Scala solution for TopCoder 'SortBooks' exercise: http://community.topcoder.com/stat?c=problem_statement&pm=4557&rd=7996 #LearningScala

SortBooks.scala

object SortBooks {
  
  val lexSeparators = Set("THE","AND","OF")    
  def isABook(s:String): Boolean = {
    val words = s.split("\\s+")
  	if (words.size > 3) true else {
  		!words.map(_.toUpperCase).toSet.intersect(lexSeparators).isEmpty
  	}
  }                                              
  
  def checkManually(field1:Array[String], field2:Array[String]):Array[Int] = {
  	val bookDef = field1.zip(field2).zipWithIndex
  	val booksToCheck = bookDef.filter({case ((field1,field2),index) => !(isABook(field1) ^ isABook(field2))})
  	booksToCheck.map({case ((field1,field2),index) => index}).toArray
  }                                           
    
  val fields1 = Array( "J R R Tolkien", "THE Jungle BOOK" )
  val fields2 = Array( "THE HOBBIT", "RUDYARD KIPLING" )

  checkManually(fields1,fields2)                  //> res0: Array[Int] = Array(0)
  
}

Nice use of xor! You can also leverage the rich API to avoid running through the whole list too many times like this:

  def isABook(s:String): Boolean = {
   val words = s.split("\\s+")
   (words.size > 3) ||
    words.find(w => lexSeparators.contains(w.toUpperCase)).isDefined
  }

  def checkManually(field1:Array[String], field2:Array[String]):Array[Int] = 
    field1.zip(field2)
      .zipWithIndex
      .collect({case ((field1,field2),index)
                    if !(isABook(field1) ^ isABook(field2)) => index})
      .toArray

I like the more compact form. Thanks!