rubic's cube (for the really bored)

Originally posted by BTBasham
I've mastered solving the rubiks cube in about 40 seconds to a minute 20. However, I'm still not sure what you're asking. From any point it is POSSIBLE to solve it in 23 moves.. and "correct" is relative. if i have it all solved, then rotate all the corners in threes, then none are "correct" relative to the stationary cubes. So, 0 and 23 are your answers if I understand the question.

What is your general strategy for solving it? I was quite good at the cube in junior high school...I could get through it in less than five minutes (granted that's nowhere near your time).

Personally, I made X's on opposite faces, filled in the middle edges, then solved the problems of "flipped" squares or squares on wrong parts of the cube. The other sides almost magically fell into place. This last part was always difficult for me and I never memorized move sequences. The real key for me was to hold the cube in one plane. Rotating it about and trying to move the pieces resulted in no end of headaches as I could never remember the original orientation if I made a mistake.

When you say it's "possible to solve it in 23 moves," do you mean that in any given situation? Because I recall that "flipping" a piece (meaning that the whole thing was solved except for two colors of the same square on the wrong faces) always took me at least 10 moves or so.

Originally posted by Poison Godmachine
What is your general strategy for solving it? I was quite good at the cube in junior high school...I could get through it in less than five minutes (granted that's nowhere near your time).

Personally, I made X's on opposite faces, filled in the middle edges, then solved the problems of "flipped" squares or squares on wrong parts of the cube ...[text shortened]... pt for two colors of the same square on the wrong faces) always took me at least 10 moves or so.

I've only done one once, from first principles, but it took more than an hour.
I've met someone who had memorized several algorithms, invented some of his own, and practised a great deal, who could solve a standard cube in around 20 seconds (he said it takes ~90 moves on average). He could also solve it in less than a minute one-handed while juggling three balls in the other hand. While the big deal was obviously the method, part of his speed was due to hand exercises he did and his practice of spraying WD-40 into the joints--''lubing the cube''. Most impressive 😲.

Originally posted by Poison Godmachine

When you say it's "possible to solve it in 23 moves," do you mean that in any given situation? Because I recall that "flipping" a piece (meaning that the whole thing was solved except for two colors of the same square on the wrong faces) always took me at least 10 moves or so.

"Flipping" a single piece is impossible - in fact the number of flipped edges will always be even.

I don't know where 23 comes from - though I've heard that number more than once. It is often refered to as the length of "God's algorithm".

It is possible to establish a lower bound for the number of moves required to solve the cube from any position in the following way:

The 3x3x3 Rubik's cube has 4.3 x 10^19 configurations (see another thread for how to derive this number)

If we start with a solved cube, then after the first move there will be a further 18 arrangements (6 faces x 3 possible rotations)
After 2 moves there will be a further 18 x 15 arrangements ( 3 rotations x 5 faces - 'cos you wouldn't rotate the same face twice in a row)
After 3 moves there will be 18 x 15 x 15 more, etc.

Keep doing this and keep a running total and after 17 moves the number will exceed 4.3 x 10^19. Thus it will take at least 17 moves to generate all possible arrangements of the cube. Of course it could take more...... Perhaps someone came up with some more sophisticated reasoning and arrived at 23.

Originally posted by royalchicken
I've only done one once, from first principles, but it took more than an hour.
I've met someone who had memorized several algorithms, invented some of his own, and practised a great deal, who could solve a standard cube in around 20 seconds (he said it takes ~90 moves on average). He could also solve it in less than a minute one-handed while juggl ...[text shortened]... nd his practice of spraying WD-40 into the joints--''lubing the cube''. Most impressive 😲.

No one like an overachiever. 🙄

Originally posted by howardbradley
"Flipping" a single piece is impossible - in fact the number of flipped edges will always be even.

On innumerable occassions, I have had the cube completely solved, but adjacent edges would have the colors reversed on the middle square (if red was on top and green was to the right, the top right middle piece would have green on top and red on the right). I was always able to "flip" that particular square, but it was quite painstaking, and I had to make sure that I didn't rotate the cube from its original orientation..

So I dug out my cube and once again, I encountered ONE flipped piece as described in my earlier post. However, the only way I was able to solve the problem was to move the slices so that I ended up with two or four pieces flipped. So I was half right, I guess, in my post above. It's been a long time since I messed around with this cursed thing.

The quickest way I was able to solve the flipped pieces problem was this: the ' symbol denotes a counter-clockwise move, R= right slice, T = top slice, -> and <- denote moving the middle slice in the indicated direction. Make sure to hold the cube so that one of the flipped pieces is on the right slice (though there are some exceptions).

R'
<- twice
R twice
-> twice
R'
U twice
R
-> twice
R twice
->
R
T twice
<-

That's twelve moves, though I realize that flipped pieces don't occur from every starting configuration. But does anyone know a quicker way when presented with this heinous problem? I was screwing around with this all day. If there's a quicker method, I certainly can't figure it out.