Rubik's Cube Picture

Rubik's Cube Picture

Thursday, December 15, 2011

Algorithms


In Rubik's cubists' parlance, a memorised sequence of moves that has a desired effect on the cube is called an algorithm. This terminology is derived from the mathematical use of algorithm, meaning a list of well-defined instructions for performing a task from a given initial state, through well-defined successive states, to a desired end-state. Each method of solving the Rubik's Cube employs its own set of algorithms, together with descriptions of what the effect of the algorithm is, and when it can be used to bring the cube closer to being solved.
Most algorithms are designed to transform only a small part of the cube without scrambling other parts that have already been solved, so that they can be applied repeatedly to different parts of the cube until the whole is solved. For example, there are well-known algorithms for cycling three corners without changing the rest of the puzzle, or flipping the orientation of a pair of edges while leaving the others intact.
Some algorithms have a certain desired effect on the cube (for example, swapping two corners) but may also have the side-effect of changing other parts of the cube (such as permuting some edges). Such algorithms are often simpler than the ones without side-effects, and are employed early on in the solution when most of the puzzle has not yet been solved and the side-effects are not important. Towards the end of the solution, the more specific (and usually more complicated) algorithms are used instead, to prevent scrambling parts of the puzzle that have already been solved.

Center Faces


The original Rubik's Cube had no orientation markings on the centre faces (although some carried the words "Rubik's Cube" on the centre square of the white face), and therefore solving it does not require any attention to orienting those faces correctly. However, with marker pens, one could, for example, mark the central squares of an unscrambled Cube with four coloured marks on each edge, each corresponding to the colour of the adjacent face. Some Cubes have also been produced commercially with markings on all of the squares, such as the Lo Shu magic square or playing cardsuits. Thus one can nominally solve a Cube yet have the markings on the centres rotated; it then becomes an additional test to solve the centres as well.
Marking the Rubik's Cube increases its difficulty because this expands its set of distinguishable possible configurations. When the Cube is unscrambled apart from the orientations of the central squares, there will always be an even number of squares requiring a quarter turn. Thus there are 46/2 = 2,048 possible orientations of the centre squares in the otherwise unscrambled position, increasing the total number of possible Cube permutations from 43,252,003,274,489,856,000 (4.3×1019) to 88,580,102,706,155,225,088,000 (8.9×1022).[22]
When turning a cube over is considered to be a change in permutation then we must also count arrangements of the centre faces. Nominally there are 6! ways to arrange the six centre faces of the cube, but only 24 of these are achievable without disassembly of the cube. When the orientations of centres are also counted, as above, this increases the total number of possible Cube permutations from 88,580,102,706,155,225,088,000 (8.9×1022) to 2,125,922,464,947,725,402,112,000 (2.1×1024).

Algorithms


In Rubik's cubists' parlance, a memorised sequence of moves that has a desired effect on the cube is called an algorithm. This terminology is derived from the mathematical use of algorithm, meaning a list of well-defined instructions for performing a task from a given initial state, through well-defined successive states, to a desired end-state. Each method of solving the Rubik's Cube employs its own set of algorithms, together with descriptions of what the effect of the algorithm is, and when it can be used to bring the cube closer to being solved.
Most algorithms are designed to transform only a small part of the cube without scrambling other parts that have already been solved, so that they can be applied repeatedly to different parts of the cube until the whole is solved. For example, there are well-known algorithms for cycling three corners without changing the rest of the puzzle, or flipping the orientation of a pair of edges while leaving the others intact.
Some algorithms have a certain desired effect on the cube (for example, swapping two corners) but may also have the side-effect of changing other parts of the cube (such as permuting some edges). Such algorithms are often simpler than the ones without side-effects, and are employed early on in the solution when most of the puzzle has not yet been solved and the side-effects are not important. Towards the end of the solution, the more specific (and usually more complicated) algorithms are used instead, to prevent scrambling parts of the puzzle that have already been solved.

