The.Algorithm.Design.Manual.Springer-Verlag.1998

Breadth-First Search
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Breadth-First Search
Figure: An undirected graph and its breadth-first search tree
The basic breadth-first search algorithm is given below. At some point during the traversal, every node in the graph changes
state from undiscovered to discovered. In a breadth-first search of an undirected graph, we assign a direction to each edge,
from the discoverer u to the discovered v. We thus denote u to be the parent p[v]. Since each node has exactly one parent,
except for the root, this defines a tree on the vertices of the graph. This tree, illustrated in Figure , defines a shortest path
from the root to every other node in the tree. This property makes breadth-first search very useful in shortest path problems.
BFS(G,s)
for each vertex do
state[] = ``discovered''
p[] = nil
while do
file:///E|/BOOK/BOOK2/NODE64.HTM (1 of 2) [19/1/2003 1:29:06]
state[u] = ``undiscovered''
p[u] = nil, i.e. no parent is in the BFS tree
u = dequeue[Q]
process vertex u as desired