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ProfessorF
What's a life?
Joined: Thu Apr 23, 2009 7:56 pm Posts: 12030
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http://www.cube20.org/ |  |  |  | Quote: Every position of Rubik's Cube™ can be solved in twenty moves or less. With about 35 CPU-years of idle computer time donated by Google, a team of researchers has essentially solved every position of the Rubik's Cube™, and shown that no position requires more than twenty moves.
Every solver of the Cube uses an algorithm, which is a sequence of steps for solving the Cube. One algorithm might use a sequence of moves to solve the top face, then another sequence of moves to position the middle edges, and so on. There are many different algorithms, varying in complexity and number of moves required, but those that can be memorized by a mortal typically require more than forty moves.
One may suppose God would use a much more efficient algorithm, one that always uses the shortest sequence of moves; this is known as God's Algorithm. The number of moves this algorithm would take in the worst case is called God's Number. At long last, God's Number has been shown to be 20.
It took fifteen years after the introduction of the Cube to find the first position that provably requires twenty moves to solve; it is appropriate that fifteen years after that, we prove that twenty moves suffice for all positions.
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Wed Aug 11, 2010 10:55 am |
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Amnesia10
Legend
Joined: Fri Apr 24, 2009 2:02 am Posts: 29240 Location: Guantanamo Bay (thanks bobbdobbs)
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Could it be 42? the answer to life the universe and everything?
_________________Do concentrate, 007... "You are gifted. Mine is bordering on seven seconds." https://www.dropbox.com/referrals/NTg5MzczNTkhttp://astore.amazon.co.uk/wwwx404couk-21
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Wed Aug 11, 2010 11:22 am |
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l3v1ck
What's a life?
Joined: Fri Apr 24, 2009 10:21 am Posts: 12700 Location: The Right Side of the Pennines (metaphorically & geographically)
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In my world it's not solvable at all...... ever. I have never been able to finish a Rubiks Cube. Annoyingly my mate Steve can do them in less than a minute every time.
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Wed Aug 11, 2010 2:35 pm |
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rustybucket
I haven't seen my friends in so long
Joined: Thu Jun 18, 2009 5:10 pm Posts: 5836
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I probably could but.... ... why? It's the same as Sudoku and Big Brother for me - not entertaining in the least
_________________Jim
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Wed Aug 11, 2010 3:29 pm |
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finlay666
Spends far too much time on here
Joined: Thu Apr 23, 2009 9:40 pm Posts: 4876 Location: Newcastle
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If it's the same algorithm it was developed years ago by a kid....
Someone on my course did a graphical one for their FYP... not sure why it's not like the algorithm was new or anything
_________________TwitterCharlie Brooker: Macs are glorified Fisher-Price activity centres for adults; computers for scaredy cats too nervous to learn how proper computers work; computers for people who earnestly believe in feng shui.
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Wed Aug 11, 2010 8:08 pm |
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Fogmeister
I haven't seen my friends in so long
Joined: Thu Apr 23, 2009 7:35 pm Posts: 6580 Location: Getting there
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I have been able to solve them within a minute in the past (about a year ago in fact) but if you don't keep doing it you lose the algorithms and forget how to solve it from certain cases.
My record is about 42 seconds ish. (That's using a randomly generated cypher sequence to mix up the cube in the first place).
I wonder if it will ever get moved down to 19?
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Wed Aug 11, 2010 8:19 pm |
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Fogmeister
I haven't seen my friends in so long
Joined: Thu Apr 23, 2009 7:35 pm Posts: 6580 Location: Getting there
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Oh, having re-read the OP I can see that they have mathematically proved that at least one starting position requires at least 20 moves.
So 19 isn't going to happen.
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Wed Aug 11, 2010 8:20 pm |
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paulzolo
What's a life?
Joined: Thu Apr 23, 2009 6:27 pm Posts: 12251
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I’ve never been able to do the cube without help from a guide. 
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Thu Aug 12, 2010 9:57 am |
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Amnesia10
Legend
Joined: Fri Apr 24, 2009 2:02 am Posts: 29240 Location: Guantanamo Bay (thanks bobbdobbs)
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I have never been able to do a Rubiks cube without help from a screwdriver. 
_________________Do concentrate, 007... "You are gifted. Mine is bordering on seven seconds." https://www.dropbox.com/referrals/NTg5MzczNTkhttp://astore.amazon.co.uk/wwwx404couk-21
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Thu Aug 12, 2010 2:32 pm |
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bobbdobbs
I haven't seen my friends in so long
Joined: Thu Apr 23, 2009 7:10 pm Posts: 5490 Location: just behind you!
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3 step method remove one corner cube take apart cube put together finished 
_________________Finally joined Flickr
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Thu Aug 12, 2010 2:34 pm |
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paulzolo
What's a life?
Joined: Thu Apr 23, 2009 6:27 pm Posts: 12251
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That’s pretty much how I’ve done it in the past.
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Thu Aug 12, 2010 3:42 pm |
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Amnesia10
Legend
Joined: Fri Apr 24, 2009 2:02 am Posts: 29240 Location: Guantanamo Bay (thanks bobbdobbs)
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A slight variation on my solution but that works for me as well.
_________________Do concentrate, 007... "You are gifted. Mine is bordering on seven seconds." https://www.dropbox.com/referrals/NTg5MzczNTkhttp://astore.amazon.co.uk/wwwx404couk-21
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Thu Aug 12, 2010 4:09 pm |
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