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1 April VH

 
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Rocky Mozell



Joined: 28 Jul 2010
Posts: 21
Location: Boston, MA

PostPosted: Fri Apr 01, 2011 1:22 pm    Post subject: 1 April VH Reply with quote

249 XY-wing with pivot r7c1. How is this the first post?
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eddieg



Joined: 12 Jan 2006
Posts: 47
Location: San Diego, CA USA

PostPosted: Fri Apr 01, 2011 2:57 pm    Post subject: Reply with quote

I never post, but always work the VH puzzles. Love this site.
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williamholiday



Joined: 01 Apr 2011
Posts: 6

PostPosted: Fri Apr 01, 2011 3:44 pm    Post subject: Today's puzzle Reply with quote

Hi,
New member here. Been doing the puzzles @ DS for a while and now I want to talk a little strategy, if that's OK?

Today's VH(4/1). After getting about half way and facing a combination that I couldn't "compute" but that I hoped would "trigger" the remainder, I took a screenshot, and ran the first option. It didn't work but after reconstructing the board, the second resulted in a solve. This is the second time I've solved the VH level, though sometimes an H will stump me, and both times I've had to go to what is essentially, trial and error.

Is "hit or miss" a typical technique for anybody else?

-william.
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Marty R.



Joined: 12 Feb 2006
Posts: 5064
Location: Rochester, NY, USA

PostPosted: Fri Apr 01, 2011 6:03 pm    Post subject: Reply with quote

This puzzle seemed to have a busier grid and required a lot more basics work than most. I also used the 492 XY-Wing.

William, welcome to the forum.

Quote:
Is "hit or miss" a typical technique for anybody else?

If by "hit or miss" you mean trial-and-error, most players here try to avoid it, although there is not always agreement on whether a given technique is actually trial-and-error.

Most players find it more satisfying to use techniques based on spotting patterns. However, all puzzles are here for our amusement and whatever people find enjoyable is fine.

If you have any questions don't hesitate to ask, as there are a number of people glad to help others.
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williamholiday



Joined: 01 Apr 2011
Posts: 6

PostPosted: Fri Apr 01, 2011 9:17 pm    Post subject: not exactly "hit or miss" Reply with quote

Hi Marty,

Thanks for the reply.

Most of the time there's a eureka moment. A day or so ago, on a Hard puzzle, the cell(s) that tripped the rest of the puzzle was an either-or across two of the 9 grids rather than within one, if you know what I mean. It was fun to work up to that point and then spot that.

On today's puzzle I never found the place where the exception proved the puzzle. I got to a point where one cell was a one and another was a three and I solved for both by entering numbers rather than by looking and figuring. I just wondered if others solved the VH class puzzles this way sometimes. On both of the VH ones that I finished I used this kludge, I had to enter numbers on the sheet, I couldn't do the logic without writing.

all the best,
-william.
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Fri Apr 01, 2011 10:56 pm    Post subject: Reply with quote

William,

I think you mean "pencil marks", which is when you note the possible candidates in unsolved cells.

I always use pencil marks on this site's Very Hard puzzles. As a personal challenge, I do not use them on Hard puzzles.

People use all kinds of rules to make easy puzzles more challenging. For example, you have to solve all the cells in a block before moving on to another block.

By the way, you will see people use a number of techniques, but this site's Very Hard puzzles can be solved with only three "advanced" patterns: X-wing, XY-wing, and XYZ-wing. You can look up those terms on Google, or go to sudopedia.org.

Welcome to the forum! The crowd here is knowledgeable, helpful and courteous.

Best wishes,

Keith
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williamholiday



Joined: 01 Apr 2011
Posts: 6

PostPosted: Fri Apr 01, 2011 11:53 pm    Post subject: Got it now. Thanks! Reply with quote

Ladies and Gentlemen, Keith,

I thought I had taken a short cut and I'm now I'm sure(but I was soooo proud of finishing, I had to find out 8-)

I'm going to do a little research, thanks for the pointer. I particularly like the quality and play at this site and of course, the community is stellar!

-william.
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Sat Apr 02, 2011 2:06 am    Post subject: Reply with quote

William,

Remember that this site is a wonderful place for tutorials. Don't wait for the new puzzles. For each previous Very Hard puzzle, there is a discussion on how to solve it*. And, there is almost never one solution path.

So, please explore the discussions of past puzzles.

Keith

* Except, a few years ago, some discussions for a period of a year or so were lost in a system crash.
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Ema Nymton



Joined: 17 Apr 2009
Posts: 83

PostPosted: Sat Apr 02, 2011 11:15 am    Post subject: Reply with quote

.

Being a visual learner that I am, after the basics I found myself with this puzzle:

Code:

+------------+-----------------+------------+
| 5  3489 39 | 4689 2689 2468  | 468 1   7  |
| 6  248  24 | 7    5    1     | 48  3   9  |
| 7  489  1  | 4689 2689 3     | 5   268 26 |
+------------+-----------------+------------+
| 2  6    8  | 3    1    9     | 7   4   5  |
| 19 39   7  | 2    4    5     | 68  68  13 |
| 14 345  35 | 68   7    68    | 2   9   13 |
+------------+-----------------+------------+
|A49 2459 6  | 1   B29   247   | 3   257 8  |
| 3  1   C24 | 5    268  24678 | 9   267 26 |
| 8  7    59 |D69   3   E26    | 1   256 4  |
+------------+-----------------+------------+
................................................Box 8

Solving this puzzle can take on two separate walks:

1) Alignment of cells ABC eliminates the '2' from r7c2; thus C = '2.'

and/or

2) Alignment of cells BDE eliminates '2' & '6' from all other cells in box 8; thus r8c5 = '8.'


Ema Nymton
.
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Marty R.



Joined: 12 Feb 2006
Posts: 5064
Location: Rochester, NY, USA

PostPosted: Sat Apr 02, 2011 3:39 pm    Post subject: Reply with quote

Quote:
Being a visual learner that I am, after the basics I found myself with this puzzle:

Ema,

Most players consider basics to consist of subsets (pairs, triples, quads, etc.) and locked candidates, also known as box-line interactions.

Thus your BDE is a naked triple, which is considered basic. This was my post-basics grid and I needed the XY-Wing (ABC) to solve it.

Code:

+------------+------------+------------+
| 5  3489 39 | 489 269 28 | 468 1   7  |
| 6  248  24 | 7   5   1  | 48  3   9  |
| 7  489  1  | 489 69  3  | 5   268 26 |
+------------+------------+------------+
| 2  6    8  | 3   1   9  | 7   4   5  |
| 19 39   7  | 2   4   5  | 68  68  13 |
| 14 345  35 | 68  7   68 | 2   9   13 |
+------------+------------+------------+
| 49 2459 6  | 1   29  47 | 3   257 8  |
| 3  1    24 | 5   8   47 | 9   267 26 |
| 8  7    59 | 69  3   26 | 1   25  4  |
+------------+------------+------------+

Play this puzzle online at the Daily Sudoku site
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williamholiday



Joined: 01 Apr 2011
Posts: 6

PostPosted: Sun Apr 03, 2011 4:52 am    Post subject: Reply with quote

Thanks again Kieth and Ema, your graphic is exactly where I was when I ran out of techniques and turned to blunt force solving. I took a look at the sudopedia and expect to integrate the xyz-wing as time goes by. That combination of 3 numbers crops up a lot and I didn't know that it provided eliminations. That was the core question I initially posed "What do folks do when they run out of tools?" And now I know a new one.

I took a look at the first post again and it make sense after this little discussion.

all the best
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