How to balance parenthesis recursively

Question

I\'m working on some code to balance parenthesis, this question proved most useful for the algorithm.

I implemented it in my first language (PHP) but I\'m learning Scala

Answer 1

Same as Aaron Novstrup's answer but using 'if else'. I'm also attending the same course but we are taught upto if/else only so far.

def balance(chars: List[Char]): Boolean = {
    def balanced(chars: List[Char], open: Int): Boolean = 
      if (chars.isEmpty) open == 0
      else if (chars.head == '(') balanced(chars.tail, open + 1)
      else if (chars.head == ')') open > 0 && balanced(chars.tail, open - 1)
      else balanced(chars.tail, open)
    balanced(chars, 0)
}