김준호

import java.util.HashMap; import java.util.Map; import java.util.Set; public class Solution { public String solution(String[] participant, String[] completion) { Map<String, Integer> check = new HashMap<>(); for (String s : participant) { check.put(s, check.getOrDefault(s, 0) + 1); } for (String s : completion) { check.put(s, check.get(s) - 1); } Set<String> keySet = check.keySet(); String answer = null; for (String s : keySet) { if (check.get(s) == 1) { answer = s; } } return answer; } public static void main(String[] args) { Solution s = new Solution(); String[] participant = {"leo", "kiki", "eden"}; String[] completion = {"eden", "kiki"}; System.out.println(s.solution(participant, completion)); } }