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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Sun Feb 26, 2012 12:51 am Post subject: Diabolical, February 24 |
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These are generally fairly easy for me, but not this one. I haven't made a move, but will look at it some more.
| Code: |
+----------------+---------+--------------+
| 678 267 67 | 9 4 1 | 5 237 378 |
| 48 9 5 | 3 2 7 | 1 6 48 |
| 3 1247 147 | 5 8 6 | 27 247 9 |
+----------------+---------+--------------+
| 167 1567 1679 | 8 13 2 | 4 3579 367 |
| 2 3 79 | 4 6 5 | 79 8 1 |
| 146 1456 8 | 7 13 9 | 236 235 36 |
+----------------+---------+--------------+
| 5 467 467 | 1 9 34 | 8 347 2 |
| 49 8 2 | 6 7 34 | 39 1 5 |
| 1479 147 3 | 2 5 8 | 679 479 467 |
+----------------+---------+--------------+
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Play this puzzle online at the Daily Sudoku site |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Sun Feb 26, 2012 3:14 am Post subject: |
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Using nice loop notation that existed at the time b/b-plots were introduced:
r5c3 -9- r4c3 =9= r4c9 =5= r6c8 =2= r6c7 -2- r4c7 -7- r5c7 =7= r5c3 ==> r5c3<>9, ste
One strong link is a bivalue (at r4c7), the rest are bilocals. I doubt if this is the shortest chain that cracks the puzzle. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Feb 26, 2012 5:49 am Post subject: |
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| Thank you. I'm really surprised that this puzzle requires such an advanced solution based on the history. |
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JC Van Hay
Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium
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| Posted: Sun Feb 26, 2012 8:21 am Post subject: |
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Another view of Ronk's solution :
In the B/B-Plot, the first most interesting cell is r4c8, where a V-shape cluster of 3 5s and a Y-shape cluster of 4 9s are weakly coupled, the vertices of these clusters being in r4c8. Such an observation prompts an eventual elimination of 5r4c8 or 9r4c8.
In fact, if r4c8=9, then r6c8=5 and r5c7=7, r3c7=2; and there is no place for a 2 in row 6. Therefore, r4c8<>9.
The corresponding AIC is 5r4c8=(5-2)r6c8=2r6c7-(2=7)r3c7-(7=9)r5c7 => -9r4c8 (because r4c8=5 and/or r5c7=9)
After this 4-SIS AIC, the puzzle solves with singles only to the end.
Note : it's time to use AIC when the puzzle is rated above SE7.0 !
JC |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Sun Feb 26, 2012 9:16 am Post subject: |
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| Code: | r5c7=7 -> r3c7=2 -> r6c7<>2
-> r4c8<>5 -> r6c8=25 |
A controversial solution?
/SudoQ |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Sun Feb 26, 2012 11:36 am Post subject: |
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| SudoQ wrote: | | Code: | r5c7=7 -> r3c7=2 -> r6c7<>2
-> r4c8<>5 -> r6c8=25 |
A controversial solution? |
No, but few like inductive logic; too much like "crash & burn."  |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Feb 26, 2012 4:55 pm Post subject: |
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| SudoQ wrote: | | Code: | | r5c7=7 -> r3c7=2 -> r6c7<2> r4c8<5> r6c8=25 |
A controversial solution?
/SudoQ |
I did not fully understand your notation, but it is possible to create an AIC using the same general cells.
(7=2)r3c7-als(2=36)r6c79-(36=7)r4c9; r5c7<>9
Ted |
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ronk
Joined: 07 May 2006
Posts: 398
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| Posted: Sun Feb 26, 2012 9:58 pm Post subject: |
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| tlanglet wrote: | | SudoQ wrote: | | Code: | | r5c7=7 -> r3c7=2 -> r6c7<2> r4c8<5> r6c8=25 |
A controversial solution? |
I did not fully understand your notation, but it is possible to create an AIC using the same general cells.
(7=2)r3c7-als(2=36)r6c79-(36=7)r4c9; r5c7<>9 |
Pretty sure SudoQ means "assert r5c7=7, then r6c8 must hold both <2> and <5>, an impossibility." IOW as an AIC ...
(7=2)r3c7 - (2)r6c7 = (2-5)r6c8 = (5-9)r4c8 = (9)r5c7 ==> r5c7<>7 |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Sun Feb 26, 2012 11:36 pm Post subject: |
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| ronk wrote: | | Pretty sure SudoQ means "assert r5c7=7, then r6c8 must hold both <2> and <5>, an impossibility." |
That's correct!
| ronk wrote: | IOW as an AIC ...
(7=2)r3c7 - (2)r6c7 = (2-5)r6c8 = (5-9)r4c8 = (9)r5c7 ==> r5c7<>7 |
Since I haven't been able to learn how AIC works,
I can't tell how hard it is to frame your expressions.