Rubik's Cube Patterns

[Pons asinorum]
Pons asinorum
F2 B2 R2 L2 U2 D2(12q*, 6f*)

[Checkerboards of order 3]
Checkerboards of order 3
F B2 R' D2 B R U D' R L' D' F' R2 D F2 B'(20q*, 16f*)

[Checkerboards of order 6]
Checkerboards of order 6
R' D' F' D L F U2 B' L U D' R' D' L F L2 U F'(20q*, 18f)
R2 L2 U B L2 D' F B2 R L' F' B R D F2 L' U'(17f*, 22q)

[Stripes]
Stripes
F U F R L2 B D' R D2 L D' B R2 L F U F(20q*, 17f*)

[Cube in a cube]
Cube in a cube
F L F U' R U F2 L2 U' L' B D' B' L2 U(18q*, 15f*)

[Cube in a cube in a cube]
Cube in a cube in a cube
U' L' U' F' R2 B' R F U B2 U B' L U' F U R F'(20q*, 18f)
F' U B' R' U F2 U2 F' U' F U2 D B' D' R2 B2 U'(17f*, 22q)

[Christman's cross]
Christman's cross
U F B' L2 U2 L2 F' B U2 L2 U(16q*, 11f*)

[Plummer's cross]
Plummer's cross
R2 L' D F2 R' D' R' L U' D R D B2 R' U D2(20q*, 16f*)

[Anaconda]
Anaconda
L U B' U' R L' B R' F B' D R D' F'(14q*, 14f*)

[Python]
Python
F2 R' B' U R' L F' L F' B D' R B L2(16q*, 14f*)

[Black Mamba]
Black Mamba
R D L F' R L' D R' U D' B U' R' D'(14q*, 14f*)

[Green Mamba]
Green Mamba
R D R F R' F' B D R' U' B' U D2(14q*, 13f*)

[Female Rattlesnake]
Female Rattlesnake
U2 D' L2 D B U B' R' L2 U2 F U' F R(18q*, 14f*)

[Male Rattlesnake]
Male Rattlesnake
R' F' U F' U2 R L2 B U' B' D' L2 U2 D(18q*, 14f*)

[Female Boa]
Female Boa
R U' R2 U2 F D2 R2 U' D' R D' F'(16q*, 12f*)

[Male Boa]
Male Boa
F D R' U D R2 D2 F' U2 R2 U R'(16q*, 12f*)

[Four spot]
Four spot
F2 B2 U D' R2 L2 U D'(12q*, 8f*)

[Six spot]
Six spot
U D' R L' F B' U D'(8q*, 8f*)

[Orthogonal bars]
Orthogonal bars
F R' U L F' L' F U' R U L' U' L F'(14q*, 14f*)

[Six T's]
Six T's
F2 R2 U2 F' B D2 L2 F B(14q*, 9f*)

[Six-two-one]
Six-two-one
U B2 D2 L B' L' U' L' B D2 B2(15q*, 11f*)

[Exchanged peaks]
Exchanged peaks
F U2 L F L' B L U B' R' L' U R' D' F' B R2(19q*, 17f)
F2 R2 D R2 U D F2 D' R' D' F L2 F' D R U'(16f*, 21q)

[Two twisted peaks]
Two twisted peaks
F B' U F U F U L B L2 B' U F' L U L' B(18q*, 17f)
F D2 B R B' L' F D' L2 F2 R F' R' F2 L' F'(16f*, 20q)

[Four twisted peaks]
Four twisted peaks
U' D B R' F R B' L' F' B L F R' B' R F' U' D(18q*, 18f*)

[Exchanged chicken feet]
Exchanged chicken feet
F L' D' B' L F U F' D' F L2 B' R' U L2 D' F(19q*, 17f*)

[Twisted chicken feet]
Twisted chicken feet
F L' D F' U' B U F U' F R' F2 L U' R' D2(18q*, 16f*)

[Exchanged rings]
Exchanged rings
B' U' B' L' D B U D2 B U L D' L' U' L2 D(18q*, 16f)
F U D' L' B2 L U' D F U R2 L2 U' L2 F2(15f*, 20q)

[Twisted rings]
Twisted rings
F D F' D2 L' B' U L D R U L' F' U L U2(18q*, 16f*)

[Edge hexagon of order 2]
Edge hexagon of order 2
U B2 U' F' U' D L' D2 L U D' F D' L2 B2 D'(20q*, 16f*)

[Edge hexagon of order 3]
Edge hexagon of order 3
D L' U R' B' R B U2 D B D' B' L U D'(16q*, 15f)
F L B U L F2 B2 R' F2 B2 U' B' L' F'(14f*, 18q)

[Tom Parks' pattern]
Tom Parks' pattern
L U F2 R L' U2 B' U D B2 L F B' R' L F' R(20q*, 17f*)

