NeuroNet.kt

import java.util.*
import kotlin.collections.HashMap


fun main() {
    println(findRoute(4, 57).contentToString())
}

fun findRoute(start: Int, end: Int): IntArray {

    val allSolutions: HashMap<Int, List<Int>> = hashMapOf()

    for (multiplier in 9 downTo 2) {
        var currentNumber = end
        val path = arrayListOf(currentNumber)

        while (currentNumber > start) {
            if (currentNumber % multiplier == 0 && (currentNumber / multiplier) >= start) {
                currentNumber /= multiplier
                path.add(currentNumber)
            } else {
                currentNumber--
                path.add(currentNumber)
            }
        }
        allSolutions[path.size] = path
    }

    if (allSolutions.isEmpty()) throw EmptyStackException()
    var pathCounter = 2
    while (true) {
        allSolutions[pathCounter]?.also { return it.reversed().toIntArray() }
        pathCounter++
    }
}