Rubik's Cube
This puzzle is now well over 25
years old yet still seems to keep going. This is very much a classical
section-at-a-time solution and will, unfortunately, not garner you the world
record, for that you need to look for other more integrated solutions but, at
least, this gets you a cube looking like the one you bought. This was actually
set as a week's tutorial work during my Eng Sci course - sadly I don't have the
notes but here we go.
Firstly, complete one face; I'm
not going to tell you how. I'm going to use GREEN in this example. Really if you
can't do that you aren't ready for this. Now I'll walk you through the stages
but first let's clarify some nomenclature. Your cube has 6 faces (if it doesn't
it's not a cube). I shall call them:
Upper (U), Down (D), Left (L),
Right (R), Back (B) and Front (F)
and I shall define a move as 90
degree clockwise rotation as if you were looking at that face square on. So the
instruction F means rotate the Front face 90 degrees clockwise. B' means rotate
the Back face 90 degrees anti-clockwise. Have a think about that for a moment.
As you look at the cube, that means both F and B face would rotate together,
from your current perspective. Finally R2 means rotate the Right face
through 90 degrees twice (no, it doesn't matter which way!).
The little diagrams will show the
uppermost face and pertinent edge colours only. So always look for the
core 9 squares on the upper face.
Having sorted the upper layer, get
the centre squares of the middle layer in place under their respective top edge
- again no help here.
The middle layer
OK, now let's see how to sort
those middle layer edges. Find the missing edge - say YELLOW/ORANGE - and rotate
this until it is underneath its matching colour centre square on the middle
layer, like this:
Keep that face towards you, check
to see if the secondary colour is on the left or right face. If it's on the left
face, execute this move:
DLD'L'D'F'DF
Visualising this move: take the target piece away from its future location,
bring that location down, bring the piece back, return the location, back again
and finally pick up the corner.
If it's on the right face (as
above):
D'R'DRDFD'F'
as before but the other way round.
Complete the middle layer. If you
find that an edge is in the correct place but back to front, just move it to the
bottom layer, replacing it with anything and repeat the above.
The bottom cross
Now we need to sort the cross on the bottom, so turn the cube upside down. GREEN is now down. We will work now
with green on the bottom. The top - blue for me - can look like this:
1. A reversed L
In which case execute this:
FURU'R'F'
start with the F, then sort of V shape so U first then R then undo.
2. or a horizontal line
In which case execute this:
FRUR'U'F
I is a Regular shape so after F, an R then U then undo.
3. or merely a centre dot
In which case execute the actions
in step 1 and review, then do what's needed!
The bottom (now top) corners
Now we need to sort the corners,
so first places as many corners as you can in the correct place. It is unlikely
to be all 4 but hopefully will be 2 on one edge. If it's 2 diagonally, you need
to use this action twice. With the green face down, yellow facing you, white
away from you, purple left and orange right, we see the correct corners (wrongly
oriented) on the left:
Now execute:
LU'R'UL'U'RU2
a one-off technique - note the alternating L/R sequence L R' (so you rotate both
sides towards you) L' R (then away again), with
interleaved U' U U' U and a final U to get it straight.
Clearly you may need this twice!
Orienting the corners
OK, this is officially the
nightmare section, there are so many variations but fortunately only 2 actions.
But is is critical that you place you cube correctly before each action and
choose the correct action. There are actually 7 variations that look like this:
1. The anti-clockwise position.
One corner is correct and the other 3 need (if you look at them point on,
colours as above) an anticlockwise rotation to be correct. Note the top left
corner is correct. Hold the cube (with green down) like this:
and execute:
R'U'RU'R'U2RU2
Anti-clockwise so a ' first and all Us are '. Just learn that the good corner is
top left, then its all Rs so R' (AC) U' then reverse the R, U', reverse the R'
then U' twice, etc.
2. The clockwise position. One
corner is correct and the other 3 need (if you look at them point on) a
clockwise rotation to be correct. Note here the bottom left corner is correct.
Hold the cube (with green down) like this:
and execute:
RUR'URU2R'U2
opposite of above, learn that the good corner is bottom left, then it starts
clockwise. R then U, reverse the R', then U, reverse the R then U twice, etc.
3. 2 corners correct and 2 on the
same face incorrect (they may not be white). Hold the cube like this:
and execute step 1. Review the
position and execute step 2.
4. 2 corners correct and 2 on the
opposite faces incorrect. Hold the cube this this:
and execute step 1. Review the
position and execute step 2.
5. 2 diagonal corners incorrect.
Hold the cube like this:
and execute step 2. Review the
position and execute step 1.
6. A combination of step 3 and 4.
Hold the cube like this:
and execute step 1. Review the
position and execute step 1.
7. Finally, a double step 3. Hold
the cube like this:
and execute step 1. Review the
position and execute step 1.
Sorting the cross.
We're nearly there. The cross on
the (blue) side can be correct or in one of 4 states:
1. 3 edges require a clockwise
translation. Hold the cube like this:
and execute:
R2UFB'R2F'BUR2
clockwise to clockwise moves. R twice, U then both F and B the same way when
viewed from the front, R twice undo F and B, U, tidy up.
2. 3 edges require an
anticlockwise translation. Hold the cube like this:
and execute:
R2U'FB'R2F'BU'R2
anti-clockwise so all ' moves. R twice, U' then as above.
3. An opposite sides swap. Hold
the cube like this:
and execute one of the above steps
then review and repeat.
4. A diagonal sides swap.
Hold the cube like this:
and execute one of the above steps
then review and repeat.
Now you're done!
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Last updated:
Saturday, 17 February 2007 19:38