COIN-OR::LEMON - Graph Library

source: lemon/lemon/smart_graph.h @ 157:2ccc1afc2c52

Last change on this file since 157:2ccc1afc2c52 was 157:2ccc1afc2c52, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Using \tparam commands + removing \author commands (ticket #29, #39)

File size: 21.7 KB
Line 
1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_SMART_GRAPH_H
20#define LEMON_SMART_GRAPH_H
21
22///\ingroup graphs
23///\file
24///\brief SmartDigraph and SmartGraph classes.
25
26#include <vector>
27
28#include <lemon/bits/invalid.h>
29
30#include <lemon/bits/base_extender.h>
31#include <lemon/bits/graph_extender.h>
32
33#include <lemon/bits/utility.h>
34#include <lemon/error.h>
35
36#include <lemon/bits/graph_extender.h>
37
38namespace lemon {
39
40  class SmartDigraph;
41  ///Base of SmartDigraph
42
43  ///Base of SmartDigraph
44  ///
45  class SmartDigraphBase {
46  protected:
47
48    struct NodeT
49    {
50      int first_in, first_out;     
51      NodeT() {}
52    };
53    struct ArcT
54    {
55      int target, source, next_in, next_out;     
56      ArcT() {} 
57    };
58
59    std::vector<NodeT> nodes;
60    std::vector<ArcT> arcs;
61       
62  public:
63
64    typedef SmartDigraphBase Graph;
65
66    class Node;
67    class Arc;
68
69  public:
70
71    SmartDigraphBase() : nodes(), arcs() { }
72    SmartDigraphBase(const SmartDigraphBase &_g)
73      : nodes(_g.nodes), arcs(_g.arcs) { }
74   
75    typedef True NodeNumTag;
76    typedef True EdgeNumTag;
77
78    int nodeNum() const { return nodes.size(); }
79    int arcNum() const { return arcs.size(); }
80
81    int maxNodeId() const { return nodes.size()-1; }
82    int maxArcId() const { return arcs.size()-1; }
83
84    Node addNode() {
85      int n = nodes.size();     
86      nodes.push_back(NodeT());
87      nodes[n].first_in = -1;
88      nodes[n].first_out = -1;
89      return Node(n);
90    }
91   
92    Arc addArc(Node u, Node v) {
93      int n = arcs.size();
94      arcs.push_back(ArcT());
95      arcs[n].source = u._id;
96      arcs[n].target = v._id;
97      arcs[n].next_out = nodes[u._id].first_out;
98      arcs[n].next_in = nodes[v._id].first_in;
99      nodes[u._id].first_out = nodes[v._id].first_in = n;
100
101      return Arc(n);
102    }
103
104    void clear() {
105      arcs.clear();
106      nodes.clear();
107    }
108
109    Node source(Arc a) const { return Node(arcs[a._id].source); }
110    Node target(Arc a) const { return Node(arcs[a._id].target); }
111
112    static int id(Node v) { return v._id; }
113    static int id(Arc a) { return a._id; }
114
115    static Node nodeFromId(int id) { return Node(id);}
116    static Arc arcFromId(int id) { return Arc(id);}
117
118    bool valid(Node n) const {
119      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
120    }
121    bool valid(Arc a) const {
122      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
123    }
124
125    class Node {
126      friend class SmartDigraphBase;
127      friend class SmartDigraph;
128
129    protected:
130      int _id;
131      explicit Node(int id) : _id(id) {}
132    public:
133      Node() {}
134      Node (Invalid) : _id(-1) {}
135      bool operator==(const Node i) const {return _id == i._id;}
136      bool operator!=(const Node i) const {return _id != i._id;}
137      bool operator<(const Node i) const {return _id < i._id;}
138    };
139   
140
141    class Arc {
142      friend class SmartDigraphBase;
143      friend class SmartDigraph;
144
145    protected:
146      int _id;
147      explicit Arc(int id) : _id(id) {}
148    public:
149      Arc() { }
150      Arc (Invalid) : _id(-1) {}
