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Bfs Class Template Reference
[Path and Flow Algorithms]

#include <lemon/bfs.h>

List of all members.


Detailed Description

template<typename GR, typename TR>
class lemon::Bfs< GR, TR >

This class provides an efficient implementation of the BFS algorithm.

Parameters:
GR The graph type the algorithm runs on. The default value is ListGraph. The value of GR is not used directly by Bfs, it is only passed to BfsDefaultTraits.
TR Traits class to set various data types used by the algorithm. The default traits class is BfsDefaultTraits<GR>. See BfsDefaultTraits for the documentation of a Bfs traits class.
Author:
Alpar Juttner
Todo:
A compare object would be nice.


Public Types

typedef TR::Graph Graph
 The type of the underlying graph.
typedef Graph::Node Node
 
typedef Graph::NodeIt NodeIt
 
typedef Graph::Edge Edge
 
typedef Graph::OutEdgeIt OutEdgeIt
 
typedef TR::PredMap PredMap
 The type of the map that stores the last edges of the shortest paths.
typedef TR::ReachedMap ReachedMap
 The type of the map indicating which nodes are reached.
typedef TR::ProcessedMap ProcessedMap
 The type of the map indicating which nodes are processed.
typedef TR::DistMap DistMap
 The type of the map that stores the dists of the nodes.

Public Member Functions

 Bfs (const Graph &_G)
 Constructor.
 ~Bfs ()
 Destructor.
BfspredMap (PredMap &m)
 Sets the map storing the predecessor edges.
BfsreachedMap (ReachedMap &m)
 Sets the map indicating the reached nodes.
BfsprocessedMap (ProcessedMap &m)
 Sets the map indicating the processed nodes.
BfsdistMap (DistMap &m)
 Sets the map storing the distances calculated by the algorithm.
Execution control
The simplest way to execute the algorithm is to use one of the member functions called run(...).
If you need more control on the execution, first you must call init(), then you can add several source nodes with addSource(). Finally start() will perform the actual path computation.

void init ()
 Initializes the internal data structures.
void addSource (Node s)
 Adds a new source node.
Node processNextNode ()
 Processes the next node.
bool emptyQueue ()
 Returns false if there are nodes to be processed in the queue.
int queueSize ()
 Returns the number of the nodes to be processed.
void start ()
 Executes the algorithm.
void start (Node dest)
 Executes the algorithm until dest is reached.
template<class NM>
void start (const NM &nm)
 Executes the algorithm until a condition is met.
void run (Node s)
 Runs BFS algorithm from node s.
int run (Node s, Node t)
 Finds the shortest path between s and t.
Query Functions
The result of the BFS algorithm can be obtained using these functions.
Before the use of these functions, either run() or start() must be called.

template<class P>
bool getPath (P &p, Node t)
 Copies the shortest path to t into p.
int dist (Node v) const
 The distance of a node from the root(s).
Edge pred (Node v) const
 Returns the 'previous edge' of the shortest path tree.
Node predNode (Node v) const
 Returns the 'previous node' of the shortest path tree.
const DistMapdistMap () const
 Returns a reference to the NodeMap of distances.
const PredMappredMap () const
 Returns a reference to the shortest path tree map.
bool reached (Node v)
 Checks if a node is reachable from the root.

Classes

class  DefDistMap
 Named parameter for setting DistMap type More...
class  DefPredMap
 Named parameter for setting PredMap type More...
class  DefProcessedMap
 Named parameter for setting ProcessedMap type More...
class  DefProcessedMapToBeDefaultMap
 Named parameter for setting the ProcessedMap type to be Graph::NodeMap<bool>. More...
class  DefReachedMap
 Named parameter for setting ReachedMap type More...
class  UninitializedParameter
 Exception for uninitialized parameters. More...


Constructor & Destructor Documentation

Bfs const Graph _G  )  [inline]
 

Parameters:
_G the graph the algorithm will run on.


Member Function Documentation

Bfs& predMap PredMap m  )  [inline]
 

Sets the map storing the predecessor edges. If you don't use this function before calling run(), it will allocate one. The destructor deallocates this automatically allocated map, of course.

Returns:
(*this)

Bfs& reachedMap ReachedMap m  )  [inline]
 

Sets the map indicating the reached nodes. If you don't use this function before calling run(), it will allocate one. The destructor deallocates this automatically allocated map, of course.

