How many moves in a rubiks cube

For a long time, it was uncertain whether the upper bound could be any lower. On the other hand, the hunt was on for lower bounds of the number of moves necessary. It was well known that certain cube configurations required eighteen moves, but it was unclear whether the number could be higher. Were there configurations even more difficult to solve?

In the mid 90s, a special configuration, the superflip , was found, that actually required twenty moves. This was the new lower bound, and it would take another fifteen years before the upper bound was found. In the answer was found: Twenty was also the upper bound!

This means that twenty moves is both necessary and sufficient in order to solve any configuration of Rubik's cube. It is necessary due to configurations like superflip, and it sufficient because you never need more than twenty moves to solve any cube.

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Andy Kiersz. The Rubik's Cube is an iconic puzzle toy. But it is mathematically complicated — there are 43 quintillion possible configurations of the Cube. Over 30 years after the Cube was invented, a group of mathematicians showed, using a bank of supercomputers at Google, that any cube could be solved in at most 20 moves. Get a daily selection of our top stories based on your reading preferences. While one could spend a lifetime checking each configuration to see if it leads to the solution, there are a whole host of solutions published on the web.

But, what is the fastest way to solve a Rubik's cube? In , 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. However, he said, the team may not be done with the Rubik's Cube just yet.

They might now turn their attention to the four-layered version or could attack other mathematical problems related to the classic cube. The work was carried out with John Dethridge, an engineer at Google, Herbert Kociemba, a maths teacher and Tomas Rokicki, a programmer from California.

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