52_canVisitAllRooms.py

'''841. Keys and Rooms
There are n rooms labeled from 0 to n - 1 and all the rooms are locked except
for room 0. Your goal is to visit all the rooms. However, you cannot enter
a locked room without having its key.
When you visit a room, you may find a set of distinct keys in it. Each
key has a number on it, denoting which room it unlocks, and you can take
all of them with you to unlock the other rooms.
Given an array rooms where rooms[i] is the set of keys that you can obtain
if you visited room i, return true if you can visit all the rooms, or false otherwise.
Example 1:
Input: rooms = [[1],[2],[3],[]]
Output: true
Explanation: 
We visit room 0 and pick up key 1.
We then visit room 1 and pick up key 2.
We then visit room 2 and pick up key 3.
We then visit room 3.
Since we were able to visit every room, we return true.'''
from typing import List
class Solution:
  def canVisitAllRooms(self, rooms: List[List[int]]) -> bool:
    visit=[0]*len(rooms)
    def dfs(node):
      visit[node]=1
      for child in rooms[node]:
        if visit[child]==0:
          dfs(child)
    dfs(0)
    return all(visit)