[JAVA] 프로그래머스 - 완주하지 못한 선수

import java.util.*;
class Solution {
    public String solution(String[] participant, String[] completion) {
        String answer = "";
        HashMap<String, Integer> people = new HashMap<>();
        for (String person : participant) {
            people.put(person, people.getOrDefault(person, 0) +1);
        }
        
        for (String person : completion) {
            people.put(person, people.get(person)-1);
        }
        
        for (String key : people.keySet()) {
            if (people.get(key) != 0) {
                answer = key;
                break;
            }
        }
        return answer;
    }
}