def solution(phone_book): answer = True stack=[] index=0 len_pb=len(phone_book) while index!=len_pb: stack=phone_book.pop() len_st=len(stack) for num in phone_book: len_num=len(num) if len_st>len_num: if num==stack[:len_num]: return False else: if num[:len_st]==stack: return False index+=1 return answer 쉽게 끝냈다