ranking.rb

def rank(arr)
  count = {}
  arr.each{|item| count[item] = (count[item]||0) + 1}
  rank = 1 # initial ranking
  ranking = {}
  count.keys.sort.reverse.each{|item| ranking[item] = rank; rank += count[item]}
  arr.map{|item| ranking[item]}
end


raise 'code fail!' unless rank([5, 5, 5, 5, 5, 1, 1, 1, 1, 1]) == [1, 1, 1, 1, 1, 6, 6, 6, 6, 6]

ds = []
array_size = 100_000
array_size.times do |n|
  ds << rand(n)
end

now = Time.now
rank(ds)
puts "time elapsed: #{Time.now - now}"
# ruby 1.9.1 on my machine: 0.112s