class Counter

# File lib/counter.rb, line 2
def initialize(other = nil)
  super(0)
  other.each { |e| self[e] += 1 } if other.is_a? Array
  other.each { |k, v| self[k] = v } if other.is_a? Hash
  other.each_char { |e| self[e] += 1 } if other.is_a? String
end

# File lib/counter.rb, line 9
def +(rhs)
  raise TypeError, "cannot add #{rhs.class} to a Counter" unless rhs.is_a? Counter

  result = Counter.new(self)
  rhs.each { |k, v| result[k] += v }
  result
end

# File lib/counter.rb, line 17
def -(rhs)
  raise TypeError, "cannot subtract #{rhs.class} to a Counter" unless rhs.is_a? Counter

  result = Counter.new(self)
  rhs.each { |k, v| result[k] -= v }
  result
end

# File lib/counter.rb, line 34
def inspect
  to_s
end

# File lib/counter.rb, line 25
def most_common(n = nil)
  s = sort_by { |_k, v| -v }
  n ? s.take(n) : s
end

# File lib/counter.rb, line 30
def to_s
  "Counter(#{super})"
end