unzip.rb

# O(nk)
class Array
  def unzip ary
    return [] if ary.empty?
    count = ary.first.count
    (0...count).map { |i| 
      ary.map { |tuple| 
        raise 'inconsistent tuple size' if tuple.count != count
        tuple[i] 
      }
    }
  end
end

zipped = [[:a, 1], [:b, 2]]
zipped.unzip
#=> [[a, b], [1, 2]]