[Algorithm] BFS

Classical BFS Code is like: 

1  procedure BFS(G,v):
2      create a queue Q
3      enqueue v onto Q
4      mark v
5      while Q is not empty:
6          t ← Q.dequeue()
7          if t is what we are looking for:
8              return t
9          for all edges e in G.adjacentEdges(t) do
12             u ← G.adjacentVertex(t,e)
13             if u is not marked:
14                  mark u
15                  enqueue u onto Q
16     return none