# How do I solve the C4Y 3x3x7?

I have been solving the Rubik's Cube 2x2x2, 3x3x3, 4x4x4 and 5x5x5, and because things are very similar I thought a 6x6x6 wouldn't be a challenge much. So I bought the C4U 3x3x7 - see image. What I want to know is how to solve it, what algorithms do I need? I can't find any good YouTube tutorials and also not a good website with algorithms and explanation on how to solve it.

What I found in the tutorials are the next few steps, the first steps I can follow but steps 4 to the end not:

2. Solve the middle layer with the normal blocks
3. Make sure the upper and bottom layer pieces are aligned correctly so you can turn it. (left image)
4. ???
5. Profit

Where do I go from here?

• 5. Profit!!!!!!
– SQB
May 26, 2014 at 7:56

I used to have this puzzle, but now I don't. I apologize if these instructions have a few holes in them - they should be complete, though, as I tested them on a 3x3.

The general method for solving this puzzle is:

• Solve the middle layer pieces (as you've done)
• Rotate the top corners and edges so that the slices are turnable (as you've also done)
• Solve the closest two layers to the middle that are not yet solved
• If need be, reorient the middle layer so that it is in line with the outside unsolved layers.
• After they are solved, consider them to be part of the middle layer. This is important.
• Advance to the next closest outside layer.

The first point of note is that you should leave the cube oriented in one direction for the entire solve, unless you've actively identified that the middle layer is solved. If you don't, you might unintentionally mess it up.

The second point of note is that U and D apply only to the depth of layer that isn't solved. For instance, if you've solved the inside layers on both the top and bottom, U and D only tell you to rotate the top and bottom two layers. Or, phrased differently, once you're done solving the bottom and top layers from the inside out, don't rotate them again. So, if you're trying to solve pieces on the second layer, don't rotate the third layer as well.

Orient the cube so that the rotating sides are facing up and down. These form your bottom and top layers.

Bottom layer

• First, solve the bottom-layer edges by intuition. This isn't difficult once you get used to it.
• Second, solve the corners by basic substitution with the corners on the top layer.

The first thing to do is solve the bottom edges by intuition. You can swap any edges with just the right-face rotations. For instance, if I wanted to swap the F and R edges, I would move R2 U' R2 D R2 U R2 D' U' R2 - this may look like a lot, but really all I'm doing here is moving an edge out of position, then moving it back into position over the correct edge. Go through it slowly and watch how the pieces move. The setup positions are actually fairly straightforward.

Next, move the corners into place over the correct positions. Move the corners over the positions where they belong at the FR position, and execute the following sequence: R2 U R2 U' R2; this will move the corner into place. If you're in a situation where corners are all on the white face but in the wrong spots, just remove a white piece with a yellow one, and use the floating white corner to solve the others.

Top layer

• Solve the positions of the corners by swapping adjacent corners
• Solve the positions of the edges by swapping adjacent edges

Next, we want to solve the top layer corners. This uses one algorithm, and is pretty simple. First, rotate the top layer so as many corners as possible are solved. Identify corners which need to be flipped. Use the following algorithm to swap the two corners on the top-right side: (R2 U R2 U' R2) [U' D] (R2 U' R2 U R2) [D'].

If two corners need to be swapped diagonally, then execute this sequence:

• once, to place the two corners that need to be swapped next to each other
• once, to swap those two corners
• once, to undo the first swap

At this point, you need to solve the edges for the layers. The algorithm you need for this is: (R2 U)2 (R2 U2)2 R2 U R2 U' R2, which swaps two edges that are in the F and R positions. You may also wish to use (R2 U2)3, which swaps the F and B edges.

Middle layer

It happens \$50\%\$ of the time that two middle layer pieces may not be oriented correctly once you've solved a top and bottom layer. If this is the case, execute the following sequence: (R2 U2)3 Sw U Sw U', where Sw = (R2 U)2 (R2 U2)2 R2 U R2 U' R2.

To explain why this sequence works, note first that the algorithms that swap two edges also swap two middle pieces. The above algorithm is a combination of the following: first, swapping the F and B edges; second, swapping the F and L edges; third, swapping the L and B edges. This actually solves the edges, but it does so with three swaps, flipping the middle layer into the correct orientation.

Follow these steps for all three layers and your puzzle is solved.

• But with R2 U R2 U' R2 you change the middle layer, isn't that a problem? May 25, 2014 at 18:51
• @mart I don't think so - if I recall, the middle layer resolves itself. Let me look at my old algs again, though...
– user20
May 25, 2014 at 18:57
• you could first solve as a 3x3x3 looking only at top most, bottom most and middle layers May 26, 2014 at 10:29
• @martijnn I've just updated the answer to address your concerns (and hopefully make it clearer). Looks like you were right, actually. My mistake!
– user20
May 28, 2014 at 0:15
• @martijn I have just obtained my 3x3x7, and will probably update this answer later. Is there anything here which is confusing/unclear that you think I should improve? (I've got a better algorithm for flipping the middle layer, too.)
– user20
Jun 6, 2014 at 21:46

Solving the top layer
Emrakul has a good anwser, but the top layer takes a lot of time. To speed things up you can also use the following algorithm:

You can come in the situation that you only need to swap the F and R edge then you need the algorithm Emrakul suggested in his anwser.

(R2 U)2 (R2 U2)2 R2 U R2 U' R2

• Just bear in mind that executing these algorithms changes all the other pieces around, too - they're not compatible with a thin layer on the top and bottom. They do work, though, for the first two layers.
– user20
May 28, 2014 at 21:15
• These algorithms are designed to only change the cubies with the arrows. Uhmm I think I need to change this... Because it also change orientation ... May 28, 2014 at 21:48
• Well, what I meant by that is that it will change the positions of the other layers in the cubies. Since the cubies you'd be moving around now have three independently-rotating layers to them, any algorithm which uses R/L/F/B instead of R2/L2/F2/B2 can only swap entire blocks of three pieces, instead of just one layer.
– user20
May 28, 2014 at 23:56
• maybe you can add my thing to your post, than I will delete my answer :) What you want :) May 29, 2014 at 7:51
• You know, for a moment, I thought "anwser" was referring to something memetically.
– user88
Aug 2, 2014 at 4:18