crazy_merging.rb

  icons = Hash.new
  @vehicles.each do |v|
    if !v.latest_position.nil?
    icon = v.icon_id || 0
    heading = v.latest_position.heading
    if icons.has_key?(icon)
      if icons[icon].has_key?(heading)
        icons[icon][heading].push(v)
      else
        icons[icon][heading] = [v]
      end
    else
      icons[icon] = Hash.new
      icons[icon][heading] = [v]
    end
    end
  end

  gmax = 2
  key_count = [gmax, icons.keys.length].max
  while icons.values.collect{|v| v.length}.inject(0){|sum,item| sum + item} > key_count:
    # Identify who gets combined based on which two nodes are the closest in value (lowest diff)
    diff = 360  # Hold the difference for an in-place identification
    icon = nil # The "icon" we're going to reduce
    place = [] # The two heading values that will be combined
    icons.each do |key, value|
      headings = value.keys
      headings.sort!
      for i in (1...(headings.length)) do
        t_diff = headings[i] - headings[i-1]
        if t_diff < diff
          diff = t_diff
          icon = key
          place = [headings[i-1], headings[i]]
        end
      end
    end

    # Now do the reduce step.
    new_heading = ((place[0] + place[1])/2).to_i
    combined = icons[icon][place[0]] + icons[icon][place[1]]
    icons[icon].delete(place[0])
    icons[icon].delete(place[1])
    icons[icon][new_heading] = combined
  end

The problem is that Google Static Maps only lets you have GMAX custom icons on the map at a time. We have N shuttles to graph, and each has an icon assigned by it's heading. Each shuttle can also be assigned a different colored icon. For simplicity purposes, we assume there are never more than GMAX colors in use (because I don't know how to reduce colors).

The icon data-structure is a two level hash (color > heading) holding an array, that looks like this:

• red:
• - 90: [bus 1, bus 2]
• - 100: [bus 3, bus 4]
• blue:
• - 10: [bus 5]

The idea is to reduce this dataset to GMAX color-heading pairs, so from red-90, red-100, blue-10 to something like red-95, blue-10.