Tuesday 28 December 2021

Solving a Rubik's Cube

We bought a Rubik's Cube while away on our summer holiday this year and spent some time playing around with it and then learning to solve it.  We've returned to it over the Christmas break.  The solve we're learning is based on a very detailed video (below) from Wired Magazine.  I'm at the stage where I can remember most of the solve shown in the video but haven't memorised the final few steps involving the algorithms to position the final corner pieces in the top layer.



Since the video is so long and detailed, when you're at the stage of being able to remember most of the solve, you just need a quick memory jogger rather than wading through the video (even though it has some nice chapter markings).  Hence, this post is my quick reference guide for the future.  I'll walk through the whole solve very briefly (use the video for the detail)...

Introduction

Learn the right trigger and left trigger moves (involves holding the cube correctly)

Learn cube notation (rotate the appropriate face clockwise from the point of view of you looking straight onto that face)

  • F = Front Face

  • B = Back

  • L = Left

  • R = Right Face

  • D = Downward Face

  • U = Upward Face

  • ‘ = Spin anti clockwise e.g. F’ = Front Face anti clockwise

  • 2 Spin twice e.g. F2 = Front Face rotates by 180 degrees (spun twice)

 

Solve the bottom layer

Video Link
  1. Make the daisy
    1. Position white edge pieces around the yellow centre
  2. Make a white cross on the bottom face
    1. Line up white edge stickers on the top face with their middle colour on the side face, rotate the twice to move the white sticker from the top face to the bottom face
    2. The white face should remain pointing down for the rest of the solve
  3. Position the bottom row corners
    1. Search for corner pieces in the top layer that have a white piece
      1. If found, match the non-white colour of the corner piece in the top layer (ignore the top face) with the coloured center.
      2. With the non-white coloured center facing you observe whether the white sticker is on the left or right side of the cube. If left, perform the left trigger; if right, perform the right trigger.
    2. If there are no white pieces in the top layer but you have one in the bottom layer. Determine if the white piece in the bottom layer is on the left or right and with the white piece facing you, perform the left or right trigger (depending on whether the white piece is on the left or right side of the cube). The white piece will now be on the top of the cube.
    3. If there are no white pieces in the top layer but you have one on the top face. Rotate the top face such that the white sticker is not opposite a white sticker on the bottom face i.e. the white sticker on the top face should be opposite a coloured sticker on the bottom face. Then reposition the sticker so it’s in the top layer.
      1. Perform the left or right trigger twice in succession if depending on whether the white sticker on the top face is on the left or right side of the cube.  Now refer to 3.1 to place the corner correctly onto the bottom face.

 

Solve the middle layer

  1. Search the top layer for edge pieces that do not have any yellow stickers (either on the edge face or the top face).  Then once found move that piece to the second layer.
    1. Rotate the top layer such that the sticker on the edge face is colour matched with its centre sticker.
    2. Examine the colour of the sticker on the top face of the edge piece you're moving, it should match the left or right centre stickers.
      1. If it matches the left then rotate the top face anti clockwise by 90 degrees (a U' in notation form) then perform a left trigger
      2. If it matches the right then rotate the top face clockwise by 90 degrees (a U in notation form) then perform a right trigger
    3. You've now displaced one of the white stickers.  It will be in the top row so simply place it back to the bottom face using the same method as when solving the bottom layer.
  2. Repeat the above until there are no more non-yellow stickers on the top face.
  3. You may occasionally find a situation where there are no edge pieces in the top layer without yellow stickers but the second layer is not complete.  If this happens:
    1. Examine the middle layer for the piece that is not right.  With that piece facing you, examine if it's on the left or right of the cube.  Perform either the left or right trigger according to which side its on.
    2. Fix the displaced white piece.
    3. There will now be an edge piece in the top layer that doesn't have a yellow sticker so continue solving as per the first step of the middle layer.
 

Create a Yellow Cross (top face)

Required Algorithm: F U R U' R' F'

  1. Repeat these steps depending on the number of yellow edge pieces (on the top face):
    1. If there are no yellow edge pieces (on the top face), perform the algorithm.
    2. If there are two yellow edge pieces in a line, orient the line so it faces up/down, perform the algorithm.
    3. If there are two yellow edge pieces next to each other, place them in the 12 and 9 position on the top face, perform the algorithm.
 

Solve the Yellow Face


Required Algorithm: R U R' U R U2 R'
  1. Look at the top (yellow) face and repeat these steps depending on the number of yellow corner pieces (on the top face):
    1. If there are zero or two yellow corner stickers, rotate the top face until there is a yellow sticker in the top right position of the left face, perform the algorithm.
    2. If there is one yellow corner sticker, rotate the top face until the corner sticker is in the bottom right position, perform the algorithm.
 

Position the Top Layer Corners

 
Required Algorithm: L' U R U' L U R' R U R' U R U2 R'

  1. Look at the top corner pieces of the top layer, repeat these steps:
    1. If there are no matching corner pieces, perform the algorithm.
    2. If one of the faces has matching corner pieces, place that face in the left hand so it's pointing left, perform the algorithm.
  2. When all of the corner pieces match, rotate the upper face so the corner pieces on each face match up with their centre colour.

Position the Top Layer Edges


Required Algorithm (Clockwise) i: F2 U R' L F2 L' R U F2
 
Required Algorithm (Anticlockwise) ii: F2 U' R' L F2 L' R U' F2

  1. If one of the sides is solved, face it away from you then look at the edge pieces on the remaining unsolved 3 sides
    1. Swap the edges clockwise, perform algorithm i
    2. Swap the edges anticlockwise, perform algorithm ii
  2. If none of the sides are solved, perform algorithm ii, reposition the cube to face the solved face away from you and then perform algorithm ii again.

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