kotlin-koan.kt

fun main(args: Array<String>) {

    // Starte mit "rats live on arona no evil star"
    val sentence = "rats live on arona no evil star"

    // 1. change all letters with their counterparts in the alphabet
    val alphabetCounterparts: String = sentence.split(' ').map { word -> word.map { ch -> (122 - (ch.toInt() - 97)).toChar().toLowerCase() }.joinToString("") }.joinToString(" ")

    // 2. convert all letters to their numeric value in the alphabet (a = 1)
    val lettersToNumericValues:List<List<Int>> = alphabetCounterparts.split(' ').map { word -> word.map { ch -> ch.toInt() - 96 } }

    // 3. add 1 to each number, repeat this step until the largest number is 99
    val incrementedUntilOneIs99: List<List<Int>> = lettersToNumericValues.map { numberWord -> numberWord.map { it + (99 - (lettersToNumericValues.map { it.max() ?: 0 }.max() ?: 0)) } }

    // 4. reverse the phrase but keep the order in the individual numbers
    val reversed: List<List<Int>> = incrementedUntilOneIs99.reversed()

    // 5. replace all numbers with their difference with 100
    val substractedFrom100: List<List<Int>> = reversed.map { numberWord -> numberWord.map { 100 - it } }

    // 6. convert all numbers to letters
    val mappedBackToCharacters = substractedFrom100.map { numberWord -> numberWord.map { (it + 96).toChar() }.joinToString("") }.joinToString(" ")

    System.out.println(mappedBackToCharacters)
}