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roaa
Joined: 18 Apr 2009
Posts: 112
Location: Sweden
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 Posted: Tue Mar 25, 2014 8:58 am Post subject: Mar 25 VH |
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| 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: 424
Location: Birmingham UK
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| Posted: Tue Mar 25, 2014 9:31 am Post subject: Mar 25 VH |
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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 |
+-----------------+-------------+--------------+
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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: 33
Location: New Orleans
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| Posted: Thu Mar 27, 2014 12:51 pm Post subject: Mar 25 VH |
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| 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: 5770
Location: Rochester, NY, USA
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| Posted: Sat Mar 29, 2014 12:01 am Post subject: |
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| 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: 207
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| Posted: Mon Mar 31, 2014 11:05 am Post subject: |
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| 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!)
on the other hand,
each of these
can be dropped
(and still have one answer) —
| Code: |
.........
.........
.......7.
......1..
.....1...
...4.....
.........
...9.....
.........
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required: either r4 1 or r8 9;
others can all be dropped.
here are the 2 puzzles with just 24 cells given —
— and yes, they are more challenging than the original puzzle |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Mar 31, 2014 11:29 pm Post subject: |
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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. 
| 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: 1834
Location: Northwest Arkansas USA
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| Posted: Mon Mar 31, 2014 11:47 pm Post subject: |
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| Marty R. wrote: | | Pat, I tried the first of your puzzles and am throwing in the towel. |
Good puzzle 
| 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: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Apr 15, 2014 10:31 am Post subject: Re: Mar 25 VH |
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| 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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