# Thread: Rubik's cube can be solved in 20 moves or less!

1. ## Rubik's cube can be solved in 20 moves or less!

AFP: Study uncovers every possible Rubik&#39;s Cube solution

WASHINGTON — An international team of researchers using computer time lent to them by Google has found every way the popular Rubik's Cube puzzle can be solved, and showed it can always be solved in 20 moves or less.

The study is just the latest attempt by Rubik's enthusiasts to figure out the secrets of the cube, which has proven to be altogether far more complicated that its jaunty colors might suggest.

At the crux of the quest has been a bid to determine the lowest number of moves required to get the cube from any given muddled configuration to the color-aligned solution.

"Every solver of the Cube uses an algorithm, which is a sequence of steps for solving the Cube," said the team of mathematicians, who include Morley Davidson of Ohio's Kent State University, Google engineer John Dethridge, German math teacher Herbert Kociemba and Tomas Rokicki, a California programmer.

"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."

The research, published online, ends a 30-year search for the most efficient way to correctly align the 26 colored cubes that make up Erno Rubrik's 1974 invention.

"It took fifteen years after the introduction of the Cube to find the first position that provably requires 20 moves to solve," the team said. "It is appropriate that fifteen years after that, we prove that twenty moves suffice for all position."

Using computers lent to them by Google -- the company won't disclose how many or how powerful they are -- the team crunched through billions of Cube positions, solving each one over a period of "just a few weeks."

The study builds on the work of a veritable pantheon of Rubik's researchers, starting with Morwen Thistlethwaite who in 1981 showed 52 moves were sufficient to reach the solution from any given Cube position.

By May 1992, Michael Reid showed 39 moves was always sufficient, only to be undercut a mere day later by Dik Winter, who showed 37 moves would work.

Rubik's enthusiasm extends not only to God's number, but the speed with which the tricky puzzle can be solved.

The current world record holder is Dutch Erik Akkersdijk who successfully solved the puzzle in just 7.08 seconds.

More details here.

2. Sing it for me babeh...

"Everything old is new again....l

Rubik's Cube can be solved in two \$oves, from my experience.

Pull it apart.

Put it back together.

3. Originally Posted by Burgey
Sing it for me babeh...

"Everything old is new again....l

Rubik's Cube can be solved in two \$oves, from my experience.

Pull it apart.

Put it back together.
Haha, yes. That's how we all get started, isn't it. Anyway, there's a lot to learn about it even if you solve it by that method. The thing is an architectural marvel. BTW, did you know that if you don't put the pieces back in the solved configuration after dismanting it, there's only a 1 in 12 chance that you will be able to solve it from that position?

4. 6 moves IMO

5. Originally Posted by andyc
6 moves IMO

Brilliant.

Its such a long long time ago when I first got my Rubik's cube from a trip to Europe. After that you couldn't get the damn thing off my hands. I was at it on the dining table and in the loo :-)

Then one night, long after my wife had gone off to sleep, I finally got it all. It must have been around 3.00 am in the morning. I shook her up and told her I had done it. She mumbled "great" and turned over to go back to sleep. I kept the cube high up on my bookshelves so that I could show it to my young kids next morning.

Next day I got up late and had completely forgotten about it when at breakdfast the missus said, "You know I had a strange dream last night about you having finally solved that damn cube puzzle of yours."

I jumped up and screamed "I did do it. It wasn't a dream"

Unfortunately, the kids had already left for school and there was no way to contact them and give them the news. They had to wait for 24 hours before they could boast about it to their friends :-)

Later I got to master it better and could do it in a matter of minutes (never seconds) but it was always a big draw. I would go to a friends house and he would introduce me as "Meet my friend, the only guy I know who can do the Rubik'z cube" and some one would get hold of one and I would be made to act like the little kids who are asked by their parents to song the national anthem for the benefit of their guests

It was a real pain.after the novelty wore off :-)

6. I have real respect for people (like my Dad) who figured out the algorithms on their own after months of effort and patience. I actually went and looked up the ready-made algorithms for the layer-by-layer approach and it was all too easy once you do them once or twice.