class Solution {
public:
    bool canVisitAllRooms(vector<vector<int>>& rooms) {
        int n=rooms.size();
        queue<int> q;
        vector<bool> ret(n);
        ret[0]=true;
        for(int i=0;i<rooms[0].size();i++)
        {
            if(ret[rooms[0][i]]==false)
            {
                q.push(rooms[0][i]);
            }
        }

        while(!q.empty())
        {
            int i=q.front();
            q.pop();
            int n=rooms[i].size();
            ret[i]=true;
            for(int j=0;j<n;j++)
            {
                if(ret[rooms[i][j]]==false)
                {
                    q.push(rooms[i][j]);
                }
            }
        }
        for(int i=0;i<n;i++)
        {
            if(ret[i]==false)
               return false;
        }
        return true;
    }
};