# 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 = [,,,[]]
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],,]
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.

### 解題

Runtime: 4 ms, faster than 91.6%
Memory Usage: 4 MB, less than 84.55%
func canVisitAllRooms(rooms [][]int) bool {
visited := make([]bool, len(rooms))
keys := make([]int, 0)
keys = append(keys, 0)
for len(keys) != 0 {
top := keys
keys = keys[1:]
visited[top] = true
for _, k := range rooms[top] {
if !visited[k] {
keys = append(keys, k)
}
}
}
for _, v := range visited {
if !v { return false }
}
return true
}