[Ron's cube in a cube]
Ron's cube in a cube
F D' F' R D F' R' D R D L' F L D R' F D'(17q*, 17f)
L2 D2 L' D2 B2 L2 B2 L' D2 L2 B2 L' B2(13f*, 23q)

[Twisted duck feet]
Twisted duck feet
F R' B R U F' L' F' U2 L' U' D2 B D' F B' U2(20q*, 17f*)

[Exchanged duck feet]
Exchanged duck feet
U F R2 F' D' R U B2 U2 F' R2 F D B2 R B'(21q*, 16f*)

Math Behing the Rubik's Cube


The original (3×3×3) Rubik's Cube has eight corners and twelve edges. There are 8! (40,320) ways to arrange the corner cubes. Seven can be oriented independently, and the orientation of the eighth depends on the preceding seven, giving 37 (2,187) possibilities. There are 12!/2 (239,500,800) ways to arrange the edges, since an odd permutation of the corners implies an odd permutation of the edges as well. Eleven edges can be flipped independently, with the flip of the twelfth depending on the preceding ones, giving 211 (2,048) possibilities.[20]
 {8! \times 3^7 \times 12!/2 \times 2^{11}} = 43,252,003,274,489,856,000
which is approximately forty-three quintillion.[21]
The puzzle is often advertised as having only "billions" of positions, as the larger numbers are unfamiliar to many. To put this into perspective, if one had as many 57-millimeter Rubik's Cubes as there are permutations, they could cover the Earth's surface 275 times.
The preceding figure is limited to permutations that can be reached solely by turning the sides of the cube. If one considers permutations reached through disassembly of the cube, the number becomes twelve times as large:
 {8! \times 3^8 \times 12! \times 2^{12}} = 519,024,039,293,878,272,000.
which is approximately five hundred and nineteen quintillion[21] possible arrangements of the pieces that make up the Cube, but only one in twelve of these are actually solvable. This is because there is no sequence of moves that will swap a single pair of pieces or rotate a single corner or edge cube. Thus there are twelve possible sets of reachable configurations, sometimes called "universes" or "orbits", into which the Cube can be placed by dismantling and reassembling it.

Centre

Other Cubes


There are different variations of Rubik's Cubes with up to seven layers: the 2×2×2 (Pocket/Mini Cube), the standard 3×3×3 cube, the 4×4×4 (Rubik's Revenge/Master Cube), and the 5×5×5 (Professor's Cube), the 6×6×6 (V-Cube 6), and 7×7×7 (V-Cube 7).
CESailor Tech's E-cube is an electronic variant of the 3×3×3 cube, made with RGB LEDs and switches.[46] There are two switches on each row and column. Pressing the switches indicates the direction of rotation, which causes the LED display to change colours, simulating real rotations. The product was demonstrated at the Taiwan government show of college designs on October 30, 2008.
Another electronic variation of the 3×3×3 Cube is the Rubik's TouchCube. Sliding a finger across its faces causes its patterns of coloured lights to rotate the same way they would on a mechanical cube. The TouchCube was introduced at theAmerican International Toy Fair in New York on February 15, 2009.[47][48]
The Cube has inspired an entire category of similar puzzles, commonly referred to as twisty puzzles, which includes the cubes of different sizes mentioned above as well as various other geometric shapes. Some such shapes include thetetrahedron (Pyraminx), the octahedron (Skewb Diamond), the dodecahedron (Megaminx), the icosahedron (Dogic). There are also puzzles that change shape such as Rubik's Snake and the Square One.

Rubik's Cube World Record Times

 
 
TypeResultPersonCitizen ofCompetitionResult Details
 
Rubik's Cube
Single5.66Feliks ZemdegsAustraliaMelbourne Winter Open 2011 
Average7.64Feliks ZemdegsAustraliaMelbourne Winter Open 20117.03   8.11   8.36   5.66   7.78
 
4x4 Cube
Single30.28Feliks ZemdegsAustraliaAustralian Nationals 2011 
Average35.22Feliks ZemdegsAustraliaWorld Championship 201133.33   38.71   33.28   33.63   39.33
 
5x5 Cube
Single56.22Feliks ZemdegsAustraliaWorld Championship 2011 
Average59.94Feliks ZemdegsAustraliaWorld Championship 201159.59   58.41   1:01.81   1:05.40   56.22
 
