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vertex parent[1...p], node adl[1...p], int where[1...p], int nr

BreadthFirstSearch()
  vertex k
  for (k=1 to p) do
     where[k] = 0; parent[k] = 0
  nr = 1
  for (k = 1 to p) do
    if (where[k] = 0)
      then Visit(k); nr = nr +1

Visit(vertex k)
  node no
  ToQueue(k); where[k] = -1
  repeat
    k = FromQueue; where[k] = nr
    no = adl[k]
    while (no != null) do
      if (where[no.v] = 0)
        then ToQueue(no.v); where[no.v] = -1
        parent[no.v] = k
      no = no.next
  until QueueEmpty