완주하지 못한 선수

Python - 예전에 푼 걸 다시 풀어보았다.

def solution(participant, completion):
    name_dict = dict()
    
    for name in participant:
        if name_dict.get(name):
            name_dict[name] += 1
        else:
            name_dict[name] = 1
    
    for name in completion:
        count = name_dict[name]
        if count == 1:
            del name_dict[name]
        else:
            name_dict[name] -= 1
    
    return list(name_dict.keys())[0]
    
    
    # 효율성 X
    # for name in completion:
    #     participant.remove(name)
    # return participant[0]