- Sep 1, 2003On Mon, Sep 01, 2003 at 11:48:01AM -0000, jasmine_ellen wrote:
> I remembered that DanK had something like this on his site about a

I'll describe the beginner and intermediate methods that I once used.

> beginner method, an intermediate method and an advanced method. This

> is actually what I was after. Who else has something like this on

> their site?

They are simplications of the Fridrich last layer system. You need to

first understand how that system works:

http://www.ws.binghamton.edu/fridrich/system.html#last

This general strategy, orienting first, then permuting, is good because

it is very easy to recognise the positions quickly. But instead of

orienting all the pieces at once, you just orient the edges first, and

the corners second.

BEGINNER METHOD

First, orient the 4 edges (ie. make a cross). There are only 4 patterns,

and one algorithm to solve them all! To view this, you need to use a

fixed width font:

--- --- -x- -x-

-x- xxx xx- xxx

--- --- --- -x-

For each pattern, apply the algorithm "R'U'F'U F R" and it will take you

to the next pattern. Eventually you will end up with a cross.

Improvement: notice that if you apply the algorithm when you already

have the cross, you will end up with a line. That means that you can

jump immediately from the 2nd pattern to the 4th pattern by applying the

algorithm backwards! So, this step should take an average of 6 moves.

Next, orient the corners. There are only 6 patterns apart from solved.

Look through this complete list, and find all the patterns (and

algorithms) that have a cross already formed:

http://www.ws.binghamton.edu/fridrich/Mike/orient.html

For the case when 3 corners need to be twisted, I recommend the Sune TM

algorithm from Petrus. See the applet at the top/right of his page:

http://lar5.com/cube/fas6.html

I think it's useful to learn to twist them forwards and backwards:

- R U R'U R U2 R'

- R'U'R U'R'U2 R

To see that done fast, have a look at the quicktime movies at the bottom

of this page:

http://lar5.com/cube/speed.html

I recommend this algorithm because one of the other orientation cases

can be solved by just applying this algorithm twice. To know which case

I'm talking about, apply this to a solved cube: RU2R'U'RUR'U'RU'R'.

Now, apply the sune (RUR'URU2R') twice:

RUR'URU2R' + RUR'URU2R'

Notice that the moves in the middle cancel out? So you can actually do:

RUR'URU'R'URU2R'

which is an "optimal" solution.

Next, permute the corners (yes, before the edges). Most of the time

there will be a 3 cycle of corners. In this case, look at the 4 sides of

the last layer. On one of the sides, the two last layer corners will be

matching in colour. Hold those two corners on the back side and do:

R'FR' B2 RF'R' B2 R2

Now the corners should be solved. If you don't find any two corners that

match, apply the above algorithm and that should result in a position

where two corners match. Don't worry, this case rarely happens. If you

want, you can learn a special algorithm for that case by picking the

most attractive one from:

http://www.ws.binghamton.edu/fridrich/Mike/permute.html

The "Y" pattern on that page has the desired corner effect.

Next, permute the edges. Again, most of the time, there will be a 3

cycle of edges. You need to learn to cycle the edges forwards and

backwards:

- R2U FB'R2F'BU R2

- R2U'FB'R2F'BU'R2

Sometimes, all 4 edges need to be swapped in opposite pairs. That's an

easy case, so why not learn it:

RLU2R'L' [U] R'L'U2RL

The [U] means rotate the whole cube from the up side, 90 degrees.

There's also a rare case where all 4 edges need to be swapped in

adjacent pairs. The algorithm's difficult so it's not worth learning.

INTERMEDIATE METHOD

First, orient everything like the beginner method. Then permute

everything like the full blown Fridrich method.

How can you learn all the permutations? See my previous email:

http://groups.yahoo.com/group/speedsolvingrubikscube/message/4736

There, I list which algorithms to learn first, and which algorithms to

learn last.

ADVANCED METHOD

You already know enough! It is not necessary to learn 40 orientation

algorithms. 6 is enough. Gilles Roux proved that it is possible to

achieve sub-20 times with just these 6 orientation algorithms and 13

permutation algorithms. He used the petrus method for the first two

layers which gives you a cross automatically when you get to the last

layer. Using that strategy, those extra orientation algorithms are not

needed.

Ryan - << Previous post in topic Next post in topic >>