dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Feb 10 vh

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku puzzles
View previous topic :: View next topic  
Author Message
nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Sat Feb 09, 2008 11:08 pm    Post subject: Feb 10 vh Reply with quote

A little diversity can't hurt:

x-wing (removed 1)
xy-wing (removed 5) and
xyz-wing (removed 9)

All the wings having an x in their name...

Feb 10 - "x-day"? Shall I call the ex and send greetingss? Nah ...
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Johan



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

PostPosted: Sun Feb 10, 2008 12:09 am    Post subject: Reply with quote

Quote:
Shall I call the ex and send greetingss?


Better not nataraj, because my ex is useless Laughing

There is a useless [45-145-14] xyz-wing@ that takes out <9> in R4C8, after that just singles to the end.

The common digit <4> must appear in one of those three cells. These three possibile cells for placing <4> results in two pincer cells for digit <9>, either

R4C3=9(a) or R7C8=9(b), which eliminates <9> in R4C8.

a. R2C17=|4| => R2C3=|1| => R5C3=|6| => R4C3=|9|

b. R3C9={4} => R7C9={1} => R7C8={9}

Code:
+--------------------------+--------------------------+--------------------------+
| 249        8        3    | 5          1        49   | 246        26       7    |
||4|5@       6       |1|4  | 2          3        7    | 1|4|5@     8        9    |
| 25         149      7    | 8          6        49   | 235        235     @1{4} |
+--------------------------+--------------------------+--------------------------+
| 8          3      a 6|9| | 4          5        1    | 7          26-[9]   26   |
| 7          5        1|6| | 3          9        2    | 16         4        8    |
| 49         149      2    | 7          8        6    | 159        159      3    |
+--------------------------+--------------------------+--------------------------+
| 3          7        8    | 6          2        5    | 149      b 1{9}    {1}4  |
| 1          24       45   | 9          7        8    | 236        236      256  |
| 6          29       59   | 1          4        3    | 8          7        25   |
+--------------------------+--------------------------+--------------------------+
Back to top
View user's profile Send private message Send e-mail
storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sun Feb 10, 2008 5:26 am    Post subject: Reply with quote

you can put me down for:

x-wing on 1,
{4,5,9} xy-wing, pincers in r2c1, r6c7,

I made the basic eliminations after the xy-wing and...

I have a question at this point in the grid:

are the # marked squares a nice loop, or a unique loop??

r1c6 {4,9)
r1c1 {4,9}
r6c1 {4,9}
r6c2 {1,4,9}
r3c2 {1,4,9}
r3c6 {4,9}

Code:
   |---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 |   #49 |     8 |     3 ||     5 |     1 |   #49 ||    26 |    26 |     7
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r2 |     5 |     6 |    14 ||     2 |     3 |     7 ||    14 |     8 |     9
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r3 |     2 |  #149 |     7 ||     8 |     6 |   #49 ||    35 |    35 |    14
===========================||=======================||=======================
r4 |     8 |     3 |    69 ||     4 |     5 |     1 ||     7 |   269 |    26
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r5 |     7 |     5 |    16 ||     3 |     9 |     2 ||    16 |     4 |     8
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r6 |   #49 |  #149 |     2 ||     7 |     8 |     6 ||    59 |   159 |     3
===========================||=======================||=======================
r7 |     3 |     7 |     8 ||     6 |     2 |     5 ||    49 |    19 |    14
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r8 |     1 |    24 |    45 ||     9 |     7 |     8 ||   236 |   236 |   256
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r9 |     6 |    29 |    59 ||     1 |     4 |     3 ||     8 |     7 |    25
.............................................................................
Back to top
View user's profile Send private message
ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Sun Feb 10, 2008 1:19 pm    Post subject: Reply with quote

The 49's from a unique loop, but its useless, because we also know without it, that one of r36c2 must be 1.
Back to top
View user's profile Send private message
George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Feb 10, 2008 1:37 pm    Post subject: Another Maverik one Reply with quote

Every time I solve a VH via a Maverik solution, I repeat the process trying to find an "authorised solution".
The strange thing about this one is that after the Xwing I didn't need the XY wing that I used first time en route to the maverik process.

