0841. Keys and Rooms

https://leetcode.com/problems/keys-and-rooms

Description

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.

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