151      bool operator==(const Arc i) const {return _id == i._id;}
152      bool operator!=(const Arc i) const {return _id != i._id;}
153      bool operator<(const Arc i) const {return _id < i._id;}
154    };
155
156    void first(Node& node) const {
157      node._id = nodes.size() - 1;
158    }
159
160    static void next(Node& node) {
161      --node._id;
162    }
163
164    void first(Arc& arc) const {
165      arc._id = arcs.size() - 1;
166    }
167
168    static void next(Arc& arc) {
169      --arc._id;
170    }
171
172    void firstOut(Arc& arc, const Node& node) const {
173      arc._id = nodes[node._id].first_out;
174    }
175
176    void nextOut(Arc& arc) const {
177      arc._id = arcs[arc._id].next_out;
178    }
179
180    void firstIn(Arc& arc, const Node& node) const {
181      arc._id = nodes[node._id].first_in;
182    }
183   
184    void nextIn(Arc& arc) const {
185      arc._id = arcs[arc._id].next_in;
186    }
187
188  };
189
190  typedef DigraphExtender<SmartDigraphBase> ExtendedSmartDigraphBase;
191
192  ///\ingroup graphs
193  ///
194  ///\brief A smart directed graph class.
195  ///
196  ///This is a simple and fast digraph implementation.
197  ///It is also quite memory efficient, but at the price
198  ///that <b> it does support only limited (only stack-like)
199  ///node and arc deletions</b>.
200  ///It conforms to the \ref concepts::Digraph "Digraph concept" with
201  ///an important extra feature that its maps are real \ref
202  ///concepts::ReferenceMap "reference map"s.
203  ///
204  ///\sa concepts::Digraph.
205  class SmartDigraph : public ExtendedSmartDigraphBase {
206  public:
207
208    typedef ExtendedSmartDigraphBase Parent;
209
210  private:
211
212    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
213
214    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
215    ///
216    SmartDigraph(const SmartDigraph &) : ExtendedSmartDigraphBase() {};
217    ///\brief Assignment of SmartDigraph to another one is \e not allowed.
218    ///Use DigraphCopy() instead.
219
220    ///Assignment of SmartDigraph to another one is \e not allowed.
221    ///Use DigraphCopy() instead.
222    void operator=(const SmartDigraph &) {}
223
224  public:
225   
226    /// Constructor
227   
228    /// Constructor.
229    ///
230    SmartDigraph() {};
231   
232    ///Add a new node to the digraph.
233   
234    /// \return the new node.
235    ///
236    Node addNode() { return Parent::addNode(); }
237   
238    ///Add a new arc to the digraph.
239   
240    ///Add a new arc to the digraph with source node \c s
241    ///and target node \c t.
242    ///\return the new arc.
243    Arc addArc(const Node& s, const Node& t) {
244      return Parent::addArc(s, t);
245    }
246
247    /// \brief Using this it is possible to avoid the superfluous memory
248    /// allocation.
249
250    /// Using this it is possible to avoid the superfluous memory
251    /// allocation: if you know that the digraph you want to build will
252    /// be very large (e.g. it will contain millions of nodes and/or arcs)
253    /// then it is worth reserving space for this amount before starting
254    /// to build the digraph.
255    /// \sa reserveArc
256    void reserveNode(int n) { nodes.reserve(n); };
257
258    /// \brief Using this it is possible to avoid the superfluous memory
259    /// allocation.
260
261    /// Using this it is possible to avoid the superfluous memory
262    /// allocation: if you know that the digraph you want to build will
263    /// be very large (e.g. it will contain millions of nodes and/or arcs)
264    /// then it is worth reserving space for this amount before starting
265    /// to build the digraph.