2x2 Cube
Single0.69Christian KasererItalyTrentin Open 2011 
Average2.12Feliks ZemdegsAustraliaMelbourne Cube Day 20102.38   1.77   1.75   2.21   2.46
 
Rubik's Cube: Blindfolded
Single30.58Yuhui Xu (许宇辉)ChinaSuzhou Open 2011 
 
Rubik's Cube: One-handed
Single10.68Piotr TomczykPolandSwierklany Open 2011 
Average13.57Michał PleskowiczPolandWorld Championship 201112.34   15.83   12.97   15.11   12.63
 
Rubik's Cube: Fewest moves
Single22Jimmy CollBelgiumBarcelona Open 2009 
  István KoczaHungaryCzech Open 2010 
 
Rubik's Cube: With feet
Single31.56Anssi VanhalaFinlandHelsinki Open 2011 
Average39.98Anssi VanhalaFinlandKotka Open 201137.81   39.30   42.84
 
Megaminx
Single42.28Simon WestlundSwedenDanish Open 2011 
Average49.90Simon WestlundSwedenDanish Open 201149.46   49.30   48.61   52.44   50.94
 
Pyraminx
Single1.93Yohei Oka (岡 要平)JapanJapan Open 2011 
Average3.39Yohei Oka (岡 要平)JapanKyotanabe Open 20113.65   2.86   2.75   3.65   4.59
 
Square-1
Single8.65Bingliang Li (李炳良)ChinaGuangdong Open 2010 
Average11.33Bingliang Li (李炳良)ChinaChangsha Open 201111.83   14.13   11.44   10.72   10.11
 
Rubik's Clock
Single5.83Javier Tirado OrtizSpainWorld Championship 2011 
Average7.33Sam Zhixiao Wang (王志骁)ChinaGuildford Summer Open 201111.30   6.78   8.15   5.88   7.05
 
6x6 Cube
Single1:54.81Kevin HaysUSAVancouver Winter 2011 
Average2:02.13Kevin HaysUSAVancouver Winter 20112:00.93   1:54.81   2:10.66
 
7x7 Cube
Single3:13.19Michał HalczukPolandPolish Nationals 2011 
Average3:25.10Michał HalczukPolandSwierklany Open 20113:17.97   3:31.68   3:25.66
 
Rubik's Magic
Single0.69Yuxuan Wang (王宇轩)ChinaBeijing Spring 2011 
Average0.76Yuxuan Wang (王宇轩)ChinaBeijing Summer Open 20110.72   0.77   0.77   0.75   DNF
 
Master Magic
Single1.68Ernie PulchnyUSAPark Ridge Open 2011 
Average1.75Ernie PulchnyUSAUS Nationals 20111.78   1.71   1.77   1.71   3.08
 
4x4 Cube: Blindfolded
Single3:26.11Daniel SheppardUnited KingdomGuildford Summer Open 2011 
 
5x5 Cube: Blindfolded
Single9:48.58Ville SeppänenFinlandKirkkonummi Open 2011 
 
Rubik's Cube: Multiple Blindfolded
Single23/25 57:48Zane CarneyAustraliaMelbourne Cube Day 2011 

Rubik's Cube Facts


  • Ernö Rubik invented the Cube in the spring of 1974 in his home town of Budapest, Hungary. He wanted a working model to help explain three-dimensional geometry and ended up creating the world's best selling toy.
  • Rubik's inspiration for the Cube's internal mechanism came from pebbles in the River Danube whose edges had been smoothed away.
  • Rubik called his invention the 'Magic Cube'. It was renamed the Rubik's Cube by the Ideal Toy Corporation in 1980.
  • More than 300 million Rubik's Cubes have been sold worldwide. If all the cubes were placed on top of each other it would be enough to reach the North Pole from the South Pole!
  • At the height of the Rubik's craze in the mid-1980s, it was estimated that one-fifth of the world's population had played the Cube.
  • 'Cubing' still infects people of all ages. 'Cubaholics' are said to suffer from 'Rubik's wrist' and 'Cubist's thumb'!
  • Rubik's Cube has featured in hundreds of books, magazines, movies and even had its own TV series on ABC in America. Millions of web pages, blogs and YouTube videos are now dedicated to cubing.
  • The Cube has inspired everything from fashion, architecture and music to films, plays and political speeches. There is also a dedicated art movement known as 'Rubikubism'.
  • There are edible cubes, jewel-encrusted Cubes and even MP3 playing cubes! The biggest Cube in the world, on display in Knoxville, Tennessee, is 3 metres tall and weighs over 500kg.
  • National and international 'speedcubing' championships have been held regularly since 2003. The World Cube Association now runs competitions where players have to solve the Cube one-handed, as well as having to solve the Cube using only your feet. There is even a competition where players have to solve the Cube as quickly as possible blindfolded!
  • In May 2007, Thibaut Jacquinot of France became the first person to complete the Cube in under 10 seconds in open competition, setting a world record time of 9.86 seconds. The current world record for a single solve was set in June 2011 at the Melbourne Winter Open competition in Australia, by Feliks Zemdegs with an incredible time of 5.66 seconds!!
  • The speed Cubing Championships were held in Budapest in October 2007 and were attended by Ernö Rubik himself.
  • In 2007 the Rubik's Cube beat stiff competition to be recognised in the annual CoolBrands list by the Superbrands organisation.

