Monday, June 30, 2008

I solved the Rubik Cube!!

I finally am able to solve a scrambled Rubik Cube! I started playing with the cube when I was a kid in 1980s. I declared it as impossible to solve back then, and remain impossible after I have all grown up.

What makes it so difficult is that it is hard to build on your previous success. It is already hard to solve 1 side. If you can solve one side, you MUST mess it up to attempt to solve further. This frustrating cube seemed to have lost its popularity for a couple decades and now making a comeback. I knew there are solutions, I actually saw a booklet when I was a kid (which didn't come with my cube in 1980s), but the instructions were too hard for me.

It is decades later and now I am ready to tackle it again! Being able to solve it seems to be a fun skill to have. My new Rubik Cube comes with a 7-step solution sheet! But just following the instructions isn't so easy! Some sequence are hard to remember, and it is already the easiest layer-by-layer solution.

Terminology: each face of the cube is named: Up, Down, Left, Right, Front, Back, much like x-y-z axes. "U" means turn the upper face clockwise, "Ui" means turn it counterclockwise. Ok, so far so good.

My heart sank as I read the first step: you must solve the green cross on your own.

Fortunately after actually playing with the cube, it isn't so difficult to get the green cross. Then we can use a sequence to insert the green corners! Wow, without this it is hard to solve even 1 side.

Now, we can turn the solved green side to the bottom, the next step is the middle layer. If you see an inverted "T", you can move the tip of the inverted T left or right using a (fairly long) sequence.

Solving two layers are not too difficult.

Then it remains to solve the (blue) top. Now it gets harder.

You need to first get a blue cross. Look around for a specific pattern then apply another sequence to make the blue cross. It is not so hard yet.

The next step is to put the blue cross correctly. Apply a sequence to move the edges, repeat if necessary. (this is a little tricky, when you apply the sequence one block stay and 3 blocks move)

The only remaining cubes are the 4 corners. They can be all scrambled up!

Next we apply a sequence so that all four top corners are at the right position, color doesn't matter now (repeat sequence if necessary).

Now the last step, with red facing front, apply a sequence to fix each corner! Fix one and you mess up the rest of cube! Worry not, keep going! Fix all four corners (keep red facing you) and we are done!

How satisfying to be able to solve it!!

The sequences are difficult to remember, and it IS a lot of moves. How did those people solve it in little more than 20 seconds? How did they do it blindfold?! Ah, the method in the booklet is just the beginner's method.

On my own, I am never even able to solve just 1 side without the solution. I have NO clue how did they come up with the solutions.

Nowadays it is not just solution booklets, there are websites that you can literally put color of each face and a solution will crank out for you! There are even detailed demos on youtube!

The cube is no longer impossible to solve!

However, it will take me a while to practice and remember the patterns it takes to solve one.

Last thought: when you buy a Rubik cube,it is perfect condition, all sides are arranged properly. Why did you mess it up in the first place and want to put it back the way it was?

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