balance.scala

 def balance(chars: List[Char]): Boolean = {
    def balanceIter(chars: List[Char], count: Int) : Boolean =
      if(count < 0) false
      else if(chars.isEmpty) count == 0
      else if(chars.head == '(') balanceIter(chars.tail, count + 1)
      else if(chars.head == ')') balanceIter(chars.tail, count - 1)
      else balanceIter(chars.tail, count)

    balanceIter(chars, 0)
  }

count_change.scala

  def countChange(money: Int, coins: List[Int]): Int = {
    if(money < 0 || coins.isEmpty) 0
    else if(money == 0) 1
    else countChange(money - coins.head, coins) + countChange(money, coins.tail)
  }

pascal.scala

  def pascal(c: Int, r: Int): Int = {
    if(c == 0 || r == 0 || c == r) 1
    else pascal(c - 1, r - 1) + pascal(c, r - 1)
  }