I am Bob Burton, Rubik's Cube Expert, and I am teaching you how to solve a Rubik's Cube. Now that we have the first two layers completely solved and we have the last layer oriented, we need to permute the edges of the Rubik's cube. To solve this we need to first put the edges in such a way that one of them is correctly permuted. That means that one of them will line up with the correct center. If we rotate the Rubik's cube so that we have that, notice that the other three are wrong. If we have two edges that are correct, and that's the only way that we can have the correct edges, then we have more to do. First I will show you the easy case. If one of them is correct, we're going to move to right side down twice, the top side to the left. We then go right side up, top side left, right side down, top side right. You have seen that part before in a different algorithm. We then go right side down, top to the right, right side down, top to the left, right side down. That completely solves the last layer edges of the Rubik's cube.
Sometimes it's possible that no matter what we do we have either zero or two edges correct. That happens when the Rubik's cube edges are correct across from each other. If that's the case, we first do the algorithm pretending that only one of them is correct. Right side down twice, top to the left, up, left, down, right, down, right, down, left, down. Now, we can arrange the Rubik's cube so that we have, again, only one correct. We put the correct piece in the back always. We then do the algorithm that we already know; down twice, left, up, left, down, right, down, right, down, left, down. Notice that we still have one correct. What it does is it cycles three corners, three edges clockwise. Sometimes since we're rotating three edges, we need to do it twice. This is one of those cases. Down twice, left, up, left, down, right, down, right, down, left, down. We're now ready to move on to the last step, permuting the last layer corners of the Rubik's cube.
