ex1 scala course

gistfile1.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 == 0 || c == 0 || r == c) 1 else 
    	pascal(c, r-1) + pascal(c-1, r-1)
  }

  /**
   * Exercise 2
   */
  def balance(chars: List[Char]): Boolean = {  
    def inner_balance(count: Int, chars: List[Char]): Boolean = {
      def charValue(c: Char): Int = {
        c match {
          case '(' => 1
          case ')' => -1
          case _ => 0
        }
      }    
      count match {
        case c if c < 0 => false
        case _ if chars.isEmpty => count == 0
        case _ => inner_balance(count + charValue(chars.head), chars.tail)    
      }	        
    }
    inner_balance(0, chars)
  }

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