Returns:
(*this)

Bfs& processedMap ProcessedMap m  )  [inline]
 

Sets the map indicating the processed nodes. If you don't use this function before calling run(), it will allocate one. The destructor deallocates this automatically allocated map, of course.

Returns:
(*this)

Bfs& distMap DistMap m  )  [inline]
 

Sets the map storing the distances calculated by the algorithm. If you don't use this function before calling run(), it will allocate one. The destructor deallocates this automatically allocated map, of course.

Returns:
(*this)

void init  )  [inline]
 

Initializes the internal data structures.

void addSource Node  s  )  [inline]
 

Adds a new source node to the set of nodes to be processed.

Node processNextNode  )  [inline]
 

Processes the next node.

Returns:
The processed node.
Warning:
The queue must not be empty!

bool emptyQueue  )  [inline]
 

Returns false if there are nodes to be processed in the queue

int queueSize  )  [inline]
 

Returns the number of the nodes to be processed in the queue.

void start  )  [inline]
 

Executes the algorithm.

Precondition:
init() must be called and at least one node should be added with addSource() before using this function.
This method runs the BFS algorithm from the root node(s) in order to compute the shortest path to each node. The algorithm computes
  • The shortest path tree.
  • The distance of each node from the root(s).

void start Node  dest  )  [inline]
 

Executes the algorithm until dest is reached.

Precondition:
init() must be called and at least one node should be added with addSource() before using this function.
This method runs the BFS algorithm from the root node(s) in order to compute the shortest path to dest. The algorithm computes
  • The shortest path to dest.
  • The distance of dest from the root(s).

void start const NM &  nm  )  [inline]
 

Executes the algorithm until a condition is met.

Precondition:
init() must be called and at least one node should be added with addSource() before using this function.
Parameters:
nm must be a bool (or convertible) node map. The algorithm will stop when it reaches a node v with nm[v]==true.

void run Node  s  )  [inline]
 

This method runs the BFS algorithm from a root node s in order to compute the shortest path to each node. The algorithm computes

  • The shortest path tree.
  • The distance of each node from the root.

Note:
d.run(s) is just a shortcut of the following code.
         d.init();
         d.addSource(s);
         d.start();

int run Node  s,
Node  t
[inline]
 

Finds the shortest path between s and t.

Returns:
The length of the shortest s---t path if there exists one, 0 otherwise.
Note:
Apart from the return value, d.run(s) is just a shortcut of the following code.
         d.init();
         d.addSource(s);
         d.start(t);

bool getPath P &  p,
Node  t
[inline]
 

This function copies the shortest path to t into p. If t is a source itself or unreachable, then it does not alter p.

Todo:
Is it the right way to handle unreachable nodes?
Returns:
Returns true if a path to t was actually copied to p, false otherwise.
See also:
DirPath

int dist Node  v  )  const [inline]
 

Returns the distance of a node from the root(s).

Precondition:
run() must be called before using this function.
Warning:
If node v in unreachable from the root(s) the return value of this function is undefined.

Edge pred Node  v  )  const [inline]
 

For a node v it returns the 'previous edge' of the shortest path tree, i.e. it returns the last edge of a shortest path from the root(s) to v. It is INVALID if v is unreachable from the root(s) or v is a root. The shortest path tree used here is equal to the shortest path tree used in predNode().

Precondition:
Either run() or start() must be called before using this function.
Todo:
predEdge could be a better name.

Node predNode Node  v  )  const [inline]
 

For a node v it returns the 'previous node' of the shortest path tree, i.e. it returns the last but one node from a shortest path from the root(a) to /v. It is INVALID if v is unreachable from the root(s) or if v itself a root. The shortest path tree used here is equal to the shortest path tree used in pred().

Precondition:
Either run() or start() must be called before using this function.

const DistMap& distMap  )  const [inline]
 

Returns a reference to the NodeMap of distances.

Precondition:
Either run() or init() must be called before using this function.

const PredMap& predMap  )  const [inline]
 

Returns a reference to the NodeMap of the edges of the shortest path tree.

Precondition:
Either run() or init() must be called before using this function.

bool reached Node  v  )  [inline]
 

Returns true if v is reachable from the root.

Warning:
The source nodes are indicated as unreached.
Precondition:
Either run() or start() must be called before using this function.


The documentation for this class was generated from the following file:
Generated on Sat Aug 27 14:14:56 2005 for LEMON by  doxygen 1.4.4