릿코드 2225. Find Players With Zero or One Losses 코틀린

승자와 패자 각각 해시맵에 넣고,
승자엔 있는데 패자엔 없으면 무패배열에,
패자에서 1인것들은 1패배열에 넣어서 리턴


참고:전체배열에서 특정배열안에 있는걸 제거할땐 리스트를 쓰면 remove가 o(n)인데,hashSet같은 hash를 사용하면 o(1)임


정답

class Solution {
    fun findWinners(matches: Array<IntArray>): List<List<Int>> {
        val winnerHashMap = hashMapOf<Int, Int>()
        val loserHashMap = hashMapOf<Int, Int>()
        for (i in matches){
            winnerHashMap[i[0]]= winnerHashMap[i[0]]?.plus(1)?:1
            loserHashMap[i[1]]= loserHashMap[i[1]]?.plus(1)?:1
        }
        val perfectList= winnerHashMap.keys.toHashSet()
        for (i in loserHashMap.keys){
            perfectList.remove(i)
        }
        val oneLoseList= mutableListOf<Int>()
        for ((key,value) in loserHashMap){
            if (value==1){
                oneLoseList.add(key)
            }
        }

        println(winnerHashMap)
        println(loserHashMap)
        println(perfectList)


        return listOf<List<Int>>(perfectList.sorted(),oneLoseList.sorted())
    }
}