Solution: Polar Grids with Uneven Row Heights

require 'polar_grid'
class UnevenPolarGrid < PolarGrid
# Write your code here
  def initialize(widths)
    # precompute some things to help `prepare_grid` and `to_png`
    # work a bit more smoothly.
    @widths = widths
    @radius = @widths.sum
    # the height (relative to the radius) of each row
    @row_heights = @widths.map { |width| width / @radius.to_f }
    # the inner radii of the rows
    @radii = Array.new(@widths.length + 1) { |i| @widths[0,i].sum }
    super(widths.length)
  end
# Mostly the same as the original, but look for where @radii
# and @row_heights are being used.
  def prepare_grid
    rows = Array.new(@rows)
    rows[0] = [ PolarCell.new(0, 0) ]
    (1...@rows).each do |row|
        relative_radius = @radii[row] / @radius.to_f
        circumference = 2 * Math::PI * relative_radius
        previous_count = rows[row - 1].length
        estimated_cell_width = circumference / previous_count
        ratio = (estimated_cell_width / @row_heights[row]).round
        cells = previous_count * ratio
        rows[row] = Array.new(cells) { |col| PolarCell.new(row, col) }
    end
    rows
  end
# Also mostly unchanged from before, but look for where @radius and
# @radii are introduced here!
  def to_png(cell_size: 10)
    img_size = 2 * @radius * cell_size
    background = ChunkyPNG::Color::WHITE
    wall = ChunkyPNG::Color::BLACK
    img = ChunkyPNG::Image.new(img_size + 1, img_size + 1, background)
    center = img_size / 2
    each_cell do |cell|
      next if cell.row == 0
      theta = 2 * Math::PI / @grid[cell.row].length 
      inner_radius = @radii[cell.row] * cell_size 
      outer_radius = @radii[cell.row + 1] * cell_size 
      theta_ccw = cell.column * theta
      theta_cw = (cell.column + 1) * theta
      ax = center + (inner_radius * Math.cos(theta_ccw)).to_i 
      ay = center + (inner_radius * Math.sin(theta_ccw)).to_i 
      bx = center + (outer_radius * Math.cos(theta_ccw)).to_i 
      by = center + (outer_radius * Math.sin(theta_ccw)).to_i 
      cx = center + (inner_radius * Math.cos(theta_cw)).to_i 
      cy = center + (inner_radius * Math.sin(theta_cw)).to_i
      dx = center + (outer_radius * Math.cos(theta_cw)).to_i
      dy = center + (outer_radius * Math.sin(theta_cw)).to_i 
      img.line(ax, ay, cx, cy, wall) unless cell.linked?(cell.inward) 
      img.line(cx, cy, dx, dy, wall) unless cell.linked?(cell.cw) 
    end
    img.circle(center, center, @radius * cell_size, wall)
    img
  end
end