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This problem is a continuation of a code kata in Python . I'm learning Scala and would like feedback on more efficient, cleaner, and functional ways of solving (and unit testing) this problem.

This problem is a continuation of a code kata in Python . I'm learning Scala and would like feedback on more efficient, cleaner, and functional ways of solving (and unit testing) this problem.

class SumToZeroNotFound(msg:String=null, cause:Throwable=null)
 extends java.lang.Exception (msg, cause) {}
trait SumToZero{
 @throws(classOf[SumToZeroNotFound])
 def process(arr: Array[Int], size: Int = 3): Array[Int]
}
object SumToZeroBruteForce extends SumToZero{
 //brute force process any size combination
 override def process(arr: Array[Int], size: Int = 3): Array[Int] = {
 arr.combinations(size).find(_.sum == 0).getOrElse(throw new SumToZeroNotFound)
 }
}
object SumToZeroBinSearch extends SumToZero{
 //optimized with sorting and binary search
 //scala does not seem to have a native binary search routine
 implicit private class Search(val arr: Array[Int]){
 def binSearch(target: Int) = {
 java.util.Arrays.binarySearch(arr.asInstanceOf[Array[Int]], target)
 }
 }
 @throws(classOf[IllegalArgumentException])
 override def process(arr: Array[Int], size: Int = 3): Array[Int] = size match {
 case 3 =>
 val sorted_arr = arr.sortWith(_<_)
 val max_len = sorted_arr.length
 for((i_val, i) <- sorted_arr.takeWhile(_ <= 0).zipWithIndex ){
 val maxj = sorted_arr(max_len - 1) - i_val
 for(j_val <- sorted_arr.slice(i+1, max_len).takeWhile(_ <= maxj)){
 val temp_sum = i_val + j_val
 val res_idx = sorted_arr.binSearch(-temp_sum)
 if (res_idx > -1) {
 return Array(i_val, j_val, sorted_arr(res_idx))
 }
 }
 }
 throw new SumToZeroNotFound
 case _ => throw new IllegalArgumentException("only support size of three for now")
 }
 private def validateSize(size: Int) = {
 if(size > 3) throw new Exception("only accepts size of 3 for now")
 }
}
object SumToZero{
 def apply(impl: String) = impl match{
 case "with_bin_search" => SumToZeroBinSearch
 case _ => SumToZeroBruteForce
 }
}

class SumToZeroNotFound(msg:String=null, cause:Throwable=null)
 extends java.lang.Exception (msg, cause) {}
trait SumToZero{
 @throws(classOf[SumToZeroNotFound])
 def process(arr: Array[Int], size: Int = 3): Array[Int]
}
object SumToZeroBruteForce extends SumToZero{
 //brute force process any size combination
 override def process(arr: Array[Int], size: Int = 3): Array[Int] = {
 arr.combinations(size).find(_.sum == 0).getOrElse(throw new SumToZeroNotFound)
 }
}
object SumToZeroBinSearch extends SumToZero{
 //optimized with sorting and binary search
 //scala does not seem to have a native binary search routine
 implicit private class Search(val arr: Array[Int]){
 def binSearch(target: Int) = {
 java.util.Arrays.binarySearch(arr.asInstanceOf[Array[Int]], target)
 }
 }
 @throws(classOf[IllegalArgumentException])
 override def process(arr: Array[Int], size: Int = 3): Array[Int] = size match {
 case 3 =>
 val sorted_arr = arr.sortWith(_<_)
 val max_len = sorted_arr.length
 for((i_val, i) <- sorted_arr.takeWhile(_ <= 0).zipWithIndex ){
 val maxj = sorted_arr(max_len - 1) - i_val
 for(j_val <- sorted_arr.slice(i+1, max_len).takeWhile(_ <= maxj)){
 val temp_sum = i_val + j_val
 val res_idx = sorted_arr.binSearch(-temp_sum)
 if (res_idx > -1) {
 return Array(i_val, j_val, sorted_arr(res_idx))
 }
 }
 }
 throw new SumToZeroNotFound
 case _ => throw new IllegalArgumentException("only support size of three for now")
 }
}
object SumToZero{
 def apply(impl: String) = impl match{
 case "with_bin_search" => SumToZeroBinSearch
 case _ => SumToZeroBruteForce
 }
}