Question

How to count the number of digits in an integer with Scala

Answer 1

object DigitCounterString {

  // Counts digits by converting the number to a string.
  // Idiomatic, clear, and safe for everyday Scala code.
  def countDigitsString(value: Int): Int = {
    val text: String = value.toString

    if (text.startsWith("-"))
      text.length - 1
    else
      text.length
  }

  def main(args: Array[String]): Unit = {
    val number: Int = -12345
    val digits: Int = countDigitsString(number)

    println(s"Number: $number")
    println(s"Digit count (String method): $digits")
  }
}


/*
run:

Number: -12345
Digit count (String method): 5

*/

 

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Answer 2

object DigitCounterLog10 {

  // Counts digits using math: floor(log10(n)) + 1
  // Zero must be handled explicitly.
  def countDigitsLog10(value: Int): Int = {
    val num: Int = math.abs(value)

    if (num == 0)
      1
    else
      math.floor(math.log10(num)).toInt + 1
  }

  def main(args: Array[String]): Unit = {
    val number: Int = 987654321
    val digits: Int = countDigitsLog10(number)

    println(s"Number: $number")
    println(s"Digit count (log10 method): $digits")
  }
}


/*
run:

Number: -12345
Digit count (String method): 5

*/

 

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