fibonacci in scala

fibonacci-1.scala

def fibonacci (n: Int): Int = {
  @tailrec
  def fib (start: Int, prev: Int, prevPrev: Int = 0): Int = {
    start match {
      case start if (start == n) => prev
      case _ => fib(start + 1, prev + prevPrev, prev)
    }
  }
  n match {
    case _ => fib(1, 1)
  }
}

fibonacci-2.scala

def fibonacci (n: Int): Int = {
  @tailrec
  def fib (n: Int, prev: Int, sum: Int = 0): Int = {
    n match {
      case 0 => sum
      case _ => fib(n - 1, prev + sum, prev)
    }
  }
  fib(n, 1)
}

fibonacci-non-tail.scala

def fibonacci (n: Int): Int = n match {
  case 1 => 1
  case 2 => 1
  case m => fib(n-1) + fib(n-2)
}