[Programmers] Lv1: 완주하지 못한 선수(42576)

문제

- 링크: https://school.programmers.co.kr/learn/courses/30/lessons/42576

 

풀이

import java.util.HashMap;

public class Solution {

    public String solution(String[] participant, String[] completion) {
        HashMap<String, Integer> hashMap = new HashMap<>();
        for (String string : completion) {
            hashMap.put(string, hashMap.getOrDefault(string, 0) + 1);
        }

        for (String string : participant) {
            if (hashMap.getOrDefault(string, 0) == 0) {
                return string;
            }
            hashMap.put(string, hashMap.get(string) - 1);
        }

        return null;
    }

}