//DFS solution
//Time: O(n), 4ms
//Space: O(n)
class Solution {
    public boolean canVisitAllRooms(List<List<Integer>> rooms) {
        int[] visited = new int[rooms.size()];
        DFS(rooms, visited, 0);
        for(int i : visited) {
            if(i == 0) return false;
        }
        return true;
    }

    private void DFS(List<List<Integer>> rooms, int[] visited, int room) {
        if(visited[room] == 1) return;
        visited[room] = 1;
        for(int key : rooms.get(room)) {
            DFS(rooms, visited, key);
        }
    }
}