public:

bool canVisitAllRooms(vector<vector<int>>& rooms) {

int size = rooms.size();

vector<int> opened(size, 0);

int opencount = 1;

opened[0] = 1;

stack<int> keys;

keys.push(0);

while (keys.size() > 0) {

int key = keys.top();

keys.pop();

vector<int>& roomkeys = rooms[key];

for (vector<int>::const_iterator it = roomkeys.begin(); it != roomkeys.end(); ++it) {

int key = *it;

if (!opened[key]) {

opened[key] = 1;

printf("open %d\n", key);

opencount++;

if (opencount == size) return true;

keys.push(key);

}

}

}

return opencount == size;

}