So in this grid after the X wing where I have not eliminated all the other more subtle candidates.
Code:

+------------------+--------+-----------------+
| 2459  8    3     | 5 1 49 | 2456  256  7    |
| 45    6    145   | 2 3 7  | 145   8    9    |
| 24579 1249 14579 | 8 6 49 | 12345 1235 1245 |
+------------------+--------+-----------------+
| 8     3    69    | 4 5 1  | 7     269  26   |
| 7     5    167   | 3 9 2  | 16    4    8    |
| 49    149  2     | 7 8 6  |  59   159  3    |
+------------------+--------+-----------------+
| 3     7    8     | 6 2 5  | 149   19   14   |
| 1     24   45    | 9 7 8  | 23456 2356 2456 |
| 6     29   59    | 1 4 3  | 8     7    25   |
+------------------+--------+-----------------+

[url=http://www.dailysudoku.com/sudoku/play.shtml?p=2459:8:3:5:1:49:2456:256:7:45:6:145:2:3:7:145:8:9:24579:1249:14579:8:6:49:12345:1235:1245:8:3:69:4:5:1:7:269:26:7:5:167:3:9:2:16:4:8:49:149:2:7:8:6: 59:159:3:3:7:8:6:2:5:149:19:14:1:24:45:9:7:8:23456:2356:2456:6:29:59:1:4:3:8:7:25:]Play this puzzle online[/url] at the Daily Sudoku site

I looked at the effect of r6c8 being 1 - If so it kills all the 9s in col 7 (via the 49 pair in box4 or the 19 in box 9) so r5c7 is 1 and that solves it.

THE POINT OF THIS IS THAT ONCE SEEN THIS IS SO OBVIOUS, BUT I COULDN'T FORCE IT INTO ONE OF THE STANDARD FORMS- CAN ANYONE HELP?
Back to top
View user's profile Send private message
Marty R.



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

PostPosted: Sun Feb 10, 2008 4:41 pm    Post subject: Reply with quote

I must've missed something. At any rate, after a couple of ERs, an X-Wing, W-Wing and two XY-Wings, I found myself at this position.

Code:
+------------+--------+--------------------+
| 249 8   3  | 5 1 49 | 246  26       7    |
| 5   6   14 | 2 3 7  | 14   8        9    |
| 249 149 7  | 8 6 49 | 2345 235      1245 |
+------------+--------+--------------------+
| 8   3   69 | 4 5 1  | 7    26-9APE  26   |
| 7   5   16 | 3 9 2  | 16   4        8    |
| 49  149 2  | 7 8 6  | 59   159APE   3    |
+------------+--------+--------------------+
| 3   7   8  | 6 2 5  | 49   19       14   |
| 1   24  45 | 9 7 8  | 2356 2356     256  |
| 6   29  59 | 1 4 3  | 8    7        25   |
+------------+--------+--------------------+


There is a rare (for me) Aligned Pair Exclusion, so marked in r46c8. The 9 is gone from r4c8 because 99 is invalid, 95 is excluded because of r6c7 and 91 because of r7c8. The puzzle is solved after removal of the 9.
Back to top
View user's profile Send private message
storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sun Feb 10, 2008 5:55 pm    Post subject: Reply with quote

Quote:
The 49's from a unique loop, but its useless, because we also know without it, that one of r36c2 must be 1.


Ravel,

thankyou,

so to make an elimination with that configuration, there would need to be another 1 in col 2. very cool. Idea
Back to top
View user's profile Send private message
Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS

PostPosted: Sun Feb 10, 2008 7:38 pm    Post subject: feb 10 VH Reply with quote

I had to use two xy-chains to eliminate the 9 in R6C1 and R6C7.

