lemon/dimacs.h
author Akos Ladanyi <ladanyi@tmit.bme.hu>
Tue, 28 Apr 2009 16:44:48 +0100
changeset 631 d21b38647e53
parent 561 6e0525ec5355
child 877 141f9c0db4a3
permissions -rw-r--r--
Remove superfluous HAVE_CONFIG_H (#278)
alpar@385
     1
/* -*- mode: C++; indent-tabs-mode: nil; -*-
alpar@385
     2
 *
alpar@385
     3
 * This file is a part of LEMON, a generic C++ optimization library.
alpar@385
     4
 *
alpar@440
     5
 * Copyright (C) 2003-2009
alpar@385
     6
 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@385
     7
 * (Egervary Research Group on Combinatorial Optimization, EGRES).
alpar@385
     8
 *
alpar@385
     9
 * Permission to use, modify and distribute this software is granted
alpar@385
    10
 * provided that this copyright notice appears in all copies. For
alpar@385
    11
 * precise terms see the accompanying LICENSE file.
alpar@385
    12
 *
alpar@385
    13
 * This software is provided "AS IS" with no warranty of any kind,
alpar@385
    14
 * express or implied, and with no claim as to its suitability for any
alpar@385
    15
 * purpose.
alpar@385
    16
 *
alpar@385
    17
 */
alpar@385
    18
alpar@385
    19
#ifndef LEMON_DIMACS_H
alpar@385
    20
#define LEMON_DIMACS_H
alpar@385
    21
alpar@385
    22
#include <iostream>
alpar@385
    23
#include <string>
alpar@385
    24
#include <vector>
alpar@561
    25
#include <limits>
alpar@385
    26
#include <lemon/maps.h>
alpar@387
    27
#include <lemon/error.h>
alpar@385
    28
/// \ingroup dimacs_group
alpar@385
    29
/// \file
alpar@385
    30
/// \brief DIMACS file format reader.
alpar@385
    31
alpar@385
    32
namespace lemon {
alpar@385
    33
alpar@385
    34
  /// \addtogroup dimacs_group
alpar@385
    35
  /// @{
alpar@385
    36
alpar@387
    37
  /// DIMACS file type descriptor.
alpar@387
    38
  struct DimacsDescriptor
alpar@387
    39
  {
kpeter@584
    40
    ///\brief DIMACS file type enum
kpeter@584
    41
    ///
kpeter@584
    42
    ///DIMACS file type enum.
kpeter@584
    43
    enum Type {
kpeter@584
    44
      NONE,  ///< Undefined type.
kpeter@584
    45
      MIN,   ///< DIMACS file type for minimum cost flow problems.
kpeter@584
    46
      MAX,   ///< DIMACS file type for maximum flow problems.
kpeter@584
    47
      SP,    ///< DIMACS file type for shostest path problems.
kpeter@584
    48
      MAT    ///< DIMACS file type for plain graphs and matching problems.
kpeter@584
    49
    };
alpar@387
    50
    ///The file type
alpar@387
    51
    Type type;
kpeter@388
    52
    ///The number of nodes in the graph
alpar@387
    53
    int nodeNum;
kpeter@388
    54
    ///The number of edges in the graph
alpar@387
    55
    int edgeNum;
alpar@387
    56
    int lineShift;
kpeter@584
    57
    ///Constructor. It sets the type to \c NONE.
alpar@387
    58
    DimacsDescriptor() : type(NONE) {}
alpar@387
    59
  };
alpar@387
    60
alpar@387
    61
  ///Discover the type of a DIMACS file
alpar@387
    62
kpeter@584
    63
  ///This function starts seeking the beginning of the given file for the
kpeter@584
    64
  ///problem type and size info. 
kpeter@584
    65
  ///The found data is returned in a special struct that can be evaluated
kpeter@584
    66
  ///and passed to the appropriate reader function.
