Finding Kth Smallest - KOTLIN

//Author - Saurav Kalsoor
// Finding Kth Smallest - KOTLIN

import java.util.*
import java.lang.*

var sc: Scanner = Scanner(System.`in`)

fun main() {
    val n: Int = sc.nextInt()
    val k: Int = sc.nextInt()
    val s: String = sc.next()
    println(findingKthSmallest(n, k, s))
}

fun swap(ch: CharArray, i: Int, j: Int) {
    val temp = ch[i]
    ch[i] = ch[j]
    ch[j] = temp
}

fun findingAllRearrangements(ch: CharArray, n: Int, v: Vector<String>, itr: Int) {
    if (itr == n - 1) {
        var s: String = ""
        for (i in ch) {
            s += i
        }
        v.add(s)
        return
    }
    val hs: HashSet<Char> = HashSet<Char>()
    for (i in itr until n) {
        if (!hs.contains(ch[i])) {
            hs.add(ch[i])
            swap(ch, itr, i)
            findingAllRearrangements(ch, n, v, itr + 1)
            swap(ch, itr, i)
        }
    }
}

fun findingKthSmallest(n: Int, k: Int, s: String): String {
    val ch: CharArray = s.toCharArray()
    val v: Vector<String> = Vector<String>()
    findingAllRearrangements(ch, n, v, 0)
    Collections.sort(v)
    return if (k <= v.size) {
        v.get(k - 1)
    } else "-1"
}