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jan 24 VH

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Jan 24, 2008 1:34 am    Post subject: jan 24 VH Reply with quote

Code:
2       458     458     | 9       46      7       | 1       56      3
6       3       57      | 28      12      18      | 9       57      4
9       47      1       | 5       46      3       | 267     267     8
---------------------------------------------------------------------
4       6       25      | 7       12      58      | 3       18      9
8       27      3       | 24      9       14      | 5       17      6
1       579     579     | 3       58      6       | 78      4       2
---------------------------------------------------------------------
7       1       89      | 6       3       2       | 4       89      5
5       2489    6       | 48      7       489     | 28      3       1
3       2489    2489    | 1       58      4589    | 268     2689    7


is coloring on 7 the fastest to a solution??
if not, as I was scanning for possible xy-wings, I found countless xy-chains. some long, some short.
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prakash



Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA

PostPosted: Thu Jan 24, 2008 2:03 am    Post subject: Reply with quote

The xy wing with pivot at R4c3 (257)
Code:

+-------------+------------+------------+
| 2 458  458  | 9  46 7    | 1   56   3 |
| 6 3    57   | 28 12 18   | 9   57   4 |
| 9 4-7   1    | 5  46 3    | 267 267  8 |
+-------------+------------+------------+
| 4 6    25   | 7  12 158  | 3   18   9 |
| 8 27   3    | 24 9  14   | 5   17   6 |
| 1 579  579  | 3  58 6    | 78  4    2 |
+-------------+------------+------------+
| 7 1    89   | 6  3  2    | 4   89   5 |
| 5 2489 6    | 48 7  489  | 28  3    1 |
| 3 2489 2489 | 1  58 4589 | 268 2689 7 |
+-------------+------------+------------+


This got me to:
Code:

+------------+------------+----------+
| 2 58  58   | 9  4  7    | 1  6   3 |
| 6 3   7    | 28 12 18   | 9  5   4 |
| 9 4   1    | 5  6  3    | 27 27  8 |
+------------+------------+----------+
| 4 6   25   | 7  12 158  | 3  18  9 |
| 8 27  3    | 24 9  14   | 5  17  6 |
| 1 579 59   | 3  58 6    | 78 4   2 |
+------------+------------+----------+
| 7 1   89   | 6  3  2    | 4  89  5 |
| 5 289 6    | 48 7  489  | 28 3   1 |
| 3 289 2489 | 1  58 4589 | 6  289 7 |
+------------+------------+----------+
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Marty R.



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

PostPosted: Thu Jan 24, 2008 6:05 am    Post subject: Reply with quote

Quote:
is coloring on 7 the fastest to a solution??

Maybe six of one and a half-dozen of the other. It appears from a superficial look that the coloring accomplishes pretty much the same thing as the 25-27-57 XY-Wing I used, after which an X-Wing on 5 finished it off.
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nataraj



Joined: 03 Aug 2007
Posts: 1047
Location: near Vienna, Austria

PostPosted: Thu Jan 24, 2008 6:41 am    Post subject: Reply with quote

XY-wing 57-25-27 and done. Did not consciously need an x-wing.
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andras



Joined: 31 Oct 2007
Posts: 56
Location: Mid Wales

PostPosted: Thu Jan 24, 2008 9:09 am    Post subject: Reply with quote

nataraj wrote:
XY-wing 57-25-27 and done. Did not consciously need an x-wing.


Indeed - a nice, straightforward puzzle. Smile

John
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Johan



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

PostPosted: Thu Jan 24, 2008 9:25 am    Post subject: Reply with quote

An alternative way to solve this one may be a cumbersome route, exploring a potential [26] DP(Deadly Pattern) in R39C78, nevertheless analysing those UR's

can be very helpful breaking a puzzle wide open.

The grid after basics shows a potential [26] DP* in R39C78, only three possible ways for avoiding this DP :

1. R9C78=|8| => R9C5=5 => R6C5=8 => R6C7=7 => R5C2=7 => R3C2 ≠ 7

2. R3C78=[7] => R3C2 ≠ 7

3. R9C8={9} => R7C8=8 => R7C3=9 => R4C3=2 => R5C2=7 => R3C2 ≠ 7


Now digit <4> can be placed in R3C2, that succumbs the puzzle.
Code:

