[프로그래머스] 완주하지 못한 선수

import java.util.*;

class Solution {
    public String solution(String[] participant, String[] completion) {
        String answer = "";
        
        HashMap<String, Integer> hm = new HashMap<>();
        
        for (String str : completion) {
            if (hm.containsKey(str)) {
                hm.put(str, hm.get(str) + 1);
            } else {
                hm.put(str, 1);
            }
        }
        
        for (String str : participant) {
            if (hm.containsKey(str)) {
                if (hm.get(str) > 0) {
                    hm.put(str, hm.get(str) - 1);
                } else {
                    answer = str;
                    break;
                }
            }
            else {
                answer = str;
                break;
            }
        }
        return answer;
    }
}