## Most recent change of RubiksCube

Edit made on January 22, 2009 by derekcouzens at 15:53:52

Deleted text in red /
Inserted text in green

WW

HEADERS_END

A commercially made puzzle, invented by Hungarian Erno Rubik, consisting of a cube of independently rotating faces.

In the starting position each face has 9 stickers of the same colour.

The challenge is to return the cube from a random position to the starting position.

IMG:Rubikscube2.jpg IMG:arrow2.png IMG:rubikcube.jpg

There are 43,252,003,274,489,856,000 possible positions of the cube.

The current best algorithm for solution of the cube requires at most 22 moves,

and it can be proven by counting arguments that there exist positions needing

at least 18 moves to solve.

Such algorithms require great computer resources to execute whereas algorithms used by humans are much longer but far easier to learn and use.

| Video tutorial | http://uk.youtube.com/watch?v=LIKEvDRuLAg |

| Printable algorithm | http://peter.stillhq.com/jasmine/rubikscubesolution.html |

| Animated cube | http://vanderblonk.com/cube/cubeapplet.asp?type=Generator&alg=RR'F' |

| Animated cube | http://vanderblonk.com/cube/cubeapplet.asp?type=Generator&alg |

You can use the animated cube to test the algorithm.

There are championships for solving the Rubik's cube in the shortest time, using one hand and blindfold.

----

By thinking of each position as a permutation from the starting position, we

can think of the set of positions as a group. This group is generated by the

collection of "primitive moves".

This is a good example of how a single collection can be thought of in different

ways. The actual position is equivalent to the sequence of moves required to

get to it from the initial position. That means that a position is equivalent

to a permutation, or to a sequence of permutations, /etc./

The Rubik's Cube is therefore a good place to explore some fundamental group theory.

As a quick start, the theory of commutators (an element of the form EQN:aba^{-1}b^{-1}

is a commutator) gives an insight into constructing sequences that move a very

small number of the pieces. From that, entire solution algorithms can be devised.

----

http://en.wikipedia.org/wiki/Rubik_Cube

http://mathworld.wolfram.com/RubiksCube.html