【Ruby】【アルゴリズム】スタックを使った「括弧の対応を調べるプログラム」

Rubyは、クラスを再オープンできるところが面白いです。

でも眠いよ。

問題

３種類の括弧 (), {}, [] を含む文字列において，括弧の対応に整合性がとれているかどうかを判断する

解答

class Staple
  attr_accessor :column, :type
  def initialize( column, type )
    @column = column 
    @type = type
  end
end

class String
  def what_head_staple
    case self
      when ')'
        str = '('
      when '}'
        str = '{'
      when ']'
        str = '['
    end
    return str
  end
  def staple_check
    stack = []
    self.scan(/./).each_with_index do |char, i|
      if char.is_head_staple?
        staple = Staple.new(i , char)
        stack.push(staple)
        next
      end
      if char.is_end_staple?
        if stack.empty?
          return "column: " + i.to_s + " - the tag is not good" 
        elsif char.what_head_staple != stack.last.type
          return "column: " + i.to_s + " - the tag is not good"
        elsif
          stack.pop
        end
      end
    end
    if stack.empty?
      return "ok"
    else
      return "column: " + stack.first.column.to_s + " - the tag is not good"  
    end
  end 
  
  def is_head_staple?
    return true if self == '(' || self == '{' || self == '['
  end
  def is_end_staple?
    return true if self == ')' || self == '}' || self == ']'
  end
end

p "x(abc)".staple_check
p "x(abc}".staple_check
p "]x(abc)".staple_check
p "x(abc)}".staple_check
p "((abc)".staple_check

■実行結果

"ok"
"column: 5 - the tag is not good"
"column: 0 - the tag is not good"
"column: 6 - the tag is not good"
"column: 0 - the tag is not good"