src/lemon/dfs.h
author deba
Fri, 04 Mar 2005 17:16:01 +0000
changeset 1192 aa4483befa56
parent 986 e997802b855c
child 1218 5331168bbb18
permissions -rw-r--r--
Adding GraphEdgeSet and GraphNodeSet classes to graph_utils.h.
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/* -*- C++ -*-
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 * src/lemon/dfs.h - Part of LEMON, a generic C++ optimization library
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 *
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 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Combinatorial Optimization Research Group, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_DFS_H
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#define LEMON_DFS_H
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///\ingroup flowalgs
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///\file
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///\brief %DFS algorithm.
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///
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///\todo Revise Manual.
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#include <lemon/graph_utils.h>
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#include <lemon/invalid.h>
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namespace lemon {
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/// \addtogroup flowalgs
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/// @{
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  ///%DFS algorithm class.
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  ///This class provides an efficient implementation of %DFS algorithm.
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  ///
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  ///\param GR The graph type the algorithm runs on.
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  ///
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  ///\author Alpar Juttner
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#ifdef DOXYGEN
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  template <typename GR>
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#else
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  template <typename GR>
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#endif
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  class Dfs{
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  public:
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    ///The type of the underlying graph.
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    typedef GR Graph;
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    ///\e
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    typedef typename Graph::Node Node;
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    ///\e
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    typedef typename Graph::NodeIt NodeIt;
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    ///\e
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    typedef typename Graph::Edge Edge;
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    ///\e
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    typedef typename Graph::OutEdgeIt OutEdgeIt;
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    ///\brief The type of the map that stores the last
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    ///edges of the paths on the %DFS tree.
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    typedef typename Graph::template NodeMap<Edge> PredMap;
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    ///\brief The type of the map that stores the last but one
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    ///nodes of the paths on the %DFS tree.
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    typedef typename Graph::template NodeMap<Node> PredNodeMap;
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    ///The type of the map that stores the dists of the nodes on the %DFS tree.
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    typedef typename Graph::template NodeMap<int> DistMap;
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  private:
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    /// Pointer to the underlying graph.
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    const Graph *G;
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    ///Pointer to the map of predecessors edges.
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    PredMap *predecessor;
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    ///Indicates if \ref predecessor is locally allocated (\c true) or not.
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    bool local_predecessor;
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    ///Pointer to the map of predecessors nodes.
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    PredNodeMap *pred_node;
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    ///Indicates if \ref pred_node is locally allocated (\c true) or not.
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    bool local_pred_node;
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    ///Pointer to the map of distances.
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    DistMap *distance;
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    ///Indicates if \ref distance is locally allocated (\c true) or not.
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    bool local_distance;
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    ///The source node of the last execution.
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    Node source;
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    ///Initializes the maps.
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    void init_maps() 
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    {
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      if(!predecessor) {
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	local_predecessor = true;
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	predecessor = new PredMap(*G);
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      }
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      if(!pred_node) {
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	local_pred_node = true;
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	pred_node = new PredNodeMap(*G);
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      }
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      if(!distance) {
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	local_distance = true;
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	distance = new DistMap(*G);
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      }
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    }
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  public :    
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    ///Constructor.
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    ///\param _G the graph the algorithm will run on.
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    ///
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    Dfs(const Graph& _G) :
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      G(&_G),
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      predecessor(NULL), local_predecessor(false),
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      pred_node(NULL), local_pred_node(false),
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      distance(NULL), local_distance(false)
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    { }
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    ///Destructor.
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    ~Dfs() 
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    {
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      if(local_predecessor) delete predecessor;
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      if(local_pred_node) delete pred_node;
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      if(local_distance) delete distance;
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    }
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    ///Sets the map storing the predecessor edges.
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    ///Sets the map storing the predecessor edges.
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    ///If you don't use this function before calling \ref run(),
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    ///it will allocate one. The destuctor deallocates this
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    ///automatically allocated map, of course.
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    ///\return <tt> (*this) </tt>
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    Dfs &setPredMap(PredMap &m) 
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    {
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      if(local_predecessor) {
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	delete predecessor;
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	local_predecessor=false;
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      }
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      predecessor = &m;
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      return *this;
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    }
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    ///Sets the map storing the predecessor nodes.
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    ///Sets the map storing the predecessor nodes.
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    ///If you don't use this function before calling \ref run(),
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    ///it will allocate one. The destuctor deallocates this
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    ///automatically allocated map, of course.
