codility binary gap solution by scala

BinaryGap.scala

  def solve(n: Int): Int = {
    val input_seq =
      Integer.toBinaryString(n).zipWithIndex.filter(_._1 == '1').map(_._2)
    getGep(input_seq, input_seq.size - 1, 0)
  }

  @tailrec
  def getGep(input_seq: IndexedSeq[Int], idx: Int, gap: Int): Int = {
    if (idx == 0) {
      if (gap == 0) 0 else gap - 1
    } else {
      val now_gap = input_seq(idx) - input_seq(idx - 1)
      if (now_gap > gap) getGep(input_seq, idx - 1, now_gap)
      else getGep(input_seq, idx - 1, gap)
    }
  }