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Astraware Diabolical - sometimes hard, sometimes not

 
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK
PostPosted: Tue Nov 09, 2010 6:00 pm    Post subject: Astraware Diabolical - sometimes hard, sometimes not Reply with quote
Code:
 *-----------*
 |.7.|5..|...|
 |92.|1..|...|
 |4.3|...|..2|
 |---+---+---|
 |5..|..9|.74|
 |..8|347|9..|
 |79.|2..|..1|
 |---+---+---|
 |6..|...|3.8|
 |...|..1|.49|
 |...|..5|.6.|
 *-----------*
Astraware Diabolical 291010

The ones >20,000 difficulty are sometimes interesting.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Nov 10, 2010 12:57 am    Post subject: Reply with quote
The first time I tried this I ended with an invalidity and had to erase and start over. Maybe I've got a mistake the 2nd time around too, but I can't get far enough to find out. I quickly played a W-Wing, M-Wing and XYZ-Wing and then hit the brick wall. I'm not giving up just yet, but I thought I'd be able to see something there with all the bivalues, but I haven't.

Code:

+------------+--------------+------------+
| 8  7   16  | 5    2    34 | 14  9   36 |
| 9  2   56  | 1    78   34 | 457 58  36 |
| 4  15  3   | 6789 6789 68 | 17  158 2  |
+------------+--------------+------------+
| 5  3   2   | 68   1    9  | 68  7   4  |
| 1  6   8   | 3    4    7  | 9   2   5  |
| 7  9   4   | 2    5    68 | 68  3   1  |
+------------+--------------+------------+
| 6  145 579 | 479  79   2  | 3   15  8  |
| 23 8   57  | 67   367  1  | 25  4   9  |
| 23 14  19  | 489  389  5  | 12  6   7  |
+------------+--------------+------------+

Play this puzzle online at the Daily Sudoku site
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Wed Nov 10, 2010 2:20 am    Post subject: Reply with quote
Marty,

There is a 68 DP: R3C4<>68.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Nov 10, 2010 2:28 am    Post subject: Reply with quote
Keith, I can't get far with that DP.

However, before I saw your post I played Medusa and a wrap resulted in an invalidity, so maybe the grid's wrong. At any rate, I'll give it another try.

Regardless, I need to be more aware of the DPs that aren't as obvious as the ones in parallel lines.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Wed Nov 10, 2010 4:17 am    Post subject: Reply with quote
Marty,

Your grid is valid. The DP elimination does not solve it.

After the DP elimination, I think you need an XY-chain to solve it.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Nov 10, 2010 4:42 am    Post subject: Reply with quote
Grid is valid? I already erased it. I must've screwed up the Medusa then. Mad
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Wed Nov 10, 2010 6:03 am    Post subject: Reply with quote
Finally:

M-Wing, Keith's DP, Medusa wrap, XY-Chain, Type 6 UR and BUG+1.
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK
PostPosted: Wed Nov 10, 2010 7:16 am    Post subject: Reply with quote
My first run through I need a bunch of chains..
Code:
xyz-wing(18-5) r3c8 ; r3c7<>5
kite(5) r3, c7 ; r8c2<>5
w-wing-like(78) pseudocell ; (7=6)r8c4-(6=8)r4c4 - r6c6=r4c6 - 8=7)r2c5 ; r3c4<>7, r78c5<>7
xy-chain ; (7=8)r2c5 - (8=3)r9c5 - (3=2)r9c1 - (2=1)r9c7 - (1=7)r3c7 ; r2c7<>7, r3c5<>7
BUG+2 ; r7c2<>5

I had another go and looked for ALS, got it down to two steps!
Code:
xy-chain with ALS ; (8=6)r3c6 - ANT(6=789)r237c5 - (89=3)r9c5 - (3=2)r9c1 - (2=1)r9c7 - (1=5)r7c8 - (5=8)r2c8 ; r3c8<>8, r2c5<>8
finned x-wing(1) r3, r7 ; r9c2<>1
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Wed Nov 10, 2010 3:14 pm    Post subject: Reply with quote
Solver: <18+5> XYZ-Wing r3c7<>5, Kite r7c3<>1, Kite r8c2<>5, and 9-cell XY-Chain r2c5,r3c8<>8.

Playing with it: Kite r7c3<>1, finned 9-cell XY-Chain w/fin r8c4=8.




Peter, your ALS as ANQ():

xy-chain with ALS ; (8=6)r3c6 - ANQ(6=789+3)r3279c5 - (3=2)r9c1 - (2=1)r9c7 - (1=5)r7c8 - (5=8)r2c8 ; r2c5,r3c8<>8
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