Scala - week 1

Main.scala

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()
    }
  }

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

  /**
   * Exercise 2
   */
  def balance(chars: List[Char]): Boolean = {
        val open: Char = '('
        val close: Char = ')'
        def isOpen(ch: Char): Boolean = (ch == open)
        def isClose(ch: Char): Boolean = (ch == close)
        def isMatch(openChar: Char, closeChar: Char): Boolean = (isOpen(openChar) && isClose(closeChar))
        def isBalanced(inp: List[Char], stack: String): Boolean =
            if (inp.isEmpty) stack.isEmpty
            else if (isOpen(inp.head)) isBalanced(inp.tail, stack + inp.head)
            else if (isClose(inp.head))
                (!stack.isEmpty &&
                    isMatch(stack.charAt(0), inp.head) &&
                    isBalanced(inp.tail, stack.substring(1)))
            else isBalanced(inp.tail, stack)
        isBalanced(chars, "")
    }

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