266    /// \sa reserveNode
267    void reserveArc(int m) { arcs.reserve(m); };
268
269    /// \brief Node validity check
270    ///
271    /// This function gives back true if the given node is valid,
272    /// ie. it is a real node of the graph. 
273    ///
274    /// \warning A removed node (using Snapshot) could become valid again
275    /// when new nodes are added to the graph.
276    bool valid(Node n) const { return Parent::valid(n); }
277
278    /// \brief Arc validity check
279    ///
280    /// This function gives back true if the given arc is valid,
281    /// ie. it is a real arc of the graph. 
282    ///
283    /// \warning A removed arc (using Snapshot) could become valid again
284    /// when new arcs are added to the graph.
285    bool valid(Arc a) const { return Parent::valid(a); }
286
287    ///Clear the digraph.
288   
289    ///Erase all the nodes and arcs from the digraph.
290    ///
291    void clear() {
292      Parent::clear();
293    }
294
295    ///Split a node.
296   
297    ///This function splits a node. First a new node is added to the digraph,
298    ///then the source of each outgoing arc of \c n is moved to this new node.
299    ///If \c connect is \c true (this is the default value), then a new arc
300    ///from \c n to the newly created node is also added.
301    ///\return The newly created node.
302    ///
303    ///\note The <tt>Arc</tt>s
304    ///referencing a moved arc remain
305    ///valid. However <tt>InArc</tt>'s and <tt>OutArc</tt>'s
306    ///may be invalidated.
307    ///\warning This functionality cannot be used together with the Snapshot
308    ///feature.
309    ///\todo It could be implemented in a bit faster way.
310    Node split(Node n, bool connect = true)
311    {
312      Node b = addNode();
313      nodes[b._id].first_out=nodes[n._id].first_out;
314      nodes[n._id].first_out=-1;
315      for(int i=nodes[b._id].first_out;i!=-1;i++) arcs[i].source=b._id;
316      if(connect) addArc(n,b);
317      return b;
318    }
319
320  public:
321   
322    class Snapshot;
323
324  protected:
325
326    void restoreSnapshot(const Snapshot &s)
327    {
328      while(s.arc_num<arcs.size()) {
329        Arc arc = arcFromId(arcs.size()-1);
330        Parent::notifier(Arc()).erase(arc);
331        nodes[arcs.back().source].first_out=arcs.back().next_out;
332        nodes[arcs.back().target].first_in=arcs.back().next_in;
333        arcs.pop_back();
334      }
335      while(s.node_num<nodes.size()) {
336        Node node = nodeFromId(nodes.size()-1);
337        Parent::notifier(Node()).erase(node);
338        nodes.pop_back();
339      }
340    }   
341
342  public:
343
344    ///Class to make a snapshot of the digraph and to restrore to it later.
345
346    ///Class to make a snapshot of the digraph and to restrore to it later.
347    ///
348    ///The newly added nodes and arcs can be removed using the
349    ///restore() function.
350    ///\note After you restore a state, you cannot restore
351    ///a later state, in other word you cannot add again the arcs deleted
352    ///by restore() using another one Snapshot instance.
353    ///
354    ///\warning If you do not use correctly the snapshot that can cause
355    ///either broken program, invalid state of the digraph, valid but
356    ///not the restored digraph or no change. Because the runtime performance
357    ///the validity of the snapshot is not stored.
358    class Snapshot
359    {
360      SmartDigraph *_graph;
361    protected:
362      friend class SmartDigraph;
363      unsigned int node_num;
364      unsigned int arc_num;
365    public:
366      ///Default constructor.
367     
368      ///Default constructor.
369      ///To actually make a snapshot you must call save().
370      ///
371      Snapshot() : _graph(0) {}
372      ///Constructor that immediately makes a snapshot
373     
374      ///This constructor immediately makes a snapshot of the digraph.
375      ///\param _g The digraph we make a snapshot of.
376      Snapshot(SmartDigraph &graph) : _graph(&graph) {
377        node_num=_graph->nodes.size();
378        arc_num=_graph->arcs.size();
379      }
380
381      ///Make a snapshot.
