Unsolving the Rubik’s Cube


This blog post has moved to https://matthewvaneerde.wordpress.com/2008/05/16/unsolving-the-rubiks-cube/

Comments (10)

  1. Ron says:

    Hi Matthew,

    Interesting post.

    A few years ago my friend Katsuyuki Konishi asked the same question.

    This is what we came up with:

    http://www.planet-puzzle.com/cubekyukan3x3.html

    Have fun,

    Ron

  2. Anon says:

    Great Thanks I was thinking about this also the other day.

  3. diesel says:

    isn’t the fact that no squares adjacent are the same color actually ordered?  a truly random distribution would of course contain sqaures next to each other that are the same color.  You’re aren’t making the cube disordered, only ordered on the opposite end of the idea of colored faces.

  4. Exactly – this is the Rubik equivalent of forced busing.

  5. Torry says:

    Can someone writ out all the moves together in-line?

    I did all edge switching just fine, but after I did the corner swapping I still had color next to each other.  I must have gotten confused trying to convert the instructions to apply to my cube.

    "Reposition all eight corner pieces to the opposite corner

    The following move repositions FLT to TLH, TLH to TRH, and TRH to FLT:

       L-1 T R T-1

       L T R-1 T-1

    As a convenience, the following mirror-image move repositions FRT to TRH, TRH to TLH, and TLH to FRT:

       R T-1 L-1 T

       R-1 T-1 L T

    Strictly speaking, you can get away with only memorizing one of these moves – each move is equivalent to holding the cube in a different position and executing the other move twice.

    Pick three faces that share a common corner – say, the faces whose center cubes are red, white, and blue.  Position the cube so it is balancing on that corner.  Note that the corner cubelets now occupy four distinct strata:

      1. The "top" corner.

      2. The three corners that share a common edge with the "top" corner.

      3. The three corners that share a common edge with the "bottom" corner.

      4. The "bottom" corner.

    This part of unsolving the cube is completed in four distinct phases:

      1. Unsolve the "top" corner – that is, find the red/white/blue cubelet (it’s on the bottom corner) and move it to the top.  This will require two moves, which will to a certain degree randomize the positions of all of the rest of the corners.

      2. Unsolve the three corners that share a common edge with the "top" corner, without disturbing the cubelet in the "top" corner, or any already-unsolved cubelets in this stratum.

      3. Unsolve one of the three corners that share a common edge with the "bottom" corner, without disturbing any of the cubelets in the two strata above.

      4. Finally, there are three remaining un-unsolved cubelets.  Unsolve all three of these simultaneously – this will take precisely one execution of one of the two moves above."

  6. Dustin says:

    i found two reds touching

  7. Hmm… you're right.  Is there a way to save this?

  8. OK, I think I found the problem.  Updated post.  (One of the red tiles should have been orange.)

  9. stef says:

    Hi Matthew, that's what i was looking for. Thank you!

    For the case, that so. wants to use the common notation (red center is up, yellow front, blue right), here is it:

    U2 F2 D2 B2 U2 R F2 D2 L2 D2 L U B F2 R' F' D' L' F2 U2 B U'

  10. stef says:

    … even shorter:

    F2 U R' U2 L B' L2 U B D' L B' F' U F2 U R' D'

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