How To Solve A Rubik's Cube

Rubik's Cube Introduction
There are many different methods for solving the Rubik's cube. They can be divided into two broad categories: layer methods and corners first methods (and there are sub-categories within these broad categories). The method I use for speedsolving is a layer based method. More specifically, the method I currently use is: cross, F2L, 3-look LL (I know some of the OLLs, so sometimes I can do a 2-look LL). If you are a newbie cuber then this description may not mean much to you, so I should add that it's the 'Advanced Solution' I described in the Next Steps section at the end of this page.
Many years ago when I wrote this webpage there were many great websites that explained advanced and expert methods for solving the cube (check out my Rubiks links page), however, there were very few that explained beginner methods. This is the reason I wrote this page. It's not meant to be a totally comprehensive explanation, it's really just some notes I threw together for some friends I was teaching. I thought it might be useful for others, so I've turned it into a webpage.
This beginner method requires memorising only a few algorithms, and when done efficiently can achieve solves of 60 seconds or faster. I know people who can solve in 20-30s with a method like this. I haven't been able to solve so fast with a beginner method, so don't be too distressed if you can't either. On the other hand, if you can do 30s solves with this method, then you are too good for this method and you should be learning an Advanced or Expert method!
Aside from minimal memorisation, another benefit of this method is that it is very scalable. More algorithms may be added later to develop it into an advanced method, or if you're really keen, an expert method. This means you don't need to scrap it and start again to move to an expert method. Everything you learn here will be useful for more advanced methods.
Rubik's Cube Structure of the cube
We all know that 3x3x3=27, however, rather than thinking about the cube as 27 little "cubies", think about it as 6 fixed centres (that can rotate on their own axis) with 8 corners and 12 edges which rotate around it. As the centres are fixed, the centre colour defines the colour for the face. It's important to remember this otherwise you'll end up trying to do illogical (mechanically impossible!) things like wondering why you can't work out how to put a corner piece in an edge position, or assuming that you're looking at the blue face merely because 8 of the 9 cubies on it are blue (if the centre is white then it's the white face).
Rubik's Cube Terminology
When describing the solution for the 2nd and 3rd layers, standard cube notation will be used. Here's what you need to know to read it:
F = front face
B = back face
R = right face
L = left face
U = up face
D = down face

In addition to a letter, each move may be accompanied by an apostrophe or the number two:
  • A letter by itself means turn that face 90 degrees clockwise (eg. F).
  • A letter followed by an apostrophe means turn that face 90 degrees anti-clockwise (eg. F').
  • A letter followed by the number 2 means turn that face 180 degrees (direction is irrelevant), (eg. F2).
So R U' L2 is shorthand for "turn the right face 90 degrees clockwise, then turn the up face 90 degrees anti-clockwise, then turn the left face 180 degrees". When thinking whether to turn clockwise/anti-clockwise, imagine that you are looking directly at the particular face you are turning.
For each algorithm, the notation is written with the assumption that the core of the cube remains fixed throughout the whole algorithm, and the faces just turn around it. This means that you also need to know how to position the cube to start the algorithm.
For pictures and further detail about cube notation, have a look at Jon Morris' cube notation page.


