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Date: Mon, 09 Nov 1998 15:37:18 -0800
From: Derek Bosch
To: Han Wen
Cc: cube-lovers@ai.mit.edu
Subject: Re: Query for Corners-First Method Rubik Solution
References: <19981104032938.14284.rocketmail@send102.yahoomail.com>
Here's the method I use to solve Rubik's Cube in 30 seconds or less.
My notation is as follows:
F = turn front face clockwise 90 degrees.
F' = turn front face counter-clockwise 90 degrees.
F" = turn front face 180 degrees.
U = turn top face clockwise 90 degrees.
R = turn right face " " "
L = turn left face " " "
B = turn back face " " "
D = turn bottom face " " "
^ = move middle slice 90 degrees up.
v = move middle slice 90 degrees down.
OK. Now the order I do things is corners, edges on two OPPOSITE sides (Right
and Left), followed by the middle slice edges.
(1) Corners:
I solve my corners a bit wierdly, but I find it is really fast. I position
any four corners of the same color on a side. I don't care what colors are
on the adjoining faces right now, as I fix them later.
(1a)
Once I have the 4 corners of the same color, I turn the cube so that those
colors are on the down face. Now there are a few combinations that can occur
on the top face:
All corners on top face same color: Goto (1b)
Three corners need to rotate clockwise (position like below o=no rotate)
(+ = needs clockwise rotation)
(- = needs counter-clkwise rot.)
+ + Move: R'U"RUR'UR and goto (1b)
+ o
Three corners need counter-clockwise rotate:
- o Move: RU"R'U'RU'R' and goto (1b)
- -
One corner needs clockwise rotate, One needs counter-clockwise rotate:
3 cases:
+ - Move: RU"RU"RUR" and goto (1b)
o o
- + Move: RUR'U'F'U'F and goto (1b)
o o
o - Move: R'URUBU'B' and goto (1b)
+ o
Two corners need clockwise rotate, Two need counter clockwise:
2 cases:
+ - Move R"U"RU"R" and goto (1b)
- +
- + Move RUR"F'R"UR' and goto (1b)
- +
(1b)
Now, you should have two opposite sides, with the corners of those
two sides the proper color.
We have to correct the 4 remaining sides to get corners in the right
place, before we can move onto edges. To do this, count the number
of sides that have the upper pair of corners the same color. Also
counter the number of sides that have the lower pair of corners the
same color.
All four sides (upper and lower) corner pairs match. Goto (2)
No sides' corner pairs match. Do Move R"F"R". Goto (2)
One Bottom corner pair matches.
Move that corner pair to the Down-Left position.
Move R"UR"U'R"UR"U'R. Goto (2)
One Top corner pair matches. Turn Cube over, and do previous moves.
One Top and one Bottom pair matches.
Move both corner pairs to the front face.
Move R"UR"U"F"UF". Goto (2)
All Bottom pairs match.
Move R"UR"U"F"UF"U"L"UL". Goto (2)
All Top pairs match. Turn Cube over, and do previous move.
All Bottom pairs match. One Top pair match.
Move Top Pair to Left-Upper position.
Move R"UR"U'R"F"U'F"UF". Goto(2)
All Top pairs match. One Bottom pair match. Turn Cube over, and do prev.
(2) Solving two Opposite Sides.
Now, all the corners should be solved. You should move the center of
each cube to its respective corners, to get an X on each side (at least
on two opposite sides). From now on orient the cube so that the two
opposite sides are right and left.
(2a)
Solve three edges on the left face with the following moves.
U'^U - moves the edge piece in the Front-Down position to the Up-Left
position.
UvU' - moves the edge piece in the Back-Down position to the Up-Left
position.
This is easier done with a cube in your hand, and try and see how this
works. This will mess up the centers and edges in the middle slice, as well
as the Up-Right edge. Don't worry about this. As long as you keep this
orientation, and rotate the left face to get ready for a new edge to be moved
you can solve three out of four of the edges on the left face.
(2b)
Solve four edges on the right face:
First, rotate the left face, so that the unsolved edge is in the Up-Left
position.
Then, using the following moves, solve all four edges (similarly to step 2a).
U^U' - moves the edge piece in the Front-Down position to the Up-Right
position.
U'vU - moves the edge piece in the Back-Down position to the Up-Right
position.
(2c)
Solve remaining edge on left face:
2 cases (other than already solved):
edge in place, needs to be flipped: Use U'vUvUvU'
otherwise, move edge to Down-Front position, using v or ^.
if the front color (of the DF edge) is the same as the left face color,
Use U'vU"vU'
else Use vU^U"^U
(3)
Solve middle slice edges.
First use ^ or v to position middle slice centers in proper faces.
(3a) Position edges:
3 cases (other than all in place):
only three edges out of place:
position cube such that DF needs to go to UB and UB needs to go to UF.
Use ^U"vU".
all four edges need to move:
if UF needs to go to DB, Use ^F"B"vF"B".
otherwise, position so that UF needs to go to UB, Use U'^^U'^^.
(3b) Flip required edges:
3 cases (other than no flips needed).
all four need flipping, use FR'F'^U^U^U^UFRF'
two edges need flipping, both on same face. Turn cube so that these
edges are the UF and UB edges. use ^U^U^U"vUvUvU"
otherwise, turn cube so UB and DF need flipping, use F"^U^U^U"vUvUvU"F"
That should do it. I apologize for the roughness of this solution. I think
diagrams would help it a lot. If you have any criticism or ideas that could
help this solution become more readable, let me know.
Note, this solution is very close to Jeff Verasano (sp) and
Minh Thai's methods...
D
--
Derek Bosch "A little nonsense now and then
(650) 933-2115 is relished by the wisest men"... W.Wonka
bosch@sgi.com