About Rubik cube problems

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wij

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Aug 5, 2022, 6:02:36 PMAug 5
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Is there any program that solves scrambled Rubik cube in 20 moves?
From what I searched on the internet, the answer is probably NO.
Then, from the example https://rubiks-cube-solver.com/solution.php?cube=0111111113222222222334333334144444644555555555663666666
the Rubik cube remaining only 2 mismatched corners may still need 17 moves
to finish, this suggests to me all other strategies commonly seen on the
internet (e.g. layer by layer, cross centers first,...) are not much different
from any chosen random cubes that are ~3 steps closer to the goal.
Is my understanding of the Rubik cube problem right?

Andy Walker

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Aug 6, 2022, 7:57:45 AMAug 6
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On 05/08/2022 23:02, wij wrote:
> Is there any program that solves scrambled Rubik cube in 20 moves?

The reference I gave a few days ago, "http://www.cube20.org",
has a link to their source. I don't know whether this is what you
want.

> From what I searched on the internet, the answer is probably NO.
> Then, from the example https://rubiks-cube-solver.com/solution.php?cube=0111111113222222222334333334144444644555555555663666666
> the Rubik cube remaining only 2 mismatched corners may still need 17 moves
> to finish, this suggests to me all other strategies commonly seen on the
> internet (e.g. layer by layer, cross centers first,...) are not much different
> from any chosen random cubes that are ~3 steps closer to the goal.
> Is my understanding of the Rubik cube problem right?

Probably not. Solving layer by layer, etc., is certainly far
from optimal, witness the much larger upper bounds given by the early
solvers [such as Singmaster, Conway, Thistlethwaite]. Note that ~98%
of all positions are >= 17 moves from solution; it wouldn't be at all
surprising if some of them are visually quite nearly solved. In the
days when I was interested in this sort of problem in relation to
sliding-block puzzles [see

http://www.cuboid.me.uk/anw/Research/CMate

(includes source, of a sort); very old] and chess endgame databases,
there were always "surprises" where problems turned out to have very
long or very short solutions.

--
Andy Walker, Nottingham.
Andy's music pages: www.cuboid.me.uk/andy/Music
Composer of the day: www.cuboid.me.uk/andy/Music/Composers/Hertel
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