Dfs< GR, TR > Class Template Reference

Detailed Description

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

This class provides an efficient implementation of the DFS algorithm.

There is also a function-type interface for the DFS algorithm, which is convenient in the simplier cases and it can be used easier.

Template Parameters

GR	The type of the digraph the algorithm runs on. The default type is ListDigraph.
TR	The traits class that defines various types used by the algorithm. By default, it is DfsDefaultTraits<GR>. In most cases, this parameter should not be set directly, consider to use the named template parameters instead.

#include <lemon/dfs.h>

Classes
struct	SetPredMap
	Named parameter for setting More...
struct	SetDistMap
	Named parameter for setting More...
struct	SetReachedMap
	Named parameter for setting More...
struct	SetProcessedMap
	Named parameter for setting More...
struct	SetStandardProcessedMap
	Named parameter for setting More...

Public Types
typedef TR::Digraph	Digraph
	The type of the digraph the algorithm runs on.
typedef TR::PredMap	PredMap
	The type of the map that stores the predecessor arcs of the DFS paths.
typedef TR::DistMap	DistMap
	The type of the map that stores the distances of the nodes.
typedef TR::ReachedMap	ReachedMap
	The type of the map that indicates which nodes are reached.
typedef TR::ProcessedMap	ProcessedMap
	The type of the map that indicates which nodes are processed.
typedef PredMapPath< Digraph, PredMap >	Path
	The type of the paths.
typedef TR	Traits
	The traits class of the algorithm.

Public Member Functions
	Dfs (const Digraph &g)
	Constructor.
	~Dfs ()
	Destructor.
Dfs &	predMap (PredMap &m)
	Sets the map that stores the predecessor arcs.
Dfs &	reachedMap (ReachedMap &m)
	Sets the map that indicates which nodes are reached.
Dfs &	processedMap (ProcessedMap &m)
	Sets the map that indicates which nodes are processed.
Dfs &	distMap (DistMap &m)
	Sets the map that stores the distances of the nodes.
Execution Control
The simplest way to execute the DFS algorithm is to use one of the member functions called run(). If you need better control on the execution, you have to call
void	init ()
	Initializes the internal data structures.
void	addSource (Node s)
	Adds a new source node.
Arc	processNextArc ()
	Processes the next arc.
OutArcIt	nextArc () const
	Next arc to be processed.
bool	emptyQueue () const
	Returns false if there are nodes to be processed.
int	queueSize () const
	Returns the number of the nodes to be processed.
void	start ()
	Executes the algorithm.
void	start (Node t)
	Executes the algorithm until the given target node is reached.
template<class ArcBoolMap>
Arc	start (const ArcBoolMap &am)
	Executes the algorithm until a condition is met.
void	run (Node s)
	Runs the algorithm from the given source node.
bool	run (Node s, Node t)
	Finds the DFS path between s and t.
void	run ()
	Runs the algorithm to visit all nodes in the digraph.
Query Functions
The results of the DFS algorithm can be obtained using these functions. Either run() or start() should be called before using them.
Path	path (Node t) const
	The DFS path to the given node.
int	dist (Node v) const
	The distance of the given node from the root(s).
Arc	predArc (Node v) const
	Returns the 'previous arc' of the DFS tree for the given node.
Node	predNode (Node v) const
	Returns the 'previous node' of the DFS tree for the given node.
const DistMap &	distMap () const
	Returns a const reference to the node map that stores the distances of the nodes.
const PredMap &	predMap () const
	Returns a const reference to the node map that stores the predecessor arcs.
bool	reached (Node v) const
	Checks if the given node. node is reached from the root(s).

Constructor & Destructor Documentation

Dfs()

template<typename GR, typename TR>

Dfs ( const Digraph & g )

inline

Constructor.

Parameters

g	The digraph the algorithm runs on.

Member Function Documentation

predMap() [1/2]

template<typename GR, typename TR>

Dfs & predMap ( PredMap & m )

inline

Sets the map that stores the predecessor arcs. If you don't use this function before calling run() or init(), an instance will be allocated automatically. The destructor deallocates this automatically allocated map, of course.

Returns

(*this)

reachedMap()

template<typename GR, typename TR>

Dfs & reachedMap ( ReachedMap & m )

inline

Sets the map that indicates which nodes are reached. If you don't use this function before calling run() or init(), an instance will be allocated automatically. The destructor deallocates this automatically allocated map, of course.

Returns

(*this)

processedMap()

template<typename GR, typename TR>

Dfs & processedMap ( ProcessedMap & m )

inline

Sets the map that indicates which nodes are processed. If you don't use this function before calling run() or init(), an instance will be allocated automatically. The destructor deallocates this automatically allocated map, of course.

Returns

(*this)

distMap() [1/2]

template<typename GR, typename TR>

Dfs & distMap ( DistMap & m )

inline

Sets the map that stores the distances of the nodes calculated by the algorithm. If you don't use this function before calling run() or init(), an instance will be allocated automatically. The destructor deallocates this automatically allocated map, of course.

Returns

(*this)

init()

template<typename GR, typename TR>

void init ( )

inline

init() first, then you can add a source node with addSource() and perform the actual computation with start(). This procedure can be repeated if there are nodes that have not been reached.

