Functional cubs Kotlin

functiona_cubs.kt

object Part1 {
    fun captcha(input: String): Int =
        input.zipWithNext()
                .let { it + (input.first() to input.last()) }
                .filter { (first, second) -> first == second}
                .map { it.first }
                .map(Character::getNumericValue)
                .sum()
}

object Part2 {
    fun captcha(input: String): Int =
            input.mapIndexed { index, c -> c to input[getIndex(index, input)] }
                    .filter { (first, second) -> first == second }
                    .map { it.first }
                    .map(Character::getNumericValue)
                    .sum()

    private fun getIndex(index: Int, input: String) = (index + input.length / 2) % input.length
}