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Mar 25 VH

 
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roaa



Joined: 18 Apr 2009
Posts: 71
Location: Sweden

PostPosted: Tue Mar 25, 2014 8:58 am    Post subject: Mar 25 VH Reply with quote

Unusually few basic eliminations! But an XY-wing (278) forces r6c6=2, which is enough.
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hughwill



Joined: 05 Apr 2010
Posts: 167
Location: Birmingham UK

PostPosted: Tue Mar 25, 2014 9:31 am    Post subject: Mar 25 VH Reply with quote

After basics:
Code:

+-----------------+-------------+--------------+
| 12489 7    2469 | 138 1239 23 | 5    26 348  |
| 258   2356 256  | 38  7    4  | 9    26 1    |
| 12489 2349 249  | 5   1239 6  | 34   7  348  |
+-----------------+-------------+--------------+
| 7     8    246  | 36  236  9  | 1    5  24   |
| 3     245  245  | 7   258  1  | 248  9  6    |
| 59    569  1    | 4   56   28 | 28   3  7    |
+-----------------+-------------+--------------+
| 49    1    7    | 2   346  5  | 36   8  39   |
| 6     245  3    | 9   48   78 | 27   1  25   |
| 259   259  8    | 136 136  37 | 2367 4  2359 |
+-----------------+-------------+--------------+

Play this puzzle online at the Daily Sudoku site


Felt like more basics after the advanced move than before......
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rmireland



Joined: 21 Sep 2013
Posts: 7

PostPosted: Thu Mar 27, 2014 12:51 pm    Post subject: Mar 25 VH Reply with quote

Hi guys: I manually copy the puzzles to my homemade excel program to solve. When I did this one, I accidentally omitted the 3 from r6c8 and found the puzzle to be unsolvable (at least by me), so I figured the 3 might be essential rather than added only for symmetry. I restored the 3 and solved with the one XY. As an experiment I then tried omitting the symmetrical 8 in r4c2 and solved again. This time I found the puzzle to be a great one: several locked candidates, naked pairs, hidden pairs, two XY wings and a UR to finish. I am wondering if this incident is unique, or whether the desire for symmetry is making our puzzles less challenging in general. I don't know enough about creating the puzzles to know. Is there a thread for this?
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Marty R.



Joined: 12 Feb 2006
Posts: 5123
Location: Rochester, NY, USA

PostPosted: Sat Mar 29, 2014 12:01 am    Post subject: Reply with quote

Quote:
As an experiment I then tried omitting the symmetrical 8 in r4c2 and solved again. This time I found the puzzle to be a great one: several locked candidates, naked pairs, hidden pairs, two XY wings and a UR to finish. I am wondering if this incident is unique, or whether the desire for symmetry is making our puzzles less challenging in general. I don't know enough about creating the puzzles to know. Is there a thread for this?


I think you lucked out here. That 8 was necessary and in the course of your pairs, wings and URs that cell probably got set to 8.

I don't know anything about creating puzzles either, but I understand that asymmetrical puzzle offer a lot more opportunities.
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Pat



Joined: 23 Feb 2010
Posts: 165

PostPosted: Mon Mar 31, 2014 11:05 am    Post subject: Reply with quote

Marty R. wrote:
Quote:
tried omitting the 8 in r4c2

That 8 was necessary

yes,
dropping that 8 makes a
puzzle with 3 answers.
(and using "UR" is thus invalid!)

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Marty R.



Joined: 12 Feb 2006
Posts: 5123
Location: Rochester, NY, USA

PostPosted: Mon Mar 31, 2014 11:29 pm    Post subject: Reply with quote

Pat, I tried the first of your puzzles and am throwing in the towel. Too many cells with too many candidates. I didn't see anything productive and to continue would be a trial-and-error process of examining each cell to see if there was anything there. Embarassed

Code:

+-----------------+------------------+----------------+
| 1248 7     2469 | 138  12389  1238 | 5     26  348  |
| 258  2356  256  | 38   2378   4    | 9     267 1    |
| 1248 234   249  | 5    123789 6    | 348   27  348  |
+-----------------+------------------+----------------+
| 7    8     246  | 1346 1236   9    | 124   15  245  |
| 3    245   245  | 7    1258   128  | 1248  9   6    |
| 2459 24569 1    | 468  2568   28   | 248   3   7    |
+-----------------+------------------+----------------+
| 49   1     7    | 2    346    5    | 36    8   39   |
| 6    245   3    | 9    148    178  | 127   15  25   |
| 259  259   8    | 136  136    137  | 12367 4   2359 |
+-----------------+------------------+----------------+

Play this puzzle online at the Daily Sudoku site
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arkietech



Joined: 31 Jul 2008
Posts: 1708
Location: Northwest Arkansas USA

PostPosted: Mon Mar 31, 2014 11:47 pm    Post subject: Reply with quote

Marty R. wrote:
Pat, I tried the first of your puzzles and am throwing in the towel.


Good puzzle Very Happy

Code:
 *-----------*
 |.7.|...|5..|
 |...|..4|9.1|
 |...|5.6|...|
 |---+---+---|
 |78.|..9|...|
 |3..|7..|..6|
 |..1|...|.37|
 |---+---+---|
 |.1.|2.5|...|
 |6.3|9..|...|
 |..8|...|.4.|
 *-----------*
 *-----------------------------------------------------------------------------*
 | 1248    7       2469    | 138     12389  a1238    | 5       26      48-3    |
 | 258     2356    256     | 38      2378    4       | 9       267     1       |
 | 1248    234     249     | 5       12789-3 6       |b34      27      348     |
 |-------------------------+-------------------------+-------------------------|
 | 7       8       246     | 1346    1236    9       |b124     15      245     |
 | 3       245     245     | 7       1258   a128     |b1248    9       6       |
 | 2459    24569   1       | 468     2568   a28      |b248     3       7       |
 |-------------------------+-------------------------+-------------------------|
 | 49      1       7       | 2       346     5       | 36      8       39      |
 | 6       245     3       | 9       148    a178     |b127     15      25      |
 | 259     259     8       | 136     136     137     | 12367   4       2359    |
 *-----------------------------------------------------------------------------*
(3=7)r1568c6-(7=3)r34568c7 => -3r1c9,r3c5; lclste
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Tue Apr 15, 2014 10:31 am    Post subject: Re: Mar 25 VH Reply with quote

rmireland wrote:
Hi guys: I manually copy the puzzles to my homemade excel program to solve. When I did this one, I accidentally omitted the 3 from r6c8 and found the puzzle to be unsolvable (at least by me), so I figured the 3 might be essential rather than added only for symmetry. I restored the 3 and solved with the one XY. As an experiment I then tried omitting the symmetrical 8 in r4c2 and solved again. This time I found the puzzle to be a great one: several locked candidates, naked pairs, hidden pairs, two XY wings and a UR to finish. I am wondering if this incident is unique, or whether the desire for symmetry is making our puzzles less challenging in general. I don't know enough about creating the puzzles to know. Is there a thread for this?


There are various techniques to create puzzles. Do a search on
sudoku programming
sudoku puzzle maker
etc

Many of those sites have been lost.

Menneske generates "minimal" puzzles which are not symmetric. Each given value is essential for a valid puzzle. Adding clues to make the initial puzzle symmetric will almost always make the puzzle easier.

Keith
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