Mergesort with scala

MergeSort.scala

object MergeSort {
  def sort(source: Array[Int]): Unit = {
    branch(source, 0, source.length)
  }

  private def sortAndMerge(source: Array[Int],
                           offset0: Int, len0: Int,
                           offset1: Int, len1: Int): Unit = {

    val buffer = new Array[Int](len0 + len1)

    var idx0 = offset0
    var idx1 = offset1
    val end0 = offset0 + len0
    val end1 = offset1 + len1

    for (idx <- 0 until buffer.length) {
      if (idx0 == end0) {
        buffer(idx) = source(idx1)
        idx1 += 1
      } else if (idx1 == end1) {
        buffer(idx) = source(idx0)
        idx0 += 1
      } else if (source(idx0) < source(idx1)) {
        buffer(idx) = source(idx0)
        idx0 += 1
      } else {
        buffer(idx) = source(idx1)
        idx1 += 1
      }
    }

    for (i <- 0 until buffer.length) {
      source(offset0 + i) = buffer(i)
    }
  }

  private def branch(source: Array[Int], offset: Int, len: Int): Unit = {
    val half = len / 2
    if (half > 1) {
      branch(source, offset, half)
    }

    if (len - half > 1) {
      branch(source, offset + half, len - half)
    }

    sortAndMerge(source, offset, half, offset + half, len - half)
  }
}

object Main {
  def main(args: Array[String]) {
    def makeSource(size: Int, maxVal: Int): Array[Int] = {
      val arr = new Array[Int](size)
      for (i <- 0 until size) {
        arr(i) = Random.nextInt(maxVal)
      }
      arr
    }

    val source = makeSource(20, 50)
    source.foreach((x: Int) => print(x + " "))

    println()

    MergeSort.sort(source)
    for (elem <- source) {
      print(elem + " ")
    }
  }
}