alpar@387
    67
  DimacsDescriptor dimacsType(std::istream& is)
alpar@387
    68
  {
alpar@387
    69
    DimacsDescriptor r;
alpar@387
    70
    std::string problem,str;
alpar@387
    71
    char c;
alpar@387
    72
    r.lineShift=0;
alpar@387
    73
    while (is >> c)
alpar@387
    74
      switch(c)
alpar@387
    75
        {
alpar@387
    76
        case 'p':
alpar@387
    77
          if(is >> problem >> r.nodeNum >> r.edgeNum)
alpar@387
    78
            {
alpar@387
    79
              getline(is, str);
alpar@387
    80
              r.lineShift++;
alpar@387
    81
              if(problem=="min") r.type=DimacsDescriptor::MIN;
alpar@387
    82
              else if(problem=="max") r.type=DimacsDescriptor::MAX;
alpar@387
    83
              else if(problem=="sp") r.type=DimacsDescriptor::SP;
alpar@387
    84
              else if(problem=="mat") r.type=DimacsDescriptor::MAT;
alpar@387
    85
              else throw FormatError("Unknown problem type");
alpar@387
    86
              return r;
alpar@387
    87
            }
alpar@387
    88
          else
alpar@387
    89
            {
alpar@387
    90
              throw FormatError("Missing or wrong problem type declaration.");
alpar@387
    91
            }
alpar@387
    92
          break;
alpar@387
    93
        case 'c':
alpar@387
    94
          getline(is, str);
alpar@387
    95
          r.lineShift++;
alpar@387
    96
          break;
alpar@387
    97
        default:
alpar@387
    98
          throw FormatError("Unknown DIMACS declaration.");
alpar@387
    99
        }
alpar@387
   100
    throw FormatError("Missing problem type declaration.");
alpar@387
   101
  }
alpar@387
   102
alpar@387
   103
kpeter@584
   104
  /// \brief DIMACS minimum cost flow reader function.
alpar@385
   105
  ///
kpeter@388
   106
  /// This function reads a minimum cost flow instance from DIMACS format,
kpeter@388
   107
  /// i.e. from a DIMACS file having a line starting with
alpar@385
   108
  /// \code
alpar@385
   109
  ///   p min
alpar@385
   110
  /// \endcode
alpar@387
   111
  /// At the beginning, \c g is cleared by \c g.clear(). The supply
alpar@561
   112
  /// amount of the nodes are written to the \c supply node map
alpar@561
   113
  /// (they are signed values). The lower bounds, capacities and costs
alpar@561
   114
  /// of the arcs are written to the \c lower, \c capacity and \c cost
alpar@561
   115
  /// arc maps.
alpar@561
   116
  ///
alpar@561
   117
  /// If the capacity of an arc is less than the lower bound, it will
alpar@561
   118
  /// be set to "infinite" instead. The actual value of "infinite" is
alpar@561
   119
  /// contolled by the \c infty parameter. If it is 0 (the default value),
alpar@561
   120
  /// \c std::numeric_limits<Capacity>::infinity() will be used if available,
alpar@561
   121
  /// \c std::numeric_limits<Capacity>::max() otherwise. If \c infty is set to
alpar@561
   122
  /// a non-zero value, that value will be used as "infinite".
alpar@387
   123
  ///
alpar@387
   124
  /// If the file type was previously evaluated by dimacsType(), then
alpar@387
   125
  /// the descriptor struct should be given by the \c dest parameter.
alpar@385
   126
  template <typename Digraph, typename LowerMap,
alpar@387
   127
            typename CapacityMap, typename CostMap,
alpar@387
   128
            typename SupplyMap>
alpar@387
   129
  void readDimacsMin(std::istream& is,
alpar@387
   130
                     Digraph &g,
alpar@387
   131
                     LowerMap& lower,
alpar@387
   132
                     CapacityMap& capacity,
alpar@387
   133
                     CostMap& cost,
alpar@387
   134
                     SupplyMap& supply,
alpar@561
   135
                     typename CapacityMap::Value infty = 0,
alpar@387
   136
                     DimacsDescriptor desc=DimacsDescriptor())
alpar@385
   137
  {
alpar@385
   138
    g.clear();
alpar@385
   139
    std::vector<typename Digraph::Node> nodes;
alpar@385
   140
    typename Digraph::Arc e;
alpar@385
   141
    std::string problem, str;
alpar@385
   142
    char c;
alpar@385
   143
    int i, j;
alpar@387
   144
    if(desc.type==DimacsDescriptor::NONE) desc=dimacsType(is);
alpar@387
   145
    if(desc.type!=DimacsDescriptor::MIN)
alpar@387
   146
      throw FormatError("Problem type mismatch");
alpar@387
   147
alpar@387
   148
    nodes.resize(desc.nodeNum + 1);
alpar@387
   149
    for (int k = 1; k <= desc.nodeNum; ++k) {
alpar@387
   150
      nodes[k] = g.addNode();
alpar@387
   151
      supply.set(nodes[k], 0);
alpar@387
   152
    }
alpar@387
   153
alpar@385
   154
    typename SupplyMap::Value sup;
alpar@385
   155
    typename CapacityMap::Value low;
alpar@385
   156
    typename CapacityMap::Value cap;
alpar@385
   157
    typename CostMap::Value co;
alpar@561
   158
    typedef typename CapacityMap::Value Capacity;
alpar@561
   159
    if(infty==0)
alpar@561
   160
      infty = std::numeric_limits<Capacity>::has_infinity ?
