Showing alternative ways for implementing binary search in Scala: iterative, recursive and functional pattern matching.

BinarySearch.scala

def binarySearchIterative(list: Array[Int], target: Int): Int = {
  var left = 0
  var right = list.length-1
  while (left<=right) {
    val mid = left + (right-left)/2
    if (list(mid)==target)
      return mid
    else if (list(mid)>target)
      right = mid-1
    else
      left = mid+1
    }
  -1
}

def binarySearchRecursive(list: Array[Int], target: Int)
                           (start: Int=0, end: Int=list.length-1): Int = {
  if (start>end) return -1
  val mid = start + (end-start+1)/2
  if (list(mid)==target)
    return mid
  else if (list(mid)>target)
    return binarySearchRecursive(list, target)(start, mid-1)
  else
    return binarySearchRecursive(list, target)(mid+1, end)
}

def binarySearchFunctional(list: Array[Int], target: Int): Int = { 		
  def bsf(list: Array[Int], target: Int, start: Int, end: Int): Int = {
    if (start>end) return -1
    val mid = start + (end-start+1)/2
    list match {
      case (arr:Array[Int]) if (arr(mid)==target) => mid
      case (arr:Array[Int]) if (arr(mid)>target) => bsf(list, target, start, mid-1)
      case (arr:Array[Int]) if (arr(mid)<target) => bsf(list, target, mid+1, end)
    }
  }		
  bsf(list, target, 0, list.length-1)
}