Rubik's Cube solutions
Laboratory
Rubik's Cube solution: Lars Petrus method
The Lars Petrus resolution method is useful to quickly resolve
the Rubik's Cube.
Using this method Lars Petrus won the Swedish championship and
arrived fourth in the world championship of Budapest in 1982.
Lars says that in a good solution to resolve the Cube you have
to do something useful in every move, but in a layer by layer
method you have to unmake the Cube many times. The number of moves
can decrease from 100 to 60.
In this first step we have to build a 2x2x2 cube positioning a corner
and the three near edges in the right place and the right orientation.
To do this we choose a corner we want to position and we find the three
corresponding edges: for example, choosing the corner with colors A, B
and C, we find the three edges with colors A and B, A and C, B and C.
An algorithm that will ever work is this:
- place side by side one of the three edges to the corner orienting it so that the same colors are on the same face (edge well oriented) anywhere on the Cube. Is not important if they aren't in the correct position;
- place one of the other two edges in its correct position and right orientation regarding the Cube (the A and B colors edge will be between the central cubes A and B, so that the colors will be in the corresponding faces);
- join the first two pieces to the third, placing them in the correct positions regarding the Cube (they should already be well oriented);
- now we position correctly the third edge, in the right orientation.
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If you want to increase the speed in completing thi step you have to choose, at the starting, the corner more easy to solve from the eight you have. Normally in a match you have from 15 to 30 seconds to see the Cube before starting; to choose the easier corner should be sufficient from 2 to 5 seconds.
To save other moves and so to be quicker is needed to imagine the movements of all four piaces during the composition of the 2x2x2 cube. You can save 5 or more moves.
Other explanations on how to find the easier edges and on how to save moves will be gave in an other time.