alpar@561
   161
        std::numeric_limits<Capacity>::infinity() :
alpar@561
   162
        std::numeric_limits<Capacity>::max();
alpar@561
   163
alpar@385
   164
    while (is >> c) {
alpar@385
   165
      switch (c) {
alpar@385
   166
      case 'c': // comment line
alpar@385
   167
        getline(is, str);
alpar@385
   168
        break;
alpar@385
   169
      case 'n': // node definition line
alpar@385
   170
        is >> i >> sup;
alpar@385
   171
        getline(is, str);
alpar@385
   172
        supply.set(nodes[i], sup);
alpar@385
   173
        break;
alpar@561
   174
      case 'a': // arc definition line
alpar@385
   175
        is >> i >> j >> low >> cap >> co;
alpar@385
   176
        getline(is, str);
alpar@385
   177
        e = g.addArc(nodes[i], nodes[j]);
alpar@385
   178
        lower.set(e, low);
alpar@561
   179
        if (cap >= low)
alpar@385
   180
          capacity.set(e, cap);
alpar@385
   181
        else
alpar@561
   182
          capacity.set(e, infty);
alpar@385
   183
        cost.set(e, co);
alpar@385
   184
        break;
alpar@385
   185
      }
alpar@385
   186
    }
alpar@385
   187
  }
alpar@385
   188
alpar@385
   189
  template<typename Digraph, typename CapacityMap>
alpar@387
   190
  void _readDimacs(std::istream& is,
alpar@387
   191
                   Digraph &g,
alpar@387
   192
                   CapacityMap& capacity,
alpar@387
   193
                   typename Digraph::Node &s,
alpar@387
   194
                   typename Digraph::Node &t,
alpar@561
   195
                   typename CapacityMap::Value infty = 0,
alpar@387
   196
                   DimacsDescriptor desc=DimacsDescriptor()) {
alpar@385
   197
    g.clear();
alpar@387
   198
    s=t=INVALID;
alpar@385
   199
    std::vector<typename Digraph::Node> nodes;
alpar@385
   200
    typename Digraph::Arc e;
alpar@385
   201
    char c, d;
alpar@385
   202
    int i, j;
alpar@385
   203
    typename CapacityMap::Value _cap;
alpar@385
   204
    std::string str;
alpar@387
   205
    nodes.resize(desc.nodeNum + 1);
alpar@387
   206
    for (int k = 1; k <= desc.nodeNum; ++k) {
alpar@387
   207
      nodes[k] = g.addNode();
alpar@387
   208
    }
alpar@561
   209
    typedef typename CapacityMap::Value Capacity;
alpar@387
   210
alpar@561
   211
    if(infty==0)
alpar@561
   212
      infty = std::numeric_limits<Capacity>::has_infinity ?
