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DfsVisit< GR, VS, TR > Class Template Reference
Algorithms » Graph Search

## Detailed Description

template<typename GR, typename VS, typename TR>
class lemon::DfsVisit< GR, VS, TR >

This class provides an efficient implementation of the DFS algorithm with visitor interface.

The DfsVisit class provides an alternative interface to the Dfs class. It works with callback mechanism, the DfsVisit object calls the member functions of the `Visitor` class on every DFS event.

This interface of the DFS algorithm should be used in special cases when extra actions have to be performed in connection with certain events of the DFS algorithm. Otherwise consider to use Dfs or dfs() instead.

Template Parameters

  GR | The type of the digraph the algorithm runs on. The default type is ListDigraph. The value of GR is not used directly by DfsVisit, it is only passed to DfsVisitDefaultTraits.
  VS | The Visitor type that is used by the algorithm. DfsVisitor<GR> is an empty visitor, which does not observe the DFS events. If you want to observe the DFS events, you should implement your own visitor class.
  TR | The traits class that defines various types used by the algorithm. By default, it is DfsVisitDefaultTraits<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 | SetReachedMap
| Named parameter for setting ReachedMap type. More...

## Public Types

typedef TR | Traits
| The traits class.
typedef Traits::Digraph | Digraph
| The type of the digraph the algorithm runs on.
typedef VS | Visitor
| The visitor type used by the algorithm.
typedef Traits::ReachedMap | ReachedMap
| The type of the map that indicates which nodes are reached.

## Public Member Functions

| DfsVisit (const Digraph &digraph, Visitor &visitor)
| Constructor.
| ~DfsVisit ()
| Destructor.
DfsVisit & | reachedMap (ReachedMap &m)
| Sets the map that indicates which nodes are reached.
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 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.
void | init ()
| Initializes the internal data structures.
void | addSource (Node s)
| Adds a new source node.
Arc | processNextArc ()
| Processes the next arc.
Arc | 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<typename AM>
Arc | start (const AM &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.
bool | reached (Node v) const
| Checks if the given node is reached from the root(s).

## Constructor & Destructor Documentation

## DfsVisit()

template<typename GR, typename VS, typename TR>

DfsVisit | ( | const Digraph & | digraph,
|  | Visitor & | visitor )

inline

Constructor.

Parameters

  digraph | The digraph the algorithm runs on.
  visitor | The visitor object of the algorithm.

## Member Function Documentation

## reachedMap()

template<typename GR, typename VS, typename TR>

DfsVisit & 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)

## init()

template<typename GR, typename VS, typename TR>

void init | ( |  | ) |

inline

Initializes the internal data structures.

## addSource()

template<typename GR, typename VS, 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 VS, 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 VS, typename TR>

Arc 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 VS, typename TR>

bool emptyQueue | ( |  | ) | const

inline

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

## queueSize()

template<typename GR, typename VS, 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 VS, 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 VS, 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 VS, typename TR>
template<typename AM>

Arc start | ( | const AM & | 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 VS, 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 VS, 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 VS, 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();
  }
  }
  lemon::INVALID
  const Invalid INVALID
  Invalid iterators.
  Definition base.cc:32

## reached()

template<typename GR, typename VS, 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.