gistfile1.txt

#!/usr/bin/env ruby

fh = File.new('rules3.csv', 'r')
ranges = []
range_counts = {}

while row = fh.gets
  row.chomp!
  company_id, rule_count = row.split(',')
  rule_count = rule_count.to_i
  range_top = ((rule_count + 99) / 100) * 100

  if !range_counts.has_key?(range_top)
    ranges << range_top
  end

  range_counts[range_top] ||= 0
  range_counts[range_top] += 1
end

ranges.each do |range_top|
  range_bottom = range_top - 100
  puts "#{range_bottom} - #{range_top}: #{range_counts[range_top]} customers"
end