balance

balance.scala

  /**
   * Exercise 2
   */
    def balance(chars: List[Char]): Boolean = {

      def num (x: Char): Int = x match {
        case ')' => 1
        case '(' => -1
        case _ => 0
      }

      def sum(n: List[Int]): Int = {
        val tmp = if (n.isEmpty) 0 else n.head + sum (n.tail)
        if (tmp < 0) tmp-1 else tmp
      }

      (sum(chars.map (x => num(x))) == 0)
    }