The Solution

Rubik's Cube The First Layer

The first layer is solved in two stages:
  1. Form the cross
  2. Insert the 4 first layer corners (each corner is inserted individually)
I believe that the first layer should be done intuitively. You need to understand it and solve it without learning algorithms. Until you can do this, I wouldn't bother attempting the rest of the cube! So, spend some time playing with the cube and familiarising yourself with how to move the pieces around the cube.
Now, here are some tips to get you started.
Rubik's Cube The Cross
I prefer to start with the white cross because I find white easier to quickly identify on a completely scrambled cube, however, you can use any colour.
There are 4 edge pieces with white (ie. the 4 arms of the cross) which have specific positions. You can't put any white edge piece in an arm of the cross because the other colour on the edge cubie must match up with it's centre on the middle layer.
cross: correct
Here is a pic of what a correctly formed cross looks like (grey denotes cubies that are irrelevant to the cross). Note that the white/red edge cubie matches up with the white centre and the red centre. Ditto re the white/blue cubie.
cross: incorrect
Here's a pic on an incorrectly formed cross. Looking at the white face we do indeed see a white cross, however the white/red edge cubie does not match up with the red centre. Ditto re the white/blue cubie. This is bad!

For a detailed explanation of the cross, check out Dan Harris' Solving the Cross page.
Rubik's Cube The First Layer Corners
Once you have completed the cross, completing the first layer requires inserting each of the 4 corners in separately. The first thing to do is examine your cube and locate all of the top layer edge pieces - they will be sitting in either the first layer or the last layer. Inserting the first layer corners should be done intuitively, not by learning algorithms. To get you started, here's a step-by-step example of one way to insert a first layer corner.
first layer corner: step 1
Step 1
The blue/red/white corner is sitting in the bottom layer (the blue part is facing the bottom so we can't see it in this picture). Turn the blueface 90 degrees anti-clockwise.
first layer corner: step 2
Step 2
Now your cube should look like this. Move the D face 90 degrees anti-clockwise to line up the blue/white edge with the blue/white/redcorner.
first layer corner: step 3
Step 3
Now that the blue/white edge and the blue/white/red corner have been lined up, re-form the white cross by turning the blue face 90 degrees clockwise.
first layer corner: step 4
Step 4
Now the blue/white/red corner is in its correct place.

Here are some tips for inserting the top layer corners:
  • Start with a first layer corner that is sitting in the last layer.
  • If there are multiple first layer corners in the last layer (there usually will be), start with one that does not have the white part of the corner on the face opposite the white face. Or, if you were using a different colour for the cross ('colour X'), start with a corner that does not have the 'colour X' part of the corner on the face opposite the 'colour X' face.
  • When working with a first layer corner piece that is in the first layer (but in the wrong first layer corner position), you will need to get it out of the first layer into the last layer, then insert it into the correct first layer corner position. The same principle applies if a first layer corner piece is in the correct first layer corner position but needs to be flipped around. You need to get it out of the first layer (ie. into the last layer), and then re-insert it into the first layer the correct way around.
completed first layer
This is what the first layer should look like when finished.

Rubik's Cube The Middle Layer

The middle layer consists of one stage:
  1. Insert the 4 middle layer edges (each edge is inserted individually).
You only need to learn one algorithm (plus the mirror algorithm) for the second layer. There are many more algs, but let's just learn the essential one first.
First, locate a middle layer edge that is currently sitting in the last layer. I'm going to use the blue/red edge for this example.
This blue edge cubie in the last layer is the blue/red edge cubie.
In this picture, U=white, L=red and F=blue. We can't see the other three faces, but obviously the R face is the one opposite the L face, the D face is opposite the U face and the B face is opposite the F face.
Now, position the blue/red edge piece so that the colour on the side of the cube (blue in this case) lines up with it's centre. Now perform the following algorithm: D L D' L' D' F' D F
If the blue/red edge piece was flipped the other way so that the blue was on the bottom rather than the red, you would position the cubie under the red centre and perform the following alg: D' F' D F D L D' L'. This is the mirror of the previous algorithm. The axis of symmetry lies diagonally across the white face, and along the line which divides the blue face and the red face.

