뉴스 클러스터링 (문자열 리스트 합집합, 교집합, 중복 허용 다중집합)

from collections import Counter

def solution(str1, str2):
    answer = 0
    str1,str2=str1.upper(), str2.upper()
    
    a=[]
    for i in range(1,len(str1)):
        if str1[i-1].isalpha() and str1[i].isalpha():
            a.append(str1[i-1]+str1[i])
                
    b=[]
    for i in range(1,len(str2)):
        if str2[i-1].isalpha() and str2[i].isalpha():
            b.append(str2[i-1]+str2[i])

    if len(a)==len(b)==0:
        return 65536
    
    a = Counter(a)
    b = Counter(b)
    
    c = list((a&b).elements())
    u = list((a|b).elements())

    return int(len(c)/len(u)*65536)