+--------------------------+--------------------------+--------------------------+
| 2       458        458   | 9         46       7     | 1         56         3   |
| 6       3          57    | 28        12       18    | 9         57         4   |
| 9       47         1     | 5         46       3     |*26[7]    *26[7]      8   |
+--------------------------+--------------------------+--------------------------+
| 4       6         {2}5   | 7         12       58    | 3         18         9   |
| 8       2{|7|}     3     | 24        9        14    | 5         17         6   |
| 1       579        579   | 3         5|8|     6     ||7|8       4          2   |
+--------------------------+--------------------------+--------------------------+
| 7       1          8{9}  | 6         3        2     | 4        {8}9        5   |
| 5       2489       6     | 48        7        489   | 28        3          1   |
| 3       2489       2489  | 1        |5|8      4589  |*26|8|    *26|8|{9}   7   |
+--------------------------+--------------------------+--------------------------+
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nataraj



Joined: 03 Aug 2007
Posts: 1047
Location: near Vienna, Austria

PostPosted: Thu Jan 24, 2008 9:35 am    Post subject: Re: jan 24 VH Reply with quote

storm_norm wrote:

is coloring on 7 the fastest to a solution?


Since both coloring on 7 (7:-r2c3=r2c8-r3c7=r6c7-r6c3=r2c3-) and the xy-wing solve the same cell r3c2=4, it obviously depends on what one tries first. I just happened to see the xy-wing before I started scanning for single candidate patterns.

Both being equal in terms of speed=number of moves needed, in this case (the coloring elimination was more involved than just a simple x-wing) I'd give an extra point to xy-wing for ease of use and an extra point to coloring for exotic appeal Smile
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Jan 24, 2008 10:03 am    Post subject: Re: jan 24 VH Reply with quote

nataraj wrote:
storm_norm wrote:

is coloring on 7 the fastest to a solution?


Since both coloring on 7 (7:-r2c3=r2c8-r3c7=r6c7-r6c3=r2c3-) and the xy-wing solve the same cell r3c2=4, it obviously depends on what one tries first. I just happened to see the xy-wing before I started scanning for single candidate patterns.

Both being equal in terms of speed=number of moves needed, in this case (the coloring elimination was more involved than just a simple x-wing) I'd give an extra point to xy-wing for ease of use and an extra point to coloring for exotic appeal Smile


well, if you are going to hand out extra points, how about a medusa solution? Laughing Laughing Laughing
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Asellus



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

PostPosted: Thu Jan 24, 2008 11:56 am    Post subject: Reply with quote

prakash,

In your first grid, there is a {124} naked triple in box 5, so <1> can be removed from r4c6.

In your second grid, after applying the XY-Wing, there is a {589} naked triple in c3 that determines r4c3=2 and r9c3=4, and more follows, solving the puzzle. So, only that XY-Wing was necessary for this one.
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Thu Jan 24, 2008 12:13 pm    Post subject: Reply with quote

Also the w-wing 18 solves the puzzle (in the moment they jump into my eyes).
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nataraj



Joined: 03 Aug 2007
Posts: 1047
Location: near Vienna, Austria

PostPosted: Thu Jan 24, 2008 3:17 pm    Post subject: Re: jan 24 VH Reply with quote

storm_norm wrote:


well, if you are going to hand out extra points, how about a medusa solution? Laughing Laughing Laughing


right. And tomorrow I'll get a Caterpillar excavator to help the kids with their sand-cakes ... Laughing
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Thu Jan 24, 2008 3:56 pm    Post subject: Reply with quote

Code:
            
+-------+-------+-------+   
| . . . | . . . | . . . |   
| . . . | . . . | . 7 . |   
| . 7 . | . . . | 7 7 . |   
+-------+-------+-------+   
| . . . | . . . | . . . |   
| . 7 . | . . . | . 7 . |   
| . . . | . . . | . . . |   
+-------+-------+-------+   
| . . . | . . . | . . . |   
| . . . | . . . | . . . |   
| . . . | . . . | . . . |
+-------+-------+-------+


Near the start I found this ER solution. There's an L shape hinge in Box 3. Doesn't matter which of the two candidates is the <7> in R5; R3C2 cannot be a <7>. A lot of basics after that - but nothing fancy.

