[Python] 프로그래머스 Lv1_완주하지 못한 선수

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

프로그래머스

 

"""
입출력 예시)

participant = ["leo", "kiki", "eden"], completion = ["eden", "kiki"] -> "leo"
participant = ["marina", "josipa", "nikola", "vinko", "filipa"], completion = ["josipa", "filipa", "marina", "nikola"] -> "vinko"
participant = ["mislav", "stanko", "mislav", "ana"], completion = ["stanko", "ana", "mislav"] -> "mislav"
"""

def solution(participant, completion):
    answer = ''
    for p in participant:
      if p not in completion:
        answer = p
    return answer

 

-> 내가 푼 방법으로는 참가자 중에 동명이인이 있을 경우에 대해 처리하지 못함...

 

 

 

 

---

• 방법 1) collections.Counter() 사용

from collections import Counter

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

 

• Counter(participant), Counter(completion), list((Counter(participant) - Counter(completion)).keys())) 확인

# participant = ["mislav", "stanko", "mislav", "ana"]
# completion = ["stanko", "ana", "mislav"]

"""
Counter(participant): Counter({'mislav': 2, 'stanko': 1, 'ana': 1})

Counter(completion): Counter({'stanko': 1, 'ana': 1, 'mislav': 1})

list((Counter(participant) - Counter(completion)).keys())): ['mislav']
"""

 

• collections.Counter() 설명 참고

https://velog.io/@kimdukbae/Python-collections-%EB%AA%A8%EB%93%88%EC%9D%98-Counter

[Python] collections 모듈의 Counter

 

 

 

---

• 방법 2) hash 사용

def solution(participant, completion):
    answer = ''
    temp = 0
    dic = {}

    for p in participant:
      dic[hash(p)] = p # dic = {hash(p): 'p'}
      temp += hash(p) # temp = temp + hash(p)

    for c in completion:
      temp -= hash(c) # temp = temp - hash(c)

    answer = dic[temp]

    return answer

 

-> 동일한 'misalv'라는 이름은 participant 리스트에 있으나 completion 리스트에 있으나 같은 hash 값을 가진다는 hash의 특징 활용

 

 

• hash, dic 확인 

# participant = ["mislav", "stanko", "mislav", "ana"]
# completion = ["stanko", "ana", "mislav"]

"""
p: mislav
hash(p): -1328427996545938244
dic: {-1328427996545938244: 'mislav'}
temp: -1328427996545938244

p: stanko
hash(p): -4704244479607317033
dic: {-1328427996545938244: 'mislav', -4704244479607317033: 'stanko'}
temp: -6032672476153255277

p: mislav
hash(p): -1328427996545938244
dic: {-1328427996545938244: 'mislav', -4704244479607317033: 'stanko'}
temp: -7361100472699193521

p: ana
hash(p): -8358854611270094177
dic: {-1328427996545938244: 'mislav', -4704244479607317033: 'stanko', -8358854611270094177: 'ana'}
temp: -15719955083969287698

_____________________________________________________________________________________________________________

c: stanko
hash(c): -4704244479607317033
temp: -11015710604361970665

c: ana
hash(c): -8358854611270094177
temp: -2656855993091876488

c: mislav
hash(c): -1328427996545938244
temp: -1328427996545938244

_____________________________________________________________________________________________________________

dic: {-1328427996545938244: 'mislav', -4704244479607317033: 'stanko', -8358854611270094177: 'ana'}
"""

 

 

 

 

 

참고) 

 

https://leedakyeong.tistory.com/entry/%ED%94%84%EB%A1%9C%EA%B7%B8%EB%9E%98%EB%A8%B8%EC%8A%A4-Python-%EC%99%84%EC%A3%BC%ED%95%98%EC%A7%80-%EB%AA%BB%ED%95%9C-%EC%84%A0%EC%88%98

[프로그래머스 - Python] 완주하지 못한 선수