gistfile1.scala

  def func(arr: Array[Int],
           leftSum: Int = 0, rightSum: Int = 0,
           leftInx: Int = -1, rightIdx: Int = -1): Int = {

    if (leftInx > rightIdx) {
      if (leftSum == rightSum) leftInx else -1
    } else {
      func(arr.slice(leftInx, rightIdx), arr.head + leftSum, arr.last + rightSum, leftInx + 1, rightIdx - 1)
    }
  }
  
  func(Array(1, 3, 8, 7, 2))