alpar@561
   213
        std::numeric_limits<Capacity>::infinity() :
alpar@561
   214
        std::numeric_limits<Capacity>::max();
alpar@561
   215
 
alpar@385
   216
    while (is >> c) {
alpar@385
   217
      switch (c) {
alpar@385
   218
      case 'c': // comment line
alpar@385
   219
        getline(is, str);
alpar@385
   220
        break;
alpar@385
   221
      case 'n': // node definition line
alpar@387
   222
        if (desc.type==DimacsDescriptor::SP) { // shortest path problem
alpar@385
   223
          is >> i;
alpar@385
   224
          getline(is, str);
alpar@385
   225
          s = nodes[i];
alpar@385
   226
        }
alpar@387
   227
        if (desc.type==DimacsDescriptor::MAX) { // max flow problem
alpar@385
   228
          is >> i >> d;
alpar@385
   229
          getline(is, str);
alpar@385
   230
          if (d == 's') s = nodes[i];
alpar@385
   231
          if (d == 't') t = nodes[i];
alpar@385
   232
        }
alpar@385
   233
        break;
alpar@561
   234
      case 'a': // arc definition line
alpar@561
   235
        if (desc.type==DimacsDescriptor::SP) {
alpar@385
   236
          is >> i >> j >> _cap;
alpar@385
   237
          getline(is, str);
alpar@385
   238
          e = g.addArc(nodes[i], nodes[j]);
alpar@385
   239
          capacity.set(e, _cap);
alpar@561
   240
        } 
alpar@561
   241
        else if (desc.type==DimacsDescriptor::MAX) {
alpar@561
   242
          is >> i >> j >> _cap;
alpar@561
   243
          getline(is, str);
alpar@561
   244
          e = g.addArc(nodes[i], nodes[j]);
alpar@561
   245
          if (_cap >= 0)
alpar@561
   246
            capacity.set(e, _cap);
alpar@561
   247
          else
alpar@561
   248
            capacity.set(e, infty);
alpar@561
   249
        }
alpar@561
   250
        else {
alpar@385
   251
          is >> i >> j;
alpar@385
   252
          getline(is, str);
alpar@385
   253
          g.addArc(nodes[i], nodes[j]);
alpar@385
   254
        }
alpar@385
   255
        break;
alpar@385
   256
      }
alpar@385
   257
    }
alpar@385
   258
  }
alpar@385
   259
kpeter@584
   260
  /// \brief DIMACS maximum flow reader function.
alpar@387
   261
  ///
kpeter@388
   262
  /// This function reads a maximum flow instance from DIMACS format,
kpeter@388
   263
  /// i.e. from a DIMACS file having a line starting with
alpar@387
   264
  /// \code
alpar@387
   265
  ///   p max
alpar@387
   266
  /// \endcode
alpar@387
   267
  /// At the beginning, \c g is cleared by \c g.clear(). The arc
alpar@561
   268
  /// capacities are written to the \c capacity arc map and \c s and
alpar@561
   269
  /// \c t are set to the source and the target nodes.
alpar@561
   270
  ///
alpar@561
   271
  /// If the capacity of an arc is negative, it will
alpar@561
   272
  /// be set to "infinite" instead. The actual value of "infinite" is
alpar@561
   273
  /// contolled by the \c infty parameter. If it is 0 (the default value),
alpar@561
   274
  /// \c std::numeric_limits<Capacity>::infinity() will be used if available,
alpar@561
   275
  /// \c std::numeric_limits<Capacity>::max() otherwise. If \c infty is set to
alpar@561
   276
  /// a non-zero value, that value will be used as "infinite".
alpar@387
   277
  ///
alpar@387
   278
  /// If the file type was previously evaluated by dimacsType(), then
alpar@387
   279
  /// the descriptor struct should be given by the \c dest parameter.
alpar@387
   280
  template<typename Digraph, typename CapacityMap>
alpar@387
   281
  void readDimacsMax(std::istream& is,
alpar@387
   282
                     Digraph &g,
alpar@387
   283
                     CapacityMap& capacity,
alpar@387
   284
                     typename Digraph::Node &s,
alpar@387
   285
                     typename Digraph::Node &t,
alpar@561
   286
                     typename CapacityMap::Value infty = 0,
alpar@387
   287
                     DimacsDescriptor desc=DimacsDescriptor()) {
alpar@387
   288
    if(desc.type==DimacsDescriptor::NONE) desc=dimacsType(is);
alpar@387
   289
    if(desc.type!=DimacsDescriptor::MAX)
alpar@387
   290
      throw FormatError("Problem type mismatch");
alpar@561
   291
    _readDimacs(is,g,capacity,s,t,infty,desc);
alpar@387
   292
  }
alpar@387
   293
kpeter@584
   294
  /// \brief DIMACS shortest path reader function.
alpar@385
   295
  ///
alpar@385
   296
  /// This function reads a shortest path instance from DIMACS format,
kpeter@388
   297
  /// i.e. from a DIMACS file having a line starting with
alpar@385
   298
  /// \code
alpar@385
   299
  ///   p sp
alpar@385
   300
  /// \endcode
alpar@387
   301
  /// At the beginning, \c g is cleared by \c g.clear(). The arc
alpar@561
   302
  /// lengths are written to the \c length arc map and \c s is set to the
alpar@385
   303
  /// source node.