What if the edge piece is not in the last layer?
The instructions above assume that the middle layer edge piece you are inserting is sitting somewhere in the last layer.
If some middle edges are in the last layer and some are in the middle layer in the wrong spot, always start working with the edge pieces that are in the last layer. After you've done this, sometimes (but not too often) you'll be left with a middle layer edge piece that's in the middle layer but in the wrong spot. In this situation, you can use the same middle layer algorithms from above (D L D' L' D' F' D F or D' F' D F D L D' L') to insert another edge piece into the middle layer edge position, thereby knocking the middle layer edge piece out of its spot and into the last layer. Once you've done this, the middle layer edge piece is in the last layer and you can deal with it in the usual way.
There is a short-cut to this problem, but as this is a beginner solution with minimal memorisation, I haven't included it here. If you really want to learn it, take a look at Case Dd2 on Dan Harris' site.
Middle layer edge in the wrong way
The red/blue middle layer edge piece is in the middle layer but not oriented correctly. It needs to be moved to the last layer, then put back into the middle layer in the right way.

Rubik's Cube The Last Layer

The last layer ("LL") is done in 4 steps:
  1. Orient the edges (2 algs) - i.e. form a cross on the D face.
  2. Permute the corners (1 alg) - i.e. get the corners in the correct position in 3D space (don't worry if they still need to be rotated).
  3. Orient the corners (1 alg + mirror alg) - i.e. flip the corners.
  4. Permute the edges (1 alg) - i.e. swap the edges around. The cube should now be solved! :)
All last layer algorithms are performed with the cross (i.e. the first layer - white side in this example) on the bottom.
Rubik's Cube Orienting the LL Edges
Once you have completed the first two layers ("F2L"), hold the cube so that the white side is on the bottom. The white side will be on the bottom for the remainder of the solution. This means that the white side is the D side for all last layer algorithms.
On my cube, white is opposite yellow, therefore yellow is the U face for all last layer algorithms on my cube. Note that your cube may have a different colour opposite white (e.g. blue). Now have a look at your last layer, and in particular, look at the last layer face - there are 4 possible patterns of LL edges that you may see.
State 1
State 2
State 3
State 4

Unlike with the initial cross (where all the edges must match up with the white centre and with the centres on the middle layer), here all you need to worry about is getting all the last layer edges matching up with the last layer centre. It doesn't matter if the other colour on the LL edge piece does not match up with the colour on the middle layer centre. Also, ignore the LL corners too. It doesn't matter what they are doing at the moment. Now, let's consider each of these LL edge states separately.
State 1
All the edges are already oriented correctly. Move on to permuting the corners.

State 2
We are going to re-orient our faces for this algorithm. The face you are looking directly at in this picture is now the U face (it was the D face for when you were doing the second layer edges). Perform the following algorithm: F U R U' R' F'

State 3
As with State 2, the face you are looking directly at in this picture is now the U face. Perform the following algorithm: F R U R' U' F'

State 4
State 4 is really a combination of States 2 and 3, so all you need to do is perform the algorithm for either State 2 or State 3. Once you've done this, you'll see that your LL edges now look like State 2 or State 3, so just perform the appropriate algorithm and you will have a cross on the LL.

Rubik's Cube Permuting the LL Corners
The two possible states are:
  • two adjacent LL corners need to be swapped; or
  • two diagonal LL corners need to be swapped.
These are the only two possible states. If you cannot identify one of these two states with your LL corners then one or more of the following must be true:
  • You have not finished the F2L.
  • Someone has ripped out a corner of your cube and put it in the wrong way.
  • Someone has ripped off some of your stickers and put them back in the wrong place.
  • You are not looking hard enough. ;)
Swapping adjacent corners
Hold the cube with the white side on the bottom, and the two corners to be swapped are in the front right top and the back right top positions. Perform the following algorithm: L U' R' U L' U' R U2. To see an animated version of this algorithm, see the first algorithm on Lars Petrus' Step 5 page. On Lars' site, the algorithm is being executed from a slightly different angle (the two corners being swapped are front-top-right and front-top-left), but it is the same exact algorithm.
Swapping diagonal corners
Swapping diagonal corners can be done by executing the adjacent corner swap algorithm twice. Perform it once to swap any two LL corners. Re-examine you cube and you'll see that now there are just two LL corners that need to be swapped. Position it correctly for the final LL adjacent corner swap and perform the LL adjacent corner swap algorithm.
Rubik's Cube Orienting the LL Corners
There are 8 possible orientation states for the LL corners. One is where all 4 corners are correctly oriented. The other 7 look like this.
State 1
State 2
State 3
State 4
State 5
State 6
State 7

State 1. Twisting three corners anti-clockwise
R' U' R U' R' U2 R U2

State 2. Twisting three corners clockwise
R U R' U R U2 R' U2
To see an animated version of this algorithm, look at Lars Petrus' Sune algorithm.

