StringValidator

string_validator.rb

class StringValidator
  ALLOWED_PARANTHESIS = {
    ')' => '(',
    '}' => '{',
    ']' => '['
  }.freeze

  def initialize(value = '')
    @text = value
  end

  def valid?
    !@text.empty? && balanced?
  end

  private

  def balanced?
    bracket_stack = []
    @text.each_char do |char|
      if ALLOWED_PARANTHESIS.value?(char)
        bracket_stack << char
      elsif ALLOWED_PARANTHESIS.key?(char)
        return false unless bracket_stack.pop == ALLOWED_PARANTHESIS[char]
      else
        # has only other matching parenthesis in between
        return false
      end
    end
    bracket_stack.empty?
  end
end

loop do
  puts 'Enter the input string: (type "exit" to leave)'
  input = gets.chomp
  break if input == 'exit'
  string = StringValidator.new(input)
  # String just because of the required output is 'True' and 'False'
  puts string.valid? ? 'True' : 'False'
end

> ruby validate_string.rb

#=> Enter the input string: (type "exit" to leave)
#=> ()[]{}
#=> True
#=> Enter the input string: (type "exit" to leave)
#=> ([{}])
#=> True
#=> Enter the input string: (type "exit" to leave)
#=> ([]{})
#=> True
#=> Enter the input string: (type "exit" to leave)
#=> ([)]
#=> False
#=> Enter the input string: (type "exit" to leave)
#=> ([]
#=> False
#=> Enter the input string: (type "exit" to leave)
#=> [])
#=> False
#=> Enter the input string: (type "exit" to leave)
#=> ([})
#=> False
#=> Enter the input string: (type "exit" to leave)
#=> exit