Finding Optimal Solutions to Rubik's Cube Using Pattern Databases
How to solve the Google Doodle Rubik's Cube
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Today's Google Doodle marks the 40th anniversary of the Rubik's Cube: the toy and/or puzzle that has rapidly infuriated and then eternally haunted almost every person to have walked this fair Earth since the 1970s. While Google was obviously going for warm fuzzy nostalgia, I thought it was rather cruel to remind tens of millions of people of their intellectual inferiority with a playable Rubik's Cube Doodle. As one of the few people who can actually solve a Rubik's Cube, I feel like it's my duty to give you some tips on how to finally solve the three-dimensional puzzle that has probably tormented you since childhood. Read on, for how to solve Google's Rubik's Cube Doodle.
Know your Rubik's Cube
From the outset, the Rubik's Cube just looks down right intimidating. It looks like there are six different sides, composed of 54 colored tiles that can be moved and rotated in an almost infinite number of ways. In reality, a Rubik's Cube is actually much simpler. There are eight corner pieces, which can only be moved from corner to corner. There are 12 edge pieces, which can only be moved from edge to edge. And there are six central pieces that can be rotated in-place, but never moved.
This means that each face always has a predesignated color, and that the white side is always next to the orange side (for example). It also means each of the six faces can have a fixed designation (up, down, front, back, left, right). If the orange center piece is facing upwards, then the opposing red center piece is facing downwards — likewise, if the front face is white, then the back is yellow. It's useful to try and keep each face/color combination in your head.
Making your first moves: Solving the upper face
To solve the first Rubik's Cube face, pick one color to be "up" or "top." In the video above (which I highly recommend watching), orange is the top color. For the first face, most moves will only require one or two turns, to "flip" the colors of an edge or corner piece. As you can see in the video above, this normally involves twisting the side away from the top, making another perpendicular twist to flip the piece, and then twisting the side back towards the top.
At this point, I should tell you that there are lots of different ways of solving a Rubik's Cube. I suggest you try following the video above for your first attempt — but you may have to do a lot of pausing, while you try to assimilate all of the data. Once he starts making more complex moves, you will definitely want to pause a lot, or else you'll get lost very quickly. Another alternative is to follow a written guide, with diagrams. RuWix has a good guide, along with lots of other useful tools. HowToCube has another good guide, complete with easy-to-follow animations. If you get really stuck, you can use the online Rubik's Cube solver, where you can input your cube's colors, and then it generates a list of moves to solve it.
Eventually, if you want to proceed beyond the upper face and a few second-level pieces, you're going to have to start thinking algorithmically — fixed sets of moves that move pieces from one side to the other, without disrupting the pieces that are already in the right place. This is where solving a Rubik's Cube actually gets hard, and where you'll definitely want to read a guide or watch a video. I suggest you stick with one guide for at least 30 minutes before giving up and moving to another — mixing and matching guides will likely result in lots of frustration.
Most guides use the Singmaster notation for describing moves (LU'RU, etc.) but I recommend using Wolstenhome's notation instead. Wolstenhome's notation results in moves that sound more like words, which are generally much easier to remember.
In general, once you've worked out all of the moves (and as complex as they sound, there are really only a handful of moves that you need to memorize) the solving itself is fairly easy. Most Rubik's Cubes can be solved in around 100 moves — so, with a little practice, solving a cube in under a few minutes is actually quite feasible. Eventually, you might even solve it in around five seconds, like this guy (but I doubt it).
Other fun ways of solving a Rubik's Cube
This being ExtremeTech, I would be remiss if I didn't show you a few extreme, technological ways of solving a Rubik's Cube. To begin with, here's one of the first at-home robotic Rubik's Cube solvers — made using Lego Mindstorms no less.
And then, to show you just how far Mindstorms have come in the six years since, here's Cubestormer 3, which can solve a cube in around three seconds.
The main advantage that robots have is that they can seamlessly move multiple pieces at the same time. Human speedcubers can also manipulate multiple pieces at once, but not quite at the same scale as a robot. Robots are also perfectly suited because the fastest speedcubing algorithms only require one "look" — as in, by memorizing where all the pieces are in an unsolved cube, an exact set of moves can be generated that will solve the cube in one go.
And finally, even though it isn't technological at all (but it is extreme), here's a lunatic solving an 11x11x11 Rubik's Cube. No I won't teach you how to solve larger Rubik's Cubes. Life is too short.
Finding Optimal Solutions to Rubik's Cube Using Pattern Databases
Source: https://www.extremetech.com/extreme/182628-how-to-solve-the-google-doodle-rubiks-cube