841 - Keys and Rooms.

Medium

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.