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More Methods for Cube Mazes

More Methods for Cube Mazes

Learn a few more methods that will be added to the CubeGrid class.

We'll cover the following...

The CubeGrid class: A few more methods

Once we have that much, we reach the hardest part: determining cell adjacency. Specifically, we need to identify which cells are adjacent to which cells at the boundaries, and there are some remarkable edge cases here. We’ll set the basics up in the configure_cells and [] methods, like this:

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def configure_cells 
  each_cell do |cell|
    face, row, column = cell.face, cell.row, cell.column
    cell.west  = self[face, row, column-1]
    cell.east  = self[face, row, column+1]
    cell.north = self[face, row-1, column]
    cell.south = self[face, row+1, column]
  end 
end

The [] method

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  def [](face, row, column)
    return nil if face < 0 || face >= 6
    face, row, column = wrap(face, row, column)
    @grid[face][row][column]
  end

This should all look rather familiar, with the exception of the highlighted line in the array accessor method.

We’re going to add a new method, wrap, which takes the given face/row/column triple and—if the row or column overflows the face it’s on—figures out what the actual coordinates are on the face to which they’ve overflowed. This will allow the configure_cells method (discussed previously) to work as intended, where it simply adds or subtracts one from the row or column to get the correct neighbor, even if it extends to an adjacent face.

This is where the edge cases come in, but they aren’t all bad. Let’s start with an easy one. Consider our unfolded cube again and imagine moving from face 0, to 1, to 2, to 3, and back to 0. The transitions there are straightforward—we would go from the last column of one face to column 0 of the next face while remaining on the same row. Similarly, moving in reverse would take us from the first column of one face to the last column of the next. The following figure illustrates this:

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Moving from last column of one face to column 0 of the next face on an unfolded cube
Moving from last column of one face to column 0 of the next face on an unfolded cube

Easy enough. If only they could all be so straightforward! Let’s look at a trickier one: what happens when we move east ...