Not very sophisticated, but it worked.

Will a medusa solve it?

A VH worthy of the rating.

Earl
Back to top
View user's profile Send private message Send e-mail
TexCat



Joined: 07 Jul 2006
Posts: 32

PostPosted: Sun Feb 10, 2008 8:12 pm    Post subject: Reply with quote

I am stuck at this point, and can't manage to see any xyz wing. Can anyone help with my next step?
Code:

+-----------+--------+-------------+
| 49 8   3  | 5 1 49 | 26  26  7   |
| 5  6   14 | 2 3 7  | 14  8   9   |
| 2  149 7  | 8 6 49 | 35  35  14  |
+-----------+--------+-------------+
| 8  3   69 | 4 5 1  | 7   269 26  |
| 7  5   16 | 3 9 2  | 16  4   8   |
| 49 149 2  | 7 8 6  | 59  159 3   |
+-----------+--------+-------------+
| 3  7   8  | 6 2 5  | 49  19  14  |
| 1  24  45 | 9 7 8  | 236 236 256 |
| 6  29  59 | 1 4 3  | 8   7   25  |
+-----------+--------+-------------+

Play this puzzle online at the Daily Sudoku site

Edit: Marty, after posting this, I read up on your APE technique and now see how it works. Thanks.
Back to top
View user's profile Send private message
sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Sun Feb 10, 2008 9:41 pm    Post subject: Reply with quote

I reached this position too. An XYZ wing on 159 with pivot at R6C8 eliminates 9 at R4C8 and finishes it off. Phew!

Peter
Back to top
View user's profile Send private message Visit poster's website
Marty R.



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

PostPosted: Sun Feb 10, 2008 10:06 pm    Post subject: Reply with quote

Quote:
Edit: Marty, after posting this, I read up on your APE technique and now see how it works. Thanks.

And, of course, while doing the APE I never saw the wing, which the APE should have alerted me to.
Back to top
View user's profile Send private message
Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Sun Feb 10, 2008 10:20 pm    Post subject: Reply with quote

George,

Your <1> elimination is an AIC. I'll give the Eureka notation in a moment. But first...

Appropriately for you (since you're the "W" in W-Wing), your AIC is just a W-Wing variant. A {19} W-Wing with an external <9> strong link can be considered as the reduction of two ALSs: in this case, the two {19} bivalue ALSs.

In the case above, you have a {19} ALS plus a {149} ALS (in r6c12) which the external strongly-linked <9> (in c7) would reduce to a {14} "pair." (This "pair" would actually be a fixed <1> and a fixed <4>; but that doesn't matter.) The effect is exactly the same as a W-Wing. Think of it as a remote ALS pair where the external strong link activates the shared exclusive digit and then the shared common digit performs the elimination.

Now, for the Eureka moment...

First, let's pretend that r6c2 is a {19} bivalue and it is a conventional W-Wing. The Eureka would be:
(1)r6c8-(1=9)r6c2-(9=9)r67c7-(9=1)r7c8-(1)r6c8; r6c8<>1

Now, let's take the actual case above:
(1)r6c8-({14}=9})r6c12-(9=9)r67c7-(9=1)r7c8-(1)r6c8; r6c8<>1

Perhaps the Eureka notation makes the W-Wing-related structure clear... or vice-versa!

Note: That {149} ALS could also have been written "(1={49})r6c12". Either way is fine.
Back to top
View user's profile Send private message Visit poster's website
George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Feb 10, 2008 10:57 pm    Post subject: The AIC explanation Reply with quote

Thanks Asselus for the interpretation - All I can say other than this is Wow! - the formal explanation is certainly more difficult (for me) than the original explanation. However I don't suppose I should be surprised since I often find a very convoluted deduction that such and such a square is 4 , only to find a simple scan of the column (or row) explains the deduction so much more simply!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Daily Sudoku puzzles All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group