프로그래머스 - 코딩테스트 연습 - 해시 - 완주하지 못한 선수

문제

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

풀이

from collections import defaultdict


def solution(participant, completion):
    completes = defaultdict(int)
    for name in completion:
        completes[name] += 1

    for name in participant:
        if name in completes and completes[name] > 0:
            completes[name] -= 1
        else:
            return name

Collections.Counter 모듈을 이용한 풀이

import collections


def solution(participant, completion):
    answer = collections.Counter(participant) - collections.Counter(completion)
    return list(answer.keys())[0]