most_common_letter_01.rb

def most_common_letter(string)
  h = Hash.new    
  characters = string.chars.each do |c|
    if (h[c].nil?) then
      h[c] = 1
    else
      h[c] = h[c]+1
    end
  end
  maxk = nil
  maxc = -1
  h.each do |k,v|
    if (v > maxc) then
      maxk = k
      maxc = v
    end
  end
  [maxk , maxc]
end