States 3-7
Once you know the algorithms for States 1 and 2, you can solve any LL orientation State. The remaining States can be oriented using a maximum of 2 algorithms. You will need to do one of the following (i) the State 1 algorithm twice, (ii) the State 2 algorithm twice, (iii) the State 1 algorithm, then the State 2 algorithm, or (iv) the State 2 algorithm, then the State 1 algorithm.
In a previous edition of this solution, I had said that I'm not going to tell you exactly how to combine the State 1 and State 2 algorithms to solve States 3-7. My reason for this was because it is important that you try to understand how the State 1 and the State 2 algorithms work, and that once you do understand them you will be able to work out how to use them to solve all the States. I still believe this, however, I received emails from a few people who were having trouble with States 3-7, so I decided to write some extra tips. I still suggest that you try to work out States 3-7 by yourself, but if you are really stuck, have a look here: Orienting the Last Layer Corners: further tips.
Rubik's Cube Permuting the LL Edges
There are 5 possible permutation states for the LL edges. One is where all 4 edges are correctly permuted. The other 4 look like this.
State 1
R2 U F B' R2 F' B U R2
State 2
R2 U' F B' R2 F' B U' R2 This is almost identical to the algorithm for State 1. Only difference is the 2nd move and the 2nd last move.
For an animated version of this algorithm, see the Lars Petrus' Allen algorithm. The algorithm is being executed from a slightly different angle, but it is the same exact algorithm.
State 3
Apply the algorithm for either State 1 or State 2. Re-examine your cube and it will now look like State 1 or State 2.
State 4
Apply the algorithm for either State 1 or State 2. Re-examine your cube and it will now look like State 1 or State 2.

And that's all you really need to know to solve the Rubik's Cube! With practice, you should be able to achieve times of 60 seconds (or faster) using this method. Once your comfortable with this method and want to learn more, take a look at the following section.

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Rubik's Cube Next Steps

If this beginner method is too easy and boring for you then consider the following.
Rubik's Cube Intermediate method
  • Solve each first layer corner + corresponding middle layer edge in one step. This means that after the cross you only have 4 steps (4 corner/edge pairs) to complete the F2L. With this beginner method there are 8 steps: solve each of the 4 first layer corners, then solve each of the 4 middle layer edges. I'd suggest just playing around with your cube and figuring out the F2L corner/edge pairs yourself. For some hints about solving the F2L intuitively, have a look at Doug Reed's intuitive F2L guide. If you're still stuck and just want the algorithms, check out Dan Harris' F2L page and Jessica Fridrich's F2L page.
     
  • Learn the 4 specific algorithms (or rather, 3 algorithms plus one mirror algorithm) for each of the 4 different permutation states of the LL edges. My beginner solution already shows you 2 of the 4 last layer edge permutation algorithms, the other two last layer edge permutation algorithms are Case #5 and Case #17 on Dan Harris' PLL page.
Rubik's Cube Advanced method
  • Learn everything from the Intermediate method.
  • Learn the 3-look LL. This requires learning the 7 specific algorithms for the 7 different orientation states of the LL corners, and learning the 21 PLL algorithms (permuting the last layer algorithms) so you can permute the LL edges and LL corners at the same time. A full 3-look LL uses 30 algorithms.
For more details about the advanced method, check out t Rubiks Galaxia 3-look LLDan Harris' site and Lars Vandenbergh's PLL page.
Rubik's Cube Expert method
  • Do the F2L in 5 steps (first dot point from the Intermediate method).
  • Learn a full 2-look LL. This requires memorising 21 PLL algorithms, plus 57 OLL algorithms (orienting the last layer algorithms).
For more details about the expert method, check out Dan Harris' siteJoël van Noort's site and Lars Vandenbergh's site.
Rubik's Cube Other stuff
The method I've documented here is what I believe to be a good beginner method. The problem with some beginner methods is that they are not scalable - to improve your cubing you have to un-learn much of what you know and re-learn it in a different way. This method focuses on memorising very few algorithms, but is structured in a way that allows for development into an intermediate or advanced method. Other thing I should say is that I didn't actually devise any of the last layer algorithms in this method. I merely chose a selection of existing algorithms (sourced from a variety of places including Jessica's site and Dan K's site) and organised them into a simple solution method.
Rubik's Cube Celebrate your cubing success!