42746.kt

class Solution {
    fun solution(numbers: IntArray): String {

        val sorted = numbers.sortedWith(Comparator { o1, o2 -> compare1(o1, o2) })

        if (sorted.stream().allMatch { it == 0 }){
            return "0"
        }

        return sorted.joinToString("")
    }

    private fun compare1(o1: Int, o2: Int): Int {

        var s1 = o1.toString()
        var s2 = o2.toString()

        if (s1.length == s2.length) {
            return o2 - o1
        }

        var s1First : Int = "$s1$s2".toInt()
        var s2First : Int = "$s2$s1".toInt()

        return s2First - s1First
    }
}

fun main() {
    println(Solution().solution(intArrayOf(0, 0))) // 0
    println(Solution().solution(intArrayOf(0, 1000, 0, 0))) // 100000
    println(Solution().solution(intArrayOf(12, 121))) // 12121
    println(Solution().solution(intArrayOf(21, 212))) // 21221
}