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

  /**
   * Exercise 2
   */
  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)
  }

  /**
   * Exercise 3
   */
  def countChange(money: Int, coins: List[Int]): Int = {
    if (money < 0 ) 0
    else if (money == 0) 1
    else if (money >= 1 && coins.size <= 0) 0
    else countChange(money, coins.tail) + countChange(money - coins.head, coins)
  }