Gfrktyl

Question
Alphabets are assigned numbers like -

a = 1

b = 2

c = 3

.

.

z = 26

Given a number like 1234 as input calculate count of possible different combination of character out of this string.

Example

input "123" 

output = 3 {(1,2,3), (12, 3),(1,23) }



input = "0123"

output = 0 // as 0 is not a valid number for this case a = 1 



input = ""

output = 1

Please review this scala code for this problem -

import scala.language.postfixOps

import scala.collection.mutable.HashMap



object Decode extends App {

  def validTwoDigit(number: Int) : Boolean = (9 < number) && (27 > number)

  def countMessage(message: String, lookup: HashMap[String, Int]): Int = {

    if (message.isEmpty) 1

    else if (message.head == '0') 0

    else if (lookup contains message) lookup(message)

    else {

      val count = countMessage(message.drop(1), lookup) +

                  ( if (validTwoDigit(message.take(2).toInt)) countMessage(message.drop(2), lookup) else 0 )

      lookup += (message -> count)

      count

    }

  }

  val message = args(0)

  println(message)

  println(countMessage(message, HashMap[String, Int]()))

}