def solution(records): users = {} cmd = {"Enter": "님이 들어왔습니다.", "Leave": "님이 나갔습니다."} for record in records: strSplit = record.split() if strSplit[0] == 'Enter': users[strSplit[1]] = strSplit[2] elif strSplit[0] == 'Change': users[strSplit[1]] = strSplit[2] output = [] for record in records: strSplit = record.split() if strSplit[0] != "Change": output.append('{}{}'.format(users[strSplit[1]], cmd..