Initializes the internal data structures.

addSource()

template<typename GR, typename TR>

void addSource ( Node s )

inline

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

Precondition

The stack must be empty. Otherwise the algorithm gives wrong results. (One of the outgoing arcs of all the source nodes except for the last one will not be visited and distances will also be wrong.)

processNextArc()

template<typename GR, typename TR>

Arc processNextArc ( )

inline

Processes the next arc.

Returns

The processed arc.

Precondition

The stack must not be empty.

nextArc()

template<typename GR, typename TR>

OutArcIt nextArc ( ) const

inline

Next arc to be processed.

Returns

The next arc to be processed or INVALID if the stack is empty.

emptyQueue()

template<typename GR, typename TR>

bool emptyQueue ( ) const

inline

Returns false if there are nodes to be processed in the queue (stack).

queueSize()

template<typename GR, typename TR>

int queueSize ( ) const

inline

Returns the number of the nodes to be processed in the queue (stack).

start() [1/3]

template<typename GR, typename TR>

void start ( )

inline

Executes the algorithm.

This method runs the DFS algorithm from the root node in order to compute the DFS path to each node.

The algorithm computes

• the DFS tree,
• the distance of each node from the root in the DFS tree.

  Precondition

  init() must be called and a root node should be added with addSource() before using this function.

  Note

  d.start() is just a shortcut of the following code.

  while ( !d.emptyQueue() ) {
    d.processNextArc();
  }

start() [2/3]

template<typename GR, typename TR>

void start ( Node t )

inline

Executes the algorithm until the given target node is reached.

This method runs the DFS algorithm from the root node in order to compute the DFS path to t.

The algorithm computes

• the DFS path to t,
• the distance of t from the root in the DFS tree.

  Precondition

  init() must be called and a root node should be added with addSource() before using this function.

start() [3/3]

template<typename GR, typename TR>

template<class ArcBoolMap>

Arc start ( const ArcBoolMap & am )

inline

Executes the algorithm until a condition is met.

This method runs the DFS algorithm from the root node until an arc a with am[a] true is found.

Parameters

am	A bool (or convertible) arc map. The algorithm will stop when it reaches an arc a with am[a] true.

Returns

The reached arc a with am[a] true or INVALID if no such arc was found.

Precondition

init() must be called and a root node should be added with addSource() before using this function.

Warning

Contrary to Bfs and Dijkstra, am is an arc map, not a node map.

run() [1/3]

template<typename GR, typename TR>

void run ( Node s )

inline

This method runs the DFS algorithm from node s in order to compute the DFS path to each node.

The algorithm computes

• the DFS tree,
• the distance of each node from the root in the DFS tree.

  Note

  d.run(s) is just a shortcut of the following code.

  d.init();
  d.addSource(s);
  d.start();

run() [2/3]

template<typename GR, typename TR>

bool run ( Node s, Node t )

inline

This method runs the DFS algorithm from node s in order to compute the DFS path to node t (it stops searching when t is processed)

Returns

true if t is reachable form s.

Note

Apart from the return value, d.run(s,t) is just a shortcut of the following code.

d.init();
d.addSource(s);
d.start(t);

run() [3/3]

template<typename GR, typename TR>

void run ( )

inline

This method runs the DFS algorithm in order to visit all nodes in the digraph.

Note

d.run() is just a shortcut of the following code.

d.init();
for (NodeIt n(digraph); n != INVALID; ++n) {
  if (!d.reached(n)) {
    d.addSource(n);
    d.start();
  }
}

path()

template<typename GR, typename TR>

Path path ( Node t ) const

inline

Returns the DFS path to the given node from the root(s).

Warning

t should be reached from the root(s).

Precondition

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

dist()

template<typename GR, typename TR>

int dist ( Node v ) const

inline

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

Warning

If node v is not reached from the root(s), then the return value of this function is undefined.

Precondition

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

predArc()

template<typename GR, typename TR>

Arc predArc ( Node v ) const

inline

This function returns the 'previous arc' of the DFS tree for the node v, i.e. it returns the last arc of a DFS path from a root to v. It is INVALID if v is not reached from the root(s) or if v is a root.

The DFS tree used here is equal to the DFS tree used in predNode() and predMap().

Precondition

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

predNode()

template<typename GR, typename TR>

Node predNode ( Node v ) const

inline

This function returns the 'previous node' of the DFS tree for the node v, i.e. it returns the last but one node of a DFS path from a root to v. It is INVALID if v is not reached from the root(s) or if v is a root.

The DFS tree used here is equal to the DFS tree used in predArc() and predMap().

Precondition

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

distMap() [2/2]

template<typename GR, typename TR>

const DistMap & distMap ( ) const

inline

Returns a const reference to the node map that stores the distances of the nodes calculated by the algorithm.

Precondition

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

predMap() [2/2]

template<typename GR, typename TR>

const PredMap & predMap ( ) const

inline

Returns a const reference to the node map that stores the predecessor arcs, which form the DFS tree (forest).

Precondition

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

reached()

template<typename GR, typename TR>

bool reached ( Node v ) const

inline

Returns true if v is reached from the root(s).

Precondition

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