# [Solved] 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.

Table of Contents

## Question

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.
```

Example 2:

```Input: rooms = [[1,3],[3,0,1],[2],[0]]
Output: false
Explanation: We can not enter room number 2 since the only key that unlocks it is in that room.
```

Constraints:

• `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.

## Python Solution

```class Solution:
def canVisitAllRooms(self, rooms: List[List[int]]) -> bool:
dfs = [0]
seen = set(dfs)

while dfs:
x = dfs.pop()
for i in rooms[x]:
if i not in seen:
dfs.append(i)
seen.add(i)
if len(seen)==len(rooms):return True
return False```