src/lemon/bfs.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.
alpar@906
     1
/* -*- C++ -*-
alpar@921
     2
 * src/lemon/bfs.h - Part of LEMON, a generic C++ optimization library
alpar@906
     3
 *
alpar@1164
     4
 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@906
     5
 * (Egervary Combinatorial Optimization Research Group, EGRES).
alpar@906
     6
 *
alpar@906
     7
 * Permission to use, modify and distribute this software is granted
alpar@906
     8
 * provided that this copyright notice appears in all copies. For
alpar@906
     9
 * precise terms see the accompanying LICENSE file.
alpar@906
    10
 *
alpar@906
    11
 * This software is provided "AS IS" with no warranty of any kind,
alpar@906
    12
 * express or implied, and with no claim as to its suitability for any
alpar@906
    13
 * purpose.
alpar@906
    14
 *
alpar@906
    15
 */
alpar@906
    16
alpar@921
    17
#ifndef LEMON_BFS_H
alpar@921
    18
#define LEMON_BFS_H
alpar@774
    19
alpar@774
    20
///\ingroup flowalgs
alpar@774
    21
///\file
alpar@774
    22
///\brief Bfs algorithm.
alpar@774
    23
///
alpar@774
    24
///\todo Revise Manual.
alpar@774
    25
alpar@921
    26
#include <lemon/bin_heap.h>
alpar@921
    27
#include <lemon/invalid.h>
klao@977
    28
#include <lemon/graph_utils.h>
alpar@774
    29
alpar@921
    30
namespace lemon {
alpar@774
    31
alpar@774
    32
/// \addtogroup flowalgs
alpar@774
    33
/// @{
alpar@774
    34
alpar@781
    35
  ///%BFS algorithm class.
alpar@774
    36
alpar@781
    37
  ///This class provides an efficient implementation of %BFS algorithm.
alpar@781
    38
  ///\param GR The graph type the algorithm runs on.
alpar@781
    39
  ///This class does the same as Dijkstra does with constant 1 edge length,
alpar@781
    40
  ///but it is faster.
alpar@774
    41
  ///
alpar@781
    42
  ///\author Alpar Juttner
alpar@774
    43
alpar@774
    44
#ifdef DOXYGEN
alpar@774
    45
  template <typename GR>
alpar@774
    46
#else
alpar@774
    47
  template <typename GR>
alpar@774
    48
#endif
alpar@774
    49
  class Bfs{
alpar@774
    50
  public:
alpar@774
    51
    ///The type of the underlying graph.
alpar@774
    52
    typedef GR Graph;
alpar@911
    53
    ///\e
alpar@774
    54
    typedef typename Graph::Node Node;
alpar@911
    55
    ///\e
alpar@774
    56
    typedef typename Graph::NodeIt NodeIt;
alpar@911
    57
    ///\e
alpar@774
    58
    typedef typename Graph::Edge Edge;
alpar@911
    59
    ///\e
alpar@774
    60
    typedef typename Graph::OutEdgeIt OutEdgeIt;
alpar@774
    61
    
alpar@774
    62
    ///\brief The type of the map that stores the last
alpar@774
    63
    ///edges of the shortest paths.
alpar@774
    64
    typedef typename Graph::template NodeMap<Edge> PredMap;
alpar@774
    65
    ///\brief The type of the map that stores the last but one
alpar@774
    66
    ///nodes of the shortest paths.
alpar@774
    67
    typedef typename Graph::template NodeMap<Node> PredNodeMap;
alpar@774
    68
    ///The type of the map that stores the dists of the nodes.
alpar@774
    69
    typedef typename Graph::template NodeMap<int> DistMap;
alpar@774
    70
alpar@774
    71
  private:
alpar@802
    72
    /// Pointer to the underlying graph.
alpar@774
    73
    const Graph *G;
alpar@802
    74
    ///Pointer to the map of predecessors edges.
alpar@774
    75
    PredMap *predecessor;
alpar@802
    76
    ///Indicates if \ref predecessor is locally allocated (\c true) or not.
alpar@774
    77
    bool local_predecessor;
alpar@802
    78
    ///Pointer to the map of predecessors nodes.
alpar@774
    79
    PredNodeMap *pred_node;
alpar@802
    80
    ///Indicates if \ref pred_node is locally allocated (\c true) or not.
alpar@774
    81
    bool local_pred_node;
alpar@802
    82
    ///Pointer to the map of distances.
alpar@774
    83
    DistMap *distance;
alpar@802
    84
    ///Indicates if \ref distance is locally allocated (\c true) or not.
alpar@774
    85
    bool local_distance;
alpar@774
    86
alpar@802
    87
    ///The source node of the last execution.
alpar@774
    88
    Node source;
alpar@774
    89
alpar@774
    90
alpar@781
    91
    ///Initializes the maps.
alpar@774
    92
    void init_maps() 
alpar@774
    93
    {
alpar@774
    94
      if(!predecessor) {
alpar@774
    95
	local_predecessor = true;
alpar@774
    96
	predecessor = new PredMap(*G);
alpar@774
    97
      }
alpar@774
    98
      if(!pred_node) {
alpar@774
    99
	local_pred_node = true;
alpar@774
   100
	pred_node = new PredNodeMap(*G);
alpar@774
   101
      }
alpar@774
   102
      if(!distance) {
alpar@774
   103
	local_distance = true;
alpar@774
   104
	distance = new DistMap(*G);
alpar@774
   105
      }
alpar@774
   106
    }
alpar@774
   107
    