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    ///\return <tt> (*this) </tt>
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    Dfs &setPredNodeMap(PredNodeMap &m) 
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    {
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      if(local_pred_node) {
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	delete pred_node;
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	local_pred_node=false;
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      }
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      pred_node = &m;
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      return *this;
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    }
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    ///Sets the map storing the distances calculated by the algorithm.
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    ///Sets the map storing the distances calculated by the algorithm.
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    ///If you don't use this function before calling \ref run(),
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    ///it will allocate one. The destuctor deallocates this
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    ///automatically allocated map, of course.
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    ///\return <tt> (*this) </tt>
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    Dfs &setDistMap(DistMap &m) 
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    {
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      if(local_distance) {
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	delete distance;
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	local_distance=false;
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      }
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      distance = &m;
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      return *this;
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    }
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  ///Runs %DFS algorithm from node \c s.
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  ///This method runs the %DFS algorithm from a root node \c s
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  ///in order to
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  ///compute 
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  ///- a %DFS tree and
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  ///- the distance of each node from the root on this tree.
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    void run(Node s) {
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      init_maps();
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      source = s;
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      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
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	predecessor->set(u,INVALID);
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	pred_node->set(u,INVALID);
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      }
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      int N = countNodes(*G);
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      std::vector<typename Graph::OutEdgeIt> Q(N);
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      int Qh=0;
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      Q[Qh] = OutEdgeIt(*G, s);
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      distance->set(s, 0);
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      Node n=s;
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      Node m;
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      OutEdgeIt e;
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      do {
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	if((e=Q[Qh])!=INVALID)
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	  if((m=G->target(e))!=s && (*predecessor)[m=G->target(e)]==INVALID) {
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	    predecessor->set(m,e);
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	    pred_node->set(m,n);
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	    Q[++Qh] = OutEdgeIt(*G, m);
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	    distance->set(m,Qh);
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	    n=m;
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	  }
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	  else ++Q[Qh];
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	else if(--Qh>=0) n=G->source(Q[Qh]);
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      } while(Qh>=0);
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    }
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    ///The distance of a node from the root on the %DFS tree.
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    ///Returns the distance of a node from the root on the %DFS tree.
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    ///\pre \ref run() must be called before using this function.
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    ///\warning If node \c v in unreachable from the root the return value
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    ///of this funcion is undefined.
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    int dist(Node v) const { return (*distance)[v]; }
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    ///Returns the 'previous edge' of the %DFS path tree.
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    ///For a node \c v it returns the last edge of the path on the %DFS tree
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    ///from the root to \c
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    ///v. It is \ref INVALID
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    ///if \c v is unreachable from the root or if \c v=s. The
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    ///%DFS tree used here is equal to the %DFS tree used in
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    ///\ref predNode(Node v).  \pre \ref run() must be called before using
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    ///this function.
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    Edge pred(Node v) const { return (*predecessor)[v]; }
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    ///Returns the 'previous node' of the %DFS tree.
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    ///For a node \c v it returns the 'previous node' on the %DFS tree,
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    ///i.e. it returns the last but one node of the path from the
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    ///root to \c /v on the %DFS tree.
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    ///It is INVALID if \c v is unreachable from the root or if
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    ///\c v=s.
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    ///\pre \ref run() must be called before
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    ///using this function.
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    Node predNode(Node v) const { return (*pred_node)[v]; }
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    ///Returns a reference to the NodeMap of distances on the %DFS tree.
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    ///Returns a reference to the NodeMap of distances on the %DFS tree.
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    ///\pre \ref run() must
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    ///be called before using this function.
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    const DistMap &distMap() const { return *distance;}
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    ///Returns a reference to the %DFS tree map.
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    ///Returns a reference to the NodeMap of the edges of the
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    ///%DFS tree.
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    ///\pre \ref run() must be called before using this function.
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    const PredMap &predMap() const { return *predecessor;}
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    ///Returns a reference to the map of last but one nodes of the %DFS tree.
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    ///Returns a reference to the NodeMap of the last but one nodes of the paths
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    ///on the
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    ///%DFS tree.
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    ///\pre \ref run() must be called before using this function.
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    const PredNodeMap &predNodeMap() const { return *pred_node;}
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    ///Checks if a node is reachable from the root.
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    ///Returns \c true if \c v is reachable from the root.
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    ///\note The root node is reported to be reached!
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    ///
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    ///\pre \ref run() must be called before using this function.
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    ///
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    bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
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  };
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/// @}
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} //END OF NAMESPACE LEMON
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#endif
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