baekjoon - 10845

from collections import deque import sys deq = deque() for _ in range(int(sys.stdin.readline().strip())):     cmd = list(sys.stdin.readline().rstrip().split())     if cmd[0] == "push":         deq.append(cmd[1])     elif cmd[0] == "pop":         if deq:             print(deq.popleft())         else:             print(-1)     elif cmd[0] == "size":         print(len(deq))     elif cmd[0] == "empty":         if deq:             print(0)         else:             print(1)     elif cmd[0] == "front":         if deq:             print(deq[0])         else:             print(-1)     elif cmd[0] == "back":         if deq:             print(deq[-1])         else:             print(-1)

나는 deque를 사용해서 queue를 구현해주었다.