alpar@774
   108
  public :    
alpar@802
   109
    ///Constructor.
alpar@802
   110
    
alpar@802
   111
    ///\param _G the graph the algorithm will run on.
alpar@911
   112
    ///
alpar@774
   113
    Bfs(const Graph& _G) :
alpar@774
   114
      G(&_G),
alpar@774
   115
      predecessor(NULL), local_predecessor(false),
alpar@774
   116
      pred_node(NULL), local_pred_node(false),
alpar@774
   117
      distance(NULL), local_distance(false)
alpar@774
   118
    { }
alpar@774
   119
    
alpar@802
   120
    ///Destructor.
alpar@774
   121
    ~Bfs() 
alpar@774
   122
    {
alpar@774
   123
      if(local_predecessor) delete predecessor;
alpar@774
   124
      if(local_pred_node) delete pred_node;
alpar@774
   125
      if(local_distance) delete distance;
alpar@774
   126
    }
alpar@774
   127
alpar@774
   128
    ///Sets the map storing the predecessor edges.
alpar@774
   129
alpar@774
   130
    ///Sets the map storing the predecessor edges.
alpar@774
   131
    ///If you don't use this function before calling \ref run(),
alpar@774
   132
    ///it will allocate one. The destuctor deallocates this
alpar@774
   133
    ///automatically allocated map, of course.
alpar@774
   134
    ///\return <tt> (*this) </tt>
alpar@774
   135
    Bfs &setPredMap(PredMap &m) 
alpar@774
   136
    {
alpar@774
   137
      if(local_predecessor) {
alpar@774
   138
	delete predecessor;
alpar@774
   139
	local_predecessor=false;
alpar@774
   140
      }
alpar@774
   141
      predecessor = &m;
alpar@774
   142
      return *this;
alpar@774
   143
    }
alpar@774
   144
alpar@774
   145
    ///Sets the map storing the predecessor nodes.
alpar@774
   146
alpar@774
   147
    ///Sets the map storing the predecessor nodes.
alpar@774
   148
    ///If you don't use this function before calling \ref run(),
alpar@774
   149
    ///it will allocate one. The destuctor deallocates this
alpar@774
   150
    ///automatically allocated map, of course.
alpar@774
   151
    ///\return <tt> (*this) </tt>
alpar@774
   152
    Bfs &setPredNodeMap(PredNodeMap &m) 
alpar@774
   153
    {
alpar@774
   154
      if(local_pred_node) {
alpar@774
   155
	delete pred_node;
alpar@774
   156
	local_pred_node=false;
alpar@774
   157
      }
alpar@774
   158
      pred_node = &m;
alpar@774
   159
      return *this;
alpar@774
   160
    }
alpar@774
   161
alpar@774
   162
    ///Sets the map storing the distances calculated by the algorithm.
alpar@774
   163
alpar@774
   164
    ///Sets the map storing the distances calculated by the algorithm.
alpar@774
   165
    ///If you don't use this function before calling \ref run(),
alpar@774
   166
    ///it will allocate one. The destuctor deallocates this
alpar@774
   167
    ///automatically allocated map, of course.
alpar@774
   168
    ///\return <tt> (*this) </tt>
alpar@774
   169
    Bfs &setDistMap(DistMap &m) 
alpar@774
   170
    {
alpar@774
   171
      if(local_distance) {
alpar@774
   172
	delete distance;
alpar@774
   173
	local_distance=false;
alpar@774
   174
      }
alpar@774
   175
      distance = &m;
alpar@774
   176
      return *this;
alpar@774
   177
    }
alpar@774
   178
    
alpar@774
   179
  ///Runs %BFS algorithm from node \c s.
alpar@774
   180
alpar@774
   181
  ///This method runs the %BFS algorithm from a root node \c s
alpar@774
   182
  ///in order to
alpar@781
   183
  ///compute a
alpar@774
   184
  ///shortest path to each node. The algorithm computes
alpar@781
   185
  ///- The %BFS tree.
alpar@774
   186
  ///- The distance of each node from the root.
alpar@774
   187
 
alpar@774
   188
    void run(Node s) {
alpar@774
   189
      
alpar@774
   190
      init_maps();
alpar@774
   191
      
alpar@774
   192
      source = s;
alpar@774
   193
      
alpar@774
   194
      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
alpar@774
   195
	predecessor->set(u,INVALID);
alpar@774
   196
	pred_node->set(u,INVALID);
alpar@774
   197
      }
alpar@774
   198
      
