Recursion scala exercises

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()
    }
    println("Parentheses Balancing")
    println(balance(":-)".toList))

    println("Counting Change")
    println(countChange(4, List(1,2,3)))
  }

  /**
   * 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 loop(chars: List[Char], acc: Int): Boolean =
      if (chars.isEmpty) {
        acc == 0
      } else {
        val h = chars.head
        val n =
          if (h == '(') acc + 1
          else if (h == ')') acc - 1
          else acc

        if (n >= 0) loop(chars.tail, n)
        else false
      }
    loop(chars, 0)
  }

  /**
   * Exercise 3
   */
  def countChange(n: Int, coins: List[Int]): Int = {
    def f(coins: List[Int], m: Int, n: Int): Int =
      if (n == 0) 1
      else if (n < 0) 0
      else if (m <= 0 && n >= 1) 0
      else f(coins, m - 1, n) + f(coins, m, n-coins(m-1))
    f(coins, coins.length, n)
  }

}