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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Thu Jan 24, 2008 1:34 am Post subject: jan 24 VH |
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| 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
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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
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| Posted: Thu Jan 24, 2008 2:03 am Post subject: |
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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 |
+-------------+------------+------------+
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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
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| Posted: Thu Jan 24, 2008 6:05 am Post subject: |
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| 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: 1048
Location: near Vienna, Austria
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| Posted: Thu Jan 24, 2008 6:41 am Post subject: |
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| 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
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| Posted: Thu Jan 24, 2008 9:09 am Post subject: |
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| nataraj wrote: | | XY-wing 57-25-27 and done. Did not consciously need an x-wing. |
Indeed - a nice, straightforward puzzle. 
John |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Thu Jan 24, 2008 9:25 am Post subject: |
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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: 1048
Location: near Vienna, Austria
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| Posted: Thu Jan 24, 2008 9:35 am Post subject: Re: jan 24 VH |
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| 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 |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Thu Jan 24, 2008 10:03 am Post subject: Re: jan 24 VH |
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| 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 |
well, if you are going to hand out extra points, how about a medusa solution?  |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Thu Jan 24, 2008 11:56 am Post subject: |
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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
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| Posted: Thu Jan 24, 2008 12:13 pm Post subject: |
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| 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: 1048
Location: near Vienna, Austria
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| Posted: Thu Jan 24, 2008 3:17 pm Post subject: Re: jan 24 VH |
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| storm_norm wrote: |
well, if you are going to hand out extra points, how about a medusa solution? |
right. And tomorrow I'll get a Caterpillar excavator to help the kids with their sand-cakes ... |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Thu Jan 24, 2008 3:56 pm Post subject: |
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| Code: |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . 7 . |
| . 7 . | . . . | 7 7 . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . 7 . | . . . | . 7 . |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+
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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
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| Posted: Thu Jan 24, 2008 4:23 pm Post subject: |
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| 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
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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: 32
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| Posted: Thu Jan 24, 2008 4:27 pm Post subject: |
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| 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
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| Posted: Thu Jan 24, 2008 6:21 pm Post subject: |
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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
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| Posted: Thu Jan 24, 2008 8:35 pm Post subject: |
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| 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
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| Posted: Fri Jan 25, 2008 1:28 pm Post subject: |
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| 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 – since I can’t perform the former. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jan 25, 2008 4:36 pm Post subject: |
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| 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
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| Posted: Fri Jan 25, 2008 5:16 pm Post subject: |
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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
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| Posted: Sun Jan 27, 2008 10:37 pm Post subject: |
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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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