Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

Using the Template Method Pattern for DFS
The DFS class is based on the template method pattern (see Section 7.3.7), which
describes a generic computation mechanism that can be specialized by redefining
certain steps. The way we identify vertices and edges that have already been
visited during the traversal is in calls to methods isVisited, visit, and
unVisit. For us to do anything interesting, we must extend DFS and redefine
some of its auxiliary methods. This approach conforms to the template method
pattern. In Code Fragments 13.6 through 13.9, we illustrate some applications of
DFS traversal.
Class ConnectivityDFS (Code Fragment 13.6) tests whether the graph is
connected. It counts the vertices reachable by a DFS traversal starting at a vertex
and compares this number with the total number of vertices of the graph.
Code Fragment 13.6: Specialization of class DFS to
test if a graph is connected.
Class ComponentsDFS (Code Fragment 13.7) finds the connected components
of a graph. It labels each vertex with its connected component number, using the
decorator pattern, and returns the number of connected components found.
Code Fragment 13.7: Specialization of DFS to
compute connected components.
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