klao@946
   199
      int N = countNodes(*G);
alpar@774
   200
      std::vector<typename Graph::Node> Q(N);
alpar@774
   201
      int Qh=0;
alpar@774
   202
      int Qt=0;
alpar@774
   203
      
alpar@774
   204
      Q[Qh++]=source;
alpar@774
   205
      distance->set(s, 0);
alpar@774
   206
      do {
alpar@774
   207
	Node m;
alpar@774
   208
	Node n=Q[Qt++];
alpar@774
   209
	int d= (*distance)[n]+1;
alpar@774
   210
	
alpar@774
   211
	for(OutEdgeIt e(*G,n);e!=INVALID;++e)
alpar@986
   212
	  if((m=G->target(e))!=s && (*predecessor)[m]==INVALID) {
alpar@774
   213
	    Q[Qh++]=m;
alpar@774
   214
	    predecessor->set(m,e);
alpar@774
   215
	    pred_node->set(m,n);
alpar@774
   216
	    distance->set(m,d);
alpar@774
   217
	  }
alpar@774
   218
      } while(Qt!=Qh);
alpar@774
   219
    }
alpar@774
   220
    
alpar@774
   221
    ///The distance of a node from the root.
alpar@774
   222
alpar@774
   223
    ///Returns the distance of a node from the root.
alpar@774
   224
    ///\pre \ref run() must be called before using this function.
alpar@774
   225
    ///\warning If node \c v in unreachable from the root the return value
alpar@774
   226
    ///of this funcion is undefined.
alpar@774
   227
    int dist(Node v) const { return (*distance)[v]; }
alpar@774
   228
alpar@781
   229
    ///Returns the 'previous edge' of the %BFS path tree.
alpar@774
   230
alpar@781
   231
    ///For a node \c v it returns the 'previous edge' of the %BFS tree,
alpar@781
   232
    ///i.e. it returns the last edge of a shortest path from the root to \c
alpar@774
   233
    ///v. It is \ref INVALID
alpar@774
   234
    ///if \c v is unreachable from the root or if \c v=s. The
alpar@781
   235
    ///%BFS tree used here is equal to the %BFS tree used in
alpar@774
   236
    ///\ref predNode(Node v).  \pre \ref run() must be called before using
alpar@774
   237
    ///this function.
alpar@774
   238
    Edge pred(Node v) const { return (*predecessor)[v]; }
alpar@774
   239
alpar@781
   240
    ///Returns the 'previous node' of the %BFS tree.
alpar@774
   241
alpar@781
   242
    ///For a node \c v it returns the 'previous node' on the %BFS tree,
alpar@774
   243
    ///i.e. it returns the last but one node from a shortest path from the
alpar@774
   244
    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
alpar@781
   245
    ///\c v=s. The shortest path tree used here is equal to the %BFS
alpar@774
   246
    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
alpar@774
   247
    ///using this function.
alpar@774
   248
    Node predNode(Node v) const { return (*pred_node)[v]; }
alpar@774
   249
    
alpar@774
   250
    ///Returns a reference to the NodeMap of distances.
alpar@774
   251
    
alpar@774
   252
    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
alpar@774
   253
    ///be called before using this function.
alpar@774
   254
    const DistMap &distMap() const { return *distance;}
alpar@774
   255
 
alpar@781
   256
    ///Returns a reference to the %BFS tree map.
alpar@774
   257
alpar@774
   258
    ///Returns a reference to the NodeMap of the edges of the
alpar@781
   259
    ///%BFS tree.
alpar@774
   260
    ///\pre \ref run() must be called before using this function.
alpar@774
   261
    const PredMap &predMap() const { return *predecessor;}
alpar@774
   262
 
alpar@781
   263
    ///Returns a reference to the map of last but one nodes of shortest paths.
alpar@774
   264
alpar@781
   265
    ///Returns a reference to the NodeMap of the last but one nodes on the
alpar@781
   266
    ///%BFS tree.
alpar@774
   267
    ///\pre \ref run() must be called before using this function.
alpar@774
   268
    const PredNodeMap &predNodeMap() const { return *pred_node;}
alpar@774
   269
alpar@774
   270
    ///Checks if a node is reachable from the root.
alpar@774
   271
alpar@774
   272
    ///Returns \c true if \c v is reachable from the root.
alpar@802
   273
    ///\note The root node is reported to be reached!
alpar@774
   274
    ///
alpar@774
   275
    ///\pre \ref run() must be called before using this function.
alpar@774
   276
    ///
alpar@780
   277
    bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
alpar@774
   278
    
alpar@774
   279
  };
alpar@774
   280
  
alpar@774
   281
/// @}
alpar@774
   282
  
alpar@921
   283
} //END OF NAMESPACE LEMON
alpar@774
   284
alpar@774
   285
#endif
alpar@774
   286
alpar@774
   287