백준 1764 "듣보잡"

파이썬 코드

import sys


n, m = map(int, sys.stdin.readline().split())

listen = set()
watch = set()

for _ in range(n):
    listen.add(sys.stdin.readline().rstrip())
    
for _ in range(m):
    watch.add(sys.stdin.readline().rstrip())
    
    
listenWatch = listen - watch
listen = listen - listenWatch

ans = list(listen)
ans.sort()
print(len(ans))

for i in ans:
    print(i)