felipero

class ArrayTools
  def self.flat_array(array = [])
    array.each_with_object([]) do |item, flat_array|
      next if item.kind_of? String
      flat_array.push *(item.kind_of?(Array) ? flat_array(item) : item)
    end
  end
end

felipero

class BracketsChecker

  OPENING = ['[', '{', '(']
  CLOSING_MAP = {'[' => ']', '{' => '}', '(' => ')'}

  def valid?(input)
    return false if input.empty?
    open_brackets = []
    input.each_char do |char|
      open_brackets << char if OPENING.include? char