package recfun

object Main {
  def main(args: Array[String]) {
    println("Pascal's Triangle")
    for (row <- 0 to 10) {
      for (col <- 0 to row)
        print(pascal(col, row) + " ")
      println()
    }
  }

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

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

      def isOpen(char: Char): Boolean =
        char == '('

      def isClose(char: Char): Boolean =
        char == ')'

      def balanceIter(_chars: List[Char], acc: Int): Boolean =
        if (_chars.isEmpty) acc == 0
        else if (acc < 0) false
        else if (isOpen(_chars.head)) balanceIter(_chars.tail, acc + 1)
        else if (isClose(_chars.head)) balanceIter(_chars.tail, acc - 1)
        else balanceIter(_chars.tail, acc)

      balanceIter(chars, 0)
    }

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