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

In Code Fragments 13.4 and 13.5, we show a Java implementation of a generic
depth-first search traversal using a general class, DFS, which has a method,
execute, which takes as input the graph, a start vertex, and any auxiliary
information needed, and then initializes the graph and calls the recursive method,
dfsTraversal, which activates the DFS traversal. Our implementation
assumes that the vertices and edges are decorable positions, and it uses
decorations to tell if vertices and edges have been visited or not. The DFS class
contains the following methods to allow it to do special tasks during a DFS
traversal:
• setup(): called prior to doing the DFS traversal call to
dfsTraversal().
• initResult(): called at the beginning of the execution of
dfsTraversal().
• startVisit(v): called at the start of the visit of v.
• traverseDiscovery(e,v): called when a discovery edge e out of v is
traversed.
• traverseBack(e,v): called when a back edge e out of v is traversed.
• isDone(): called to determine whether to end the traversal early.
• finishVisit(v): called when we are finished exploring from v.
• result(): called to return the output of dfsTraversal.
• finalResult(r): called to return the output of the execute method,
given the output, r, from dfsTraversal.
Code Fragment 13.4: Instance variables and support
methods of class DFS, which performs a generic DFS
traversal. The methods visit, unVisit, and
isVisited are implemented using decorable
positions that are parameterized using the wildcard
symbol, "?", which can match either the V or the E
parameter used for decorable positions. (Continues in
Code Fragment 13.5.)
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