If it was possible to convert my solution to AIC mechanical,
would it then be any quality difference between the solutions?
/SudoQ |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Wed Feb 29, 2012 4:52 pm Post subject: |
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| SudoQ wrote: | If it was possible to convert my solution to AIC mechanical,
would it then be any quality difference between the solutions? |
Almost all the solutions you have posted in recent months have had some similar characteristics. Apart from the lack of detail in the chains and networks you present, one thing does stand out.
The solutions start with either a bivalue (only two values left in a cell) or a bilocal (only two appearances of a digit within a house.) In either case, only one value can be true, quite obviously.
The digit that can’t be true is then plugged in and followed to an inevitable contradiction. The disparity is offered as a solution, usually with a comment like, “It is easy to show that…”
You are not the first to have noticed that this method works extremely well. Many have wondered out loud why anyone would jump through such elaborate hoops to solve puzzles otherwise when this panacea sits right under their noses. There are countless more in your camp than in the hoop-jumpers'.
This forum and others like it only exist because there are folks who have chosen to not solve puzzles in certain ways, including making assumptions about a truth. If their aim was just to solve puzzles this discussion would not be taking place.
Heck, I’d just load it up into Simple Sudoku, plug in a value and hold F11 |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Fri Mar 02, 2012 4:48 pm Post subject: |
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Hi Luke,
and thanks for your comments!
| Luke451 wrote: | | In either case, only one value can be true |
This is in itself true, but may not be displayed (in a reasonably simple way).
In addition, I first try to find candidates that can be eliminated regardless of which option is true.
In this process, it sometimes appears that one option is incorrect.
I have chosen not to throw away this information.
| Luke451 wrote: | | usually with a comment like, “It is easy to show that… |
(This I have only done ones!)
| Luke451 wrote: | | lack of detail in the chains and networks |
This may be true... and I cannot follow solutions like this:
| Code: | XY-Wing (297); r7c9, r9c3<>7
Multi-coloring; r2c3<>4
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| Luke451 wrote: | | You are not the first to have noticed that this method works extremely well. |
This is true. However, I have been surprised that no method list I have seen, contains this method, or that it is only mentioned in general terms in passing.
If you want to help beginners to solve difficult puzzles, you could start by desribe this method (and then explain why it should not be used!).
| Luke451 wrote: | | .. because there are folks who have chosen to not solve puzzles in certain ways |
I respect that, and if there are any rules in this forum about methods that may not be used, please let me know.
| Luke451 wrote: | | .. I’d just load it up into Simple Sudoku, plug in a value and hold F11. |
But, I guess this does not give anything that can be presented here!?
Finally...
I think this is a nice forum, with a (as a rule) friendly and unpretentious atmosphere.
I also think that the level of the puzzles are good, because they can be solved entirely by hand, by the pros, and for others, with a little help from computers.
It also seems to be an unspoken competition to find solutions with few steps (preferably one), rather than to use methods in a given difficulty order.
Since I tend to cheat, I have tried to settle with posting my solution when I think they provides an alternative to those already posted.
In a few cases they may have raised some curiosity.
If so, maybe this was not a completely useless activity.
/SudoQ |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Mar 02, 2012 5:13 pm Post subject: |
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Luke451 wrote:
.. because there are folks who have chosen to not solve puzzles in certain ways
I respect that, and if there are any rules in this forum about methods that may not be used, please let me know. |
There are no rules. Many of us take this overly seriously, but let's face it, it's only a game. Puzzles are there for our amusement and can be used by us in any way that we prefer.
I suppose we post solutions for a number of reasons, perhaps to inform, to educate, to satisfy our urge to post something, or whatever.
But there are no rules about what methods may be used. Not everyone cares for all methods that can be used to solve puzzles, but we're free to post them as we please and people are equally free to react to or comment on them as they please.
As far as I'm concerned, all players are welcome, at all skill levels, using any or all methods that they like. The more the merrier. |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Sat Mar 03, 2012 8:53 am Post subject: |
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No one who plays this game has ever done anything wrong if they had a good time doing so. No one can tell anyone else that the legal method they used to reach a solution should not be used. If the aim is to solve the puzzle and the puzzle ends up solved in a way that satisfies the solver, it’s a win for that solver.
Of all the games I can think of , this one has the greatest complexity given the simplicity of its rules. From the most basic of constraints springs a surprising depth of field. How deeply one decides to probe the depths is purely an individual choice.
SudoQ, I’m happy to see your contributions. You’ve enlivened the discussions around here and I hope you continue doing so. Probing the “depths” won’t provide any different solutions to puzzles than the ones you have already utilized.
If you have the inclination, you could look into why other players often offer alternatives to your solutions. It may lead you down a rabbit hole, but it could also enhance your enjoyment of the game. |
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