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myaccount80 | 3 years ago

It’s called Devil’s algorithm but I believe it is not know yet whether it exists or not

https://getgocube.com/play/devils-number/

discuss

order

hvdijk|3 years ago

It has to exist: it's a mindbogglingly large but finite number of possible permutations, and to go from any one permutation to any other takes a finite number of moves. Therefore, if you can enumerate all possible permutations in some way, any arbitrary way will do, you have a Devil's algorithm by going through them in that order. The question is not whether a Devil's algorithm exists but what the shortest one is.

owalt|3 years ago

Worth noting that the Devil's algorithm is not a sequence of turns you repeat over and over, but one that takes you through every possible cube state. You "abort" it partway through when you reach your desired state.

988747|3 years ago

Somewhat related: I was playing with cube recently, and, starting with solved state, I started doing sequence of two moves that came to my mind: rotate right side down, then the bottom, clockwise. After maybe a 100-150 repetitions (I did not count, just did the moves mindlessly for couple minutes) I went back to solved state. I wonder if there are more such sequences, and how long it takes to go back to original state. The obvious difference from Devil's algorithm was that the 2x2 sub-cube remained untouched the whole time, only the edges were messed up.

lupire|3 years ago

Every sequence behaves this way (For all sequences S, there exists n_S such that S ^ n_S equals S^0, the starting state.) Proving this is an introductory problem in Rubik's theory. Try it!

zeroonetwothree|3 years ago

Because there are only finitely many states, repeating one move will inevitably get you back to where you started from.

Also check out Lagrange’s theorem in group theory