Abstract

We give an expository account of our computational proof that every position of Rubik's Cube can be solved in 20 moves or less, where a move is defined as any twist of any face. The roughly $4.3 \times 10^{19}$ positions are partitioned into about two billion cosets of a specially chosen subgroup, and the count of cosets required to be treated is reduced by considering symmetry. The reduced space is searched with a program capable of solving one billion positions per second, using about one billion seconds of CPU time donated by Google. As a byproduct of determining that the diameter is 20, we also find the exact count of cube positions at distance 15.

Keywords

  1. group theory
  2. algorithm performance
  3. Rubik's Cube

MSC codes

  1. 20-04
  2. 05C12
  3. 20B40

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Information & Authors

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Published In

cover image SIAM Journal on Discrete Mathematics
SIAM Journal on Discrete Mathematics
Pages: 1082 - 1105
ISSN (online): 1095-7146

History

Submitted: 24 February 2012
Accepted: 19 February 2013
Published online: 19 June 2013

Keywords

  1. group theory
  2. algorithm performance
  3. Rubik's Cube

MSC codes

  1. 20-04
  2. 05C12
  3. 20B40

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