Leetcode•Jun 19, 2025
Keys and Rooms
Hazrat Ali
Leetcode
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.
Solution
/**
* @param {number[][]} rooms
* @return {boolean}
*/
const canVisitAllRooms = rooms => {
const roomsToVisit = new Set();
for (let i = 0; i < rooms.length; i++) {
roomsToVisit.add(i);
}
return helper(rooms, 0, roomsToVisit);
};
const helper = (rooms, index, roomsToVisit) => {
roomsToVisit.delete(index);
if (roomsToVisit.size === 0) {
return true;
}
for (let roomIndex of rooms[index]) {
if (roomsToVisit.has(roomIndex)) {
if (helper(rooms, roomIndex, roomsToVisit)) {
return true;
}
}
}
return false;
};