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Le 17/09/2015 17:53, scott a écrit :
>>> Take a standard Rubik's cube and rotate one face 90 degrees.
>>> Then rotate an adjacent face 90 degrees in the same direction.
>>> How many times do you have to repeat those two moves
>>> (repeatedly on the same two faces) before the cube gets back to
>>> the same state it started in?
>>> 
>> There is a Rubik's cube in the IRTC (as source). It can be 
>> programmed/shuffled with a string of text... so goes on topic and
>> render a few frames with the string generated according to the
>> frame number.
> 
> Interesting ... I needn't have written the SDL code to draw my own
> one then :-) Still I'm interested in why the answer is so high for
> an apparently simple system, but I'm having a hard time trying to
> visualise in simpler terms what is going on.
> 

It was only recently, IIRC, that it was proven that the deepest
distance from any 2 positions was at most 19 moves. (that includes the
hell-mixed position and the "all-faces-of-uniform-colour" position).

Then there is the problem: a path of 19 moves, but which ones, and in
which order.
A totally different issue.

I always solved my Rubik's with internet / programs.

The forest might only have a depth of 19, but you can circle around a
long time between the trees.
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