package recfun
import common._

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()
    }
    println(pascal(100,10))
  }

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

  /**
   * Exercise 2
   */
  def balance(chars: List[Char]): Boolean = {
    def calcBalanceWithPrebalance(prebalance: Int, chars : List[Char]) : Int =
      if (chars.isEmpty)
        prebalance
      else if (prebalance < 0)
        -1
      else if (chars.head == '(')
          calcBalanceWithPrebalance(prebalance + 1, chars.tail)
      else if (chars.head == ')')
          calcBalanceWithPrebalance(prebalance - 1, chars.tail)
      else
          calcBalanceWithPrebalance(prebalance, chars.tail)
    calcBalanceWithPrebalance(0, chars) == 0
  }

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