alpar@387
   304
  ///
alpar@387
   305
  /// If the file type was previously evaluated by dimacsType(), then
alpar@387
   306
  /// the descriptor struct should be given by the \c dest parameter.
alpar@387
   307
  template<typename Digraph, typename LengthMap>
alpar@387
   308
  void readDimacsSp(std::istream& is,
alpar@387
   309
                    Digraph &g,
alpar@387
   310
                    LengthMap& length,
alpar@387
   311
                    typename Digraph::Node &s,
alpar@387
   312
                    DimacsDescriptor desc=DimacsDescriptor()) {
alpar@386
   313
    typename Digraph::Node t;
alpar@387
   314
    if(desc.type==DimacsDescriptor::NONE) desc=dimacsType(is);
alpar@387
   315
    if(desc.type!=DimacsDescriptor::SP)
alpar@387
   316
      throw FormatError("Problem type mismatch");
alpar@561
   317
    _readDimacs(is, g, length, s, t, 0, desc);
alpar@385
   318
  }
alpar@385
   319
kpeter@584
   320
  /// \brief DIMACS capacitated digraph reader function.
alpar@385
   321
  ///
alpar@385
   322
  /// This function reads an arc capacitated digraph instance from
alpar@561
   323
  /// DIMACS 'max' or 'sp' format.
alpar@387
   324
  /// At the beginning, \c g is cleared by \c g.clear()
alpar@561
   325
  /// and the arc capacities/lengths are written to the \c capacity
alpar@561
   326
  /// arc map.
alpar@561
   327
  ///
alpar@561
   328
  /// In case of the 'max' format, if the capacity of an arc is negative,
alpar@561
   329
  /// it will
alpar@561
   330
  /// be set to "infinite" instead. The actual value of "infinite" is
alpar@561
   331
  /// contolled by the \c infty parameter. If it is 0 (the default value),
alpar@561
   332
  /// \c std::numeric_limits<Capacity>::infinity() will be used if available,
alpar@561
   333
  /// \c std::numeric_limits<Capacity>::max() otherwise. If \c infty is set to
alpar@561
   334
  /// a non-zero value, that value will be used as "infinite".
alpar@387
   335
  ///
alpar@387
   336
  /// If the file type was previously evaluated by dimacsType(), then
alpar@387
   337
  /// the descriptor struct should be given by the \c dest parameter.
alpar@385
   338
  template<typename Digraph, typename CapacityMap>
alpar@387
   339
  void readDimacsCap(std::istream& is,
alpar@387
   340
                     Digraph &g,
alpar@387
   341
                     CapacityMap& capacity,
alpar@561
   342
                     typename CapacityMap::Value infty = 0,
alpar@387
   343
                     DimacsDescriptor desc=DimacsDescriptor()) {
alpar@386
   344
    typename Digraph::Node u,v;
alpar@387
   345
    if(desc.type==DimacsDescriptor::NONE) desc=dimacsType(is);
alpar@387
   346
    if(desc.type!=DimacsDescriptor::MAX || desc.type!=DimacsDescriptor::SP)
alpar@387
   347
      throw FormatError("Problem type mismatch");
alpar@561
   348
    _readDimacs(is, g, capacity, u, v, infty, desc);
alpar@385
   349
  }
alpar@385
   350
alpar@525
   351
  template<typename Graph>
alpar@525
   352
  typename enable_if<lemon::UndirectedTagIndicator<Graph>,void>::type
alpar@525
   353
  _addArcEdge(Graph &g, typename Graph::Node s, typename Graph::Node t,
alpar@525
   354
              dummy<0> = 0)
alpar@525
   355
  {
alpar@525
   356
    g.addEdge(s,t);
alpar@525
   357
  }
alpar@525
   358
  template<typename Graph>
alpar@525
   359
  typename disable_if<lemon::UndirectedTagIndicator<Graph>,void>::type
alpar@525
   360
  _addArcEdge(Graph &g, typename Graph::Node s, typename Graph::Node t,
alpar@525
   361
              dummy<1> = 1)
alpar@525
   362
  {
alpar@525
   363
    g.addArc(s,t);
alpar@525
   364
  }
alpar@525
   365
  
kpeter@584
   366
  /// \brief DIMACS plain (di)graph reader function.
