class Solution {
public:
    void track_back(vector<vector<int>> &rooms ,vector<int> &keys , int indnx)
    {
        if(keys[indnx] != 0 ) return;
        keys[indnx]++;
        for(int i=0 ; i<rooms[indnx].size() ; i++)
        {
            track_back(rooms,keys,rooms[indnx][i]);
        }
        return;
    }
    bool canVisitAllRooms(vector<vector<int>>& rooms) {
        vector<int> keys(rooms.size() ,0);
        track_back(rooms,keys,0);
        for(int i=0 ; i<keys.size() ;i++) 
            if(keys[i] == 0) return false;
        return true;
    }
};