import java.util.*; class Solution { public String solution(String[] participant, String[] completion) { Map map = new HashMap(); //참가자를 HashMap에 입력 for(String name : participant){ if( map.get(name) == null ){ map.put(name, 1); }else{ int value = map.get(name) + 1; map.put(name, value); } } //완주자는 value를 1씩 감소 for(String name : completion){ int value = map.get(name) - 1; map.put(name, value); } ..