gistfile1.rb

list = [1, 1, 2, 2, 3]

# using each:
hash = {}
list.each do |item|
  hash[item] ||= 0
  hash[item] += 1
end


# using inject:
hash2 = list.inject({}) do |h, item|
  h.update(item => (h[item] || 0) + 1)
end