Date: Fri, 18 Aug 89 14:17 EDT
From: Allan C. Wechsler <ACW@YUKON.SCRC.Symbolics.COM>
Subject: the 3x3
To: rp@xn.ll.mit.edu, cube-lovers@ai.ai.mit.edu
In-Reply-To: <8908181621.AA18188@XN.LL.MIT.EDU>
Message-ID: <19890818181707.3.ACW@WHIMBREL.SCRC.Symbolics.COM>

    Date: Fri, 18 Aug 89 12:21:29 EDT
    From: Richard Pavelle <rp@xn.ll.mit.edu>

    I took some time off this week and began playing with the cube to
    teach one of my kids how to solve it. I had not tried for perhaps 5
    years. To my surprise I had forgotten a few transformations while
    recalling a few which are "equally difficult". It took about 10 hours
    to get back to the stage where I can solve it in about 3 minutes
    except for the flip of two opposite edges. I recall that we discussed,
    in this forum, a nice procedure for this move many years ago and I
    wonder whether anyone recalls it.

Recall the "Extended Befuddler" language:

B, F, U, D, L, R are counter-clockwise quarter twists.
Lower-case are clockwise.

I, i, J, j, K, k are whole-cule rotations agreeing in sense and axis
with B, F, U, D, L, R, in that order.

We group together sequences that are order-independent.  These sequences
almost always correspond to intuitive "moves".

And now, to flip the FD and BU edges:

;;; First monoflip:
f	; Get FD edge into equator.
jUd	; Slice it to the back.
FF	; Turn the vacated slot over
JuDJuD	; and slice the cubie back into the inverted slot.
F	; Move the cubie to the top.
;;; Segue
UU	; Exchange it with the other edge to be flipped.
;;; Second monoflip:
f	; Move the new edge into the equator,
JuDJuD	; slice it to the back the long way,
FF	; turn the vacated slot over,
JuD	; and slice the cubie back into the inverted slot, the short way.
f	; Get it back to the top
;;; Coda
UU	; Un-segue 
FF	; and take first edge back to the bottom.
;;; Checksum of whole-cube moves: jJJJJJ = 1.
;;; 26 qtw, 13 "moves" including half-twists and slices.

I doubt if this is minimal, but it is so intuitive that I was able to
type this sequence without a cube in my hands.

    Also, to what extent have others shared my experience of forgetting
    moves?

Some.