alpar@385
   367
  ///
kpeter@584
   368
  /// This function reads a plain (di)graph without any designated nodes
kpeter@584
   369
  /// and maps (e.g. a matching instance) from DIMACS format, i.e. from 
kpeter@584
   370
  /// DIMACS files having a line starting with
alpar@385
   371
  /// \code
alpar@385
   372
  ///   p mat
alpar@385
   373
  /// \endcode
alpar@387
   374
  /// At the beginning, \c g is cleared by \c g.clear().
alpar@387
   375
  ///
alpar@387
   376
  /// If the file type was previously evaluated by dimacsType(), then
alpar@387
   377
  /// the descriptor struct should be given by the \c dest parameter.
alpar@525
   378
  template<typename Graph>
alpar@525
   379
  void readDimacsMat(std::istream& is, Graph &g,
alpar@525
   380
                     DimacsDescriptor desc=DimacsDescriptor())
alpar@525
   381
  {
alpar@387
   382
    if(desc.type==DimacsDescriptor::NONE) desc=dimacsType(is);
alpar@387
   383
    if(desc.type!=DimacsDescriptor::MAT)
alpar@387
   384
      throw FormatError("Problem type mismatch");
alpar@525
   385
alpar@525
   386
    g.clear();
alpar@525
   387
    std::vector<typename Graph::Node> nodes;
alpar@525
   388
    char c;
alpar@525
   389
    int i, j;
alpar@525
   390
    std::string str;
alpar@525
   391
    nodes.resize(desc.nodeNum + 1);
alpar@525
   392
    for (int k = 1; k <= desc.nodeNum; ++k) {
alpar@525
   393
      nodes[k] = g.addNode();
alpar@525
   394
    }
alpar@525
   395
    
alpar@525
   396
    while (is >> c) {
alpar@525
   397
      switch (c) {
alpar@525
   398
      case 'c': // comment line
alpar@525
   399
        getline(is, str);
alpar@525
   400
        break;
alpar@525
   401
      case 'n': // node definition line
alpar@525
   402
        break;
alpar@561
   403
      case 'a': // arc definition line
alpar@525
   404
        is >> i >> j;
alpar@525
   405
        getline(is, str);
alpar@525
   406
        _addArcEdge(g,nodes[i], nodes[j]);
alpar@525
   407
        break;
alpar@525
   408
      }
alpar@525
   409
    }
alpar@385
   410
  }
alpar@385
   411
alpar@385
   412
  /// DIMACS plain digraph writer function.
alpar@385
   413
  ///
alpar@385
   414
  /// This function writes a digraph without any designated nodes and
alpar@385
   415
  /// maps into DIMACS format, i.e. into DIMACS file having a line
alpar@385
   416
  /// starting with
alpar@385
   417
  /// \code
alpar@385
   418
  ///   p mat
alpar@385
   419
  /// \endcode
alpar@387
   420
  /// If \c comment is not empty, then it will be printed in the first line
alpar@387
   421
  /// prefixed by 'c'.
alpar@385
   422
  template<typename Digraph>
alpar@387
   423
  void writeDimacsMat(std::ostream& os, const Digraph &g,
alpar@387
   424
                      std::string comment="") {
alpar@385
   425
    typedef typename Digraph::NodeIt NodeIt;
alpar@385
   426
    typedef typename Digraph::ArcIt ArcIt;
alpar@385
   427
alpar@440
   428
    if(!comment.empty())
alpar@387
   429
      os << "c " << comment << std::endl;
alpar@385
   430
    os << "p mat " << g.nodeNum() << " " << g.arcNum() << std::endl;
alpar@385
   431
alpar@385
   432
    typename Digraph::template NodeMap<int> nodes(g);
alpar@385
   433
    int i = 1;
alpar@385
   434
    for(NodeIt v(g); v != INVALID; ++v) {
alpar@385
   435
      nodes.set(v, i);
alpar@385
   436
      ++i;
alpar@385
   437
    }
alpar@385
   438
    for(ArcIt e(g); e != INVALID; ++e) {
alpar@385
   439
      os << "a " << nodes[g.source(e)] << " " << nodes[g.target(e)]
alpar@385
   440
         << std::endl;
alpar@385
   441
    }
alpar@385
   442
  }
alpar@385
   443
alpar@385
   444
  /// @}
alpar@385
   445
alpar@385
   446
} //namespace lemon
alpar@385
   447
alpar@385
   448
#endif //LEMON_DIMACS_H