MissingNumber.scala

object MissingNumber extends App {

  def missingNumber(nums: Array[Int]): Int = {
    val found = new Array[Int](nums.length)

    for (n <- nums) {
      if (n < nums.length) found(n) = 1
    }

    val missing = found.indexOf(0)
    if (missing == -1) nums.length else missing
  }


  println(missingNumber(Array(3, 0, 1)))
  println(missingNumber(Array(0, 1)))
  println(missingNumber(Array(9, 6, 4, 2, 3, 5, 7, 0, 1)))
  println(missingNumber(Array(8, 6, 4, 2, 3, 5, 7, 0, 1)))
}