42888.kt

class Solution {
    fun solution(record: Array<String>): Array<String> {
        var answer = mutableListOf<String>()

        var nickNameMap = mutableMapOf<String, String>()
        var history = mutableListOf<Pair<String, String>>()

        for (line in record) {

            val tokens = line.split(" ")
            when {
                tokens[0] == "Enter" -> {
                    nickNameMap[tokens[1]] = tokens[2]
                    history.add(Pair(tokens[0], tokens[1]))
                }
                tokens[0] == "Change" -> nickNameMap[tokens[1]] = tokens[2]
                else -> history.add(Pair(tokens[0], tokens[1]))
            }
        }

        for (hist in history) {
            val command = when (hist.first) {
                "Enter" -> "님이 들어왔습니다."
                "Leave" -> "님이 나갔습니다."
                else -> ""
            }

            answer.add("${nickNameMap[hist.second]}$command")
        }

        return answer.toTypedArray()
    }
}