from queue import Queue n = int(input()) rooms = [] for _ in range(n): portals = set(map(int, input().split(','))) rooms.append(portals) a, b = map(int, input().split(',')) def bfs(start, target): visited = set() q = Queue() q.put((start, 0)) visited.add(start) while not q.empty(): room, steps = q.get() if room == target: return steps for neighbor_room, portals in enumerate(rooms): if neighbor_room not in visited and portals & rooms[room]: visited.add(neighbor_room) q.put((neighbor_room, steps + 1)) return -1 print(bfs(a-1, b-1))请给以上代码做注释

from queue import Queue  # 导入队列模块
n = int(input())  # 输入房间数
rooms = []  # 初始化房间列表
for _ in range(n):
    portals = set(map(int, input().split(',')))  # 输入每个房间的传送门集合
    rooms.append(portals)  # 将传送门集合加入房间列表中
a, b = map(int, input().split(','))  # 输入起始房间和目标房间

def bfs(start, target):
    visited = set()  # 初始化已访问的房间集合
    q = Queue()  # 初始化队列
    q.put((start, 0))  # 将起始房间和步数加入队列
    visited.add(start)  # 将起始房间加入已访问的房间集合
    while not q.empty():  # 队列非空
        room, steps = q.get()  # 弹出队头元素，即当前房间和步数
        if room == target:  # 如果当前房间是目标房间，返回步数
            return steps
        for neighbor_room, portals in enumerate(rooms):  # 遍历所有房间，找到当前房间相邻的房间
            if neighbor_room not in visited and portals & rooms[room]:  # 如果相邻房间未访问且有传送门与当前房间相连
                visited.add(neighbor_room)  # 将相邻房间添加到已访问的房间集合中
                q.put((neighbor_room, steps + 1))  # 将相邻房间和步数加入队列
    return -1  # 如果无法到达目标房间，返回 -1

print(bfs(a-1, b-1))  # 输出起始房间到目标房间的步数