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid.


Marty, I looked at the two potential <12>URs last night and again this morning after seeing you comments, but I still fail to see an elimination. (and yes, I had my coffee this morning.)

What is invalid? Question

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Jun 26, 2008 3:44 pm    Post subject: Reply with quote

tlanglet wrote:
Marty R. wrote:
The potential 12 rectangle solves a cell because the other two possibilities to avoid the DP are invalid.


Marty, I looked at the two potential <12>URs last night and again this morning after seeing you comments, but I still fail to see an elimination. (and yes, I had my coffee this morning.)

What is invalid? Question

Ted


Code:
.---------------------.---------------------.---------------------.
| 457    34     6     | 2      9      1     | 8      347    345   |
| 8      1239   123   | 5      7      4     | 12     139    6     |
| 14579  1249   127   | 8      3      6     | 127    1479   245   |
:---------------------+---------------------+---------------------:
| 14     7      12    | 6      28     3     | 9      5      48    |
| 3      24     5     | 1      28     9     | 6      48     7     |
| 6      8      9     | 4      5      7     | 3      2      1     |
:---------------------+---------------------+---------------------:
| 179    6      8     | 379    4      5     | 127    137    23    |
| 2      5      37    | 37     1      8     | 4      6      9     |
| 179    139    4     | 379    6      2     | 5      1378   38    |
'---------------------'---------------------'---------------------'

Ted, who knows, maybe I did something wrong, but to avoid the deadly pattern r2c3 must be = 3 or r3c3 must be = 7 or r3c7 must be = 7. The first and third possibilities led to invalid solutions, so I solved r3c3 = 7. As I type this I haven't yet finished the puzzle.

Quote:
These xy-chains maybe underestimated, but it solves this grid in one fell swoop. Nevertheless i like these chains, they can be a powerful tool to break the puzzle wide open.


They certainly can. I don't use them that often, but much of the time there's an XY-Chain when Medusa looks like a good possibility.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Thu Jun 26, 2008 9:06 pm    Post subject: Reply with quote

Code:
+-------------------+-------------------+-------------------+
| 457   34f   6     | 2     9     1     | 8     347  -345   |
| 8     1239  123   | 5     7     4     | 12    139   6     |
| 14579 1249  127   | 8     3     6     | 127   1479  245   |
+-------------------+-------------------+-------------------+
| 14    7     12    | 6     28    3     | 9     5     48b   |
| 3     24e   5     | 1     28d   9     | 6     48c   7     |
| 6     8     9     | 4     5     7     | 3     2     1     |
+-------------------+-------------------+-------------------+
| 179   6     8     | 379   4     5     | 127   137   23    |
| 2     5     37    | 37    1     8     | 4     6     9     |
| 179  1-39   4     | 379   6     2     | 5     1378  38a   |
+-------------------+-------------------+-------------------+
There is a similar chain (abcdef) that starts to make sense for me:

In R5 e and f sort of collapse into <48> and the chain looks like 38 48 48 48 34 which is an XY-wing with coloring on the pivot.

Keith
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