The Damm algorithm is a checksum algorithm which detects all single digit errors and adjacent transposition errors.



The algorithm is named after H. Michael Damm.



Task

Verify the checksum, stored as last digit of an input.



// version 1.1.2
 
val table = arrayOf(
    intArrayOf(0, 3, 1,	7, 5, 9, 8, 6, 4, 2),
    intArrayOf(7, 0, 9, 2, 1, 5, 4, 8, 6, 3),
    intArrayOf(4, 2, 0, 6, 8, 7, 1, 3, 5, 9),
    intArrayOf(1, 7, 5, 0, 9, 8, 3, 4, 2, 6),
    intArrayOf(6, 1, 2, 3, 0, 4, 5, 9, 7, 8),
    intArrayOf(3, 6, 7, 4, 2, 0, 9, 5, 8, 1),
    intArrayOf(5, 8, 6, 9, 7, 2, 0, 1, 3, 4),
    intArrayOf(8, 9, 4, 5, 3, 6, 2, 0, 1, 7),
    intArrayOf(9, 4, 3, 8, 6, 1, 7, 2, 0, 5),
    intArrayOf(2, 5, 8, 1, 4, 3, 6, 7, 9, 0)
) 
 
fun damm(s: String): Boolean {
    var interim = 0
    for (c in s) interim = table[interim][c - '0']
    return interim == 0
}
 
fun main(args: Array<String>) {
    val numbers = intArrayOf(5724, 5727, 112946, 112949)
    for (number in numbers) {
        val isValid = damm(number.toString())
        println("${"%6d".format(number)} is ${if (isValid) "valid" else "invalid"}")
    }
}