Things have been very slow on the Sudoku.com sites lately. Is it just my equipment that's slow. It been very cold in Canada lately.
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Thu Jan 24, 2008 4:23 pm    Post subject: Reply with quote

nataraj wrote:
Caterpillar excavator

What about this one ?
Code:
2       458     458     | 9       46      7       | 1       56      3
6       3       57      | 28      12      18      | 9       57      4
9       47      1       | 5       46      3       | 267    #2-67    8
---------------------------------------------------------------------
4       6       25      | 7       12      58      | 3       18      9
8      #27      3       | 24      9       14      | 5       17      6
1       579     579     | 3       58      6       | 78      4       2
---------------------------------------------------------------------
7       1       89      | 6       3       2       | 4       89      5
5       2489    6       | 48      7       489     | 28      3       1
3       2489    2489    | 1       58      4589    |-268     2689    7

In the 26 UR (with the strong links for 2 and 6) we can directly eliminate 2 from r9c7 and 6 from r3c8 .

The latter gives the marked two pairs 27 with
r3c8=7 => r5c8<>7 => r5c2=7
r5c2=7 => (r6c23<>7 => r6c7=7 => r3c7<>7) and (r3c2<>7 => r2c3=7 => r2c8<>7) => r3c8=7
That means we have an M-wing.
With the strong link for 7 in r5 r3c7 or r5c7 must be 7 and therefore r2c8<>7. Singles follow.
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TexCat



Joined: 07 Jul 2006
Posts: 31

PostPosted: Thu Jan 24, 2008 4:27 pm    Post subject: Reply with quote

And I found the skyscraper of 7s in columns 3 and 7 to also eliminate the 7 from the same R3C2 as well as R2C8.
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Johan



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

PostPosted: Thu Jan 24, 2008 6:21 pm    Post subject: Reply with quote

Another one step move is a finned x-wing* on <7> in R36C27 that takes out <7> in R6C3, either the fin (F) is true or the x-wing, in both cases the <7> in
R6C3 is toast, after that just singles.
Code:

+--------------------------+--------------------------+--------------------------+
| 2       458       458    | 9         46       7     | 1         56         3   |
| 6       3         57     | 28        12       18    | 9         57         4   |
| 9      *47        1      | 5         46       3     |*267       267        8   |
+--------------------------+--------------------------+--------------------------+
| 4       6         25     | 7         12       58    | 3         18         9   |
| 8     F 27        3      | 24        9        14    | 5         17         6   |
| 1      *579       5-[7]9 | 3         58       6     |*78        4          2   |
+--------------------------+--------------------------+--------------------------+
| 7       1         89     | 6         3        2     | 4         89         5   |
| 5       2489      6      | 48        7        489   | 28        3          1   |
| 3       2489      2489   | 1         58       4589  | 268       2689       7   |
+--------------------------+--------------------------+--------------------------+
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Victor



Joined: 29 Sep 2005
Posts: 207
Location: NI

PostPosted: Thu Jan 24, 2008 8:35 pm    Post subject: Reply with quote

Could do with a style judge such as they have in dancing competitions! - x pts for an ER, y pts for W-wing etc. 0 for my simple XY-wing I guess.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Fri Jan 25, 2008 1:28 pm    Post subject: Reply with quote

Quote:
Could do with a style judge such as they have in dancing competitions!

Good idea. The zero points should go to any trial and error solution. But the question is: should the highest points go to those performances that use complex moves such as Medusas, type2 w-wings and finned wings. Or should the style judge look for simple elegance (like the ER shown above). I would say the latter Ė since I canít perform the former.
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Marty R.



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

PostPosted: Fri Jan 25, 2008 4:36 pm    Post subject: Reply with quote

Quote:
The zero points should go to any trial and error solution.

Ah, but the devil is in the details. Can anyone define T&E? Or is it like pornography, about which U.S. Supreme Court Justice Stewart said, "I can't define it, but I know it when I see it"?
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Fri Jan 25, 2008 5:16 pm    Post subject: Reply with quote

T&E in its purest form is how I used to solve the VHs before I became clever. I'd go to the first available pair - e.g. in the above case a 5 and 7 and say "let it be a 5 - and if that dont work - it's a 7". I actually solved them that way in less time than I do now. But where's the respect.

As for porno I'll refrain from the comparison to T&E.
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DennyOR



Joined: 12 Sep 2007
Posts: 33
Location: Portland, Oregon

PostPosted: Sun Jan 27, 2008 10:37 pm    Post subject: Reply with quote

From storm_norm's position the xy chain (r4c8) 81-12-24-41-18 (r2c6) also solves the puzzle. I always look for xy chains first (including xy wings which are chains of 3) because to me they seem less tedious and more fun than other advanced techniques. The majority of the very hards can be solved with one or more xy chains.

Denny
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