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.
Input: rooms = [,,,] 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.
Input: rooms = [[1,3],[3,0,1],,] Output: false Explanation: We can not enter room number 2 since the only key that unlocks it is in that room.
- n == rooms.length
- 2 <= n <= 1000
- 0 <= rooms[i].length <= 1000
- 1 <= sum(rooms[i].length) <= 3000
- 0 <= rooms[i][j] < n
- All the values of rooms[i] are unique.
I solved this problem like this.
If we use stack, you can solve easily.
class Solution: def canVisitAllRooms(self, rooms: List[List[int]]) -> bool: visited =  * len(rooms) visited = 1 stack = rooms while stack: next_rooms = stack.pop() if visited[next_rooms]: continue visited[next_rooms] = 1 stack.extend(rooms[next_rooms]) return sum(visited) == len(rooms)