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    vector<int> bfsOfGraph(int V, vector<int> adj[]) {
        queue<int> q;
        q.push(0);
        vector<int> bfsVec;
         // true for a node if its in either visited or explored state.
        bool visited[V] = {false};
        visited[0] = true; // Explored.
        
        while (!q.empty()) {
            int levelSz = q.size();
            for (int i = 0; i < levelSz; i++) {
                // now here visited[node] implicitly mean its in visited state.
                int node = q.front();
                q.pop();
                bfsVec.push_back(node);
                
                for (int j = 0; j < adj[node].size(); j++) {
                    int connectedNode = adj[node][j];
                    if (!visited[connectedNode]) {
                        // mark as true to represent the node is in explored state
                        // and when in next level traversal it will be picked up, we
                        // can implicitly consider this true value to mean
                        // that time, that the node is in visited state.
                        visited[connectedNode] = true;
                        q.push(connectedNode);
                    }
                }
            }
        }
        
        return bfsVec;
    }