Rubiks Cube

In 1997, Richard Korf, a professor of computer science at UCLA, said that his research showed that a Rubik's cube could be solved in a median of 18 moves, and no more than 20 should be needed. However, he was not able to prove this. The lowest provable number of moves needed to solve a Rubik's cube was 27—until now. A pair of computer science researchers from Northwestern has developed a proof showing that a Rubik's cube in any configuration can be solved in 26 moves. While that is not much of an improvement, it is still mind-boggling; imagine needing only 26 moves to get from a state as unique as 1 in 43 quintillion to the solution of the puzzle.

Rubiks Cube Science