Task

Validate the check digit of an ISBN-13 code:

   Multiply every other digit by  3.
   Add these numbers and the other digits.
   Take the remainder of this number after division by  10.
   If it is  0,   the ISBN-13 check digit is correct.


Use the following codes for testing:

   978-1734314502       (good)
   978-1734314509         (bad)
   978-1788399081       (good)
   978-1788399083         (bad)


Show output here, on this page



See also

   for details:   13-digit ISBN method of validation.       (installs cookies.)


 
fun isValidISBN13(text: String): Boolean {
    val isbn = text.replace(Regex("[- ]"), "")
    return isbn.length == 13 && isbn.map { it - '0' }
        .mapIndexed { index, value -> when (index % 2) { 0 -> value else -> 3 * value } }
        .sum() % 10 == 0
}
 