Sample CP Problem with Kotlin

main.kt

val rectangleRaw = """
    KOTE
    NULE
    AFIN
"""

val dictionaryRaw = "Kotlin, fun, file, line, null"
val directions = listOf(1 to 0, 0 to -1, 0 to 1, -1 to 0)

fun main() {
    val rectangle = rectangleRaw.trimIndent().split("\n")
	val dictionary = dictionaryRaw.toUpperCase().split(", ").toHashSet()
    val prefixes = dictionary.flatMap { word ->
        println("word = ${word}")
        List(word.length + 1) { it ->
            println("[word] it = ${it}")
            val taken = word.take(it)
            println("[word] taken = ${taken.toString()}")
            taken
        }
    }.toHashSet()
    fun search(x: Int, y: Int, word: String) {
        if (word !in prefixes) {
            return
        }
        if (word in dictionary) {
            println(word)
        }
        for ((dx, dy) in directions) {
            val xNew = x + dx
            val yNew = y + dy
            val letter = rectangle.getOrNull(xNew)?.getOrNull(yNew) ?: continue
            search(xNew, yNew, word + letter)
        }
    }
    for(x in rectangle.indices) {
        for(y in rectangle[0].indices) {
            search(x, y, rectangle[x][y].toString())
        }
    }
}