List of Integers to Int (Add for odd, multiply for even)

Problem statement —
* Read the elements a and b from the given stream or array
* Perform multiplication if the index is even. (a*b) for even
* For odd perform addition. (a+b) for odd

eg. Input (6,4,1,9,2) => output 38

Using scala, with foldleft, match case, and tail recusrion 

package playground

import scala.annotation.tailrec

object Exercise extends App {
  /**
   * Read the elements a and b from the given stream or array
   * Perform multiplication if the index is even. (a*b) for even
   * For odd perform addition. (a+b) for odd
   *
   * eg Input (6,4,1,9,2) => output 38
   * */

  val arrayInt: Array[Int] = Array(6, 4, 1, 9, 2)


  //using foldLeft
  def logicImplementation(inputNumbers: Array[Int]): Int = {
    //considering true = odd false = even
    inputNumbers.foldLeft((1, false)) { (a, b) =>
      /*val ret = a._2 match { // This is another way
        case Some(x1) => if (x1) Tuple2(a._1 + b, Some(false)) else Tuple2(a._1 * b, Some(true))
        case None => Tuple2(a._1 * b, Some(true))
      }*/

      println(s"($a, $b)")
      if (a._2) Tuple2(a._1 + b, false) else Tuple2(a._1 * b, true)

      //ret
    }._1
  }

  println(logicImplementation(arrayInt))

  //Using tail recursion
  @tailrec
  def logicWithTailRec(inputNumbers: Array[Int], isEven: Boolean = false): Int = {
    val operation: (Int, Int, Boolean) => Tuple2[Int, Boolean] =
      (a, b , condition) => if (condition) Tuple2(a * b, false) else Tuple2(a + b, true)

    val res = operation(inputNumbers(0), inputNumbers(1), isEven)

    if (inputNumbers.size == 2) {
      res._1
    } else {
      logicWithTailRec(res._1 +: inputNumbers.slice(2, inputNumbers.size), res._2)
    }
  }

  println(logicWithTailRec(arrayInt))
}