Count Coins - KOTLIN

// Author : Saurav Kalsoor
// Count Coins - KOTLIN

import java.util.*;

var sc = Scanner(System.`in`)

class Edge(var u: Int, var v: Int)

fun main() {
    val n = sc.nextInt()
    val m = sc.nextInt()
    val coins = ArrayList<Int>()
    for (i in 0 until n) {
        coins.add(sc.nextInt())
    }
    val arr: ArrayList<Edge> = ArrayList<Edge>()
    for (i in 0 until m) {
        val u = sc.nextInt()
        val v = sc.nextInt()
        arr.add(Edge(u, v))
    }
    println(coinsCount(arr, coins, n))
}

fun coinsCount(arr: ArrayList<Edge>, coins: ArrayList<Int>, n: Int): Int {
    val tree = ArrayList<ArrayList<Int>>()
    for (i in 0 until n) tree.add(ArrayList())
    for (e in arr) {
        tree[e.u].add(e.v)
        tree[e.v].add(e.u)
    }
    val mp = HashMap<Int, Int>()
    return uniqueCount(tree, mp, coins, 0, -1)
}

fun uniqueCount(
    tree: ArrayList<ArrayList<Int>>,
    mp: HashMap<Int, Int>,
    coins: ArrayList<Int>,
    node: Int,
    parent: Int
): Int {
    var res = 0
    mp[coins[node]] = mp.getOrDefault(coins[node], 0) + 1
    for (child in tree[node]) {
        if (child == parent) continue
        res = Math.max(res, uniqueCount(tree, mp, coins, child, node))
    }
    res = Math.max(res, mp.size)
    mp[coins[node]] = mp[coins[node]]!! - 1
    if (mp[coins[node]] == 0) mp.remove(coins[node])
    return res
}