How iterator is working in this BFS traversal

#1 
  for(int nbr:l[node]){
        if(!visited[nbr]){
            q.push(nbr);
            //mark that nbr as visietd
               visited[nbr]=true;
        }
    }
#2

Hey if you are asking how exactly for(int nbr:l[node]) then this a short method provided in later versions of c++ to traverse over data containers/arrays and it also saves some time otherwise you have to write like this
for (std::vector::iterator it = v.begin(); it != v.end(); ++it)

For more details go check this : https://www.bogotobogo.com/cplusplus/C11/C11_Type_Inference_auto_range_based_for_loop.php

If this is not what you have asked then please elaborate.

#3

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