382
383      ///Make a snapshot of the digraph.
384      ///
385      ///This function can be called more than once. In case of a repeated
386      ///call, the previous snapshot gets lost.
387      ///\param _g The digraph we make the snapshot of.
388      void save(SmartDigraph &graph)
389      {
390        _graph=&graph;
391        node_num=_graph->nodes.size();
392        arc_num=_graph->arcs.size();
393      }
394
395      ///Undo the changes until a snapshot.
396     
397      ///Undo the changes until a snapshot created by save().
398      ///
399      ///\note After you restored a state, you cannot restore
400      ///a later state, in other word you cannot add again the arcs deleted
401      ///by restore().
402      void restore()
403      {
404        _graph->restoreSnapshot(*this);
405      }
406    };
407  };
408
409
410  class SmartGraphBase {
411
412  protected:
413
414    struct NodeT {
415      int first_out;
416    };
417 
418    struct ArcT {
419      int target;
420      int next_out;
421    };
422
423    std::vector<NodeT> nodes;
424    std::vector<ArcT> arcs;
425
426    int first_free_arc;
427   
428  public:
429   
430    typedef SmartGraphBase Digraph;
431
432    class Node;
433    class Arc;
434    class Edge;
435   
436    class Node {
437      friend class SmartGraphBase;
438    protected:
439
440      int _id;
441      explicit Node(int id) { _id = id;}
442
443    public:
444      Node() {}
445      Node (Invalid) { _id = -1; }
446      bool operator==(const Node& node) const {return _id == node._id;}
447      bool operator!=(const Node& node) const {return _id != node._id;}
448      bool operator<(const Node& node) const {return _id < node._id;}
449    };
450
451    class Edge {
452      friend class SmartGraphBase;
453    protected:
454
455      int _id;
456      explicit Edge(int id) { _id = id;}
457
458    public:
459      Edge() {}
460      Edge (Invalid) { _id = -1; }
461      bool operator==(const Edge& arc) const {return _id == arc._id;}
462      bool operator!=(const Edge& arc) const {return _id != arc._id;}
463      bool operator<(const Edge& arc) const {return _id < arc._id;}
464    };
465
466    class Arc {
467      friend class SmartGraphBase;
468    protected:
469
470      int _id;
471      explicit Arc(int id) { _id = id;}
472
473    public:
474      operator Edge() const { return edgeFromId(_id / 2); }
475
476      Arc() {}
477      Arc (Invalid) { _id = -1; }
478      bool operator==(const Arc& arc) const {return _id == arc._id;}
479      bool operator!=(const Arc& arc) const {return _id != arc._id;}
480      bool operator<(const Arc& arc) const {return _id < arc._id;}
481    };
482
483
484
485    SmartGraphBase()
486      : nodes(), arcs() {}
487
488   
489    int maxNodeId() const { return nodes.size()-1; }
490    int maxEdgeId() const { return arcs.size() / 2 - 1; }
491    int maxArcId() const { return arcs.size()-1; }
492
493    Node source(Arc e) const { return Node(arcs[e._id ^ 1].target); }
494    Node target(Arc e) const { return Node(arcs[e._id].target); }
495
496    Node u(Edge e) const { return Node(arcs[2 * e._id].target); }
497    Node v(Edge e) const { return Node(arcs[2 * e._id + 1].target); }
498
499    static bool direction(Arc e) {
500      return (e._id & 1) == 1;
501    }
502
503    static Arc direct(Edge e, bool d) {
504      return Arc(e._id * 2 + (d ? 1 : 0));
505    }
506
507    void first(Node& node) const {
508      node._id = nodes.size() - 1;
509    }
510
511    void next(Node& node) const {
512      --node._id;
513    }
514
515    void first(Arc& arc) const {
516      arc._id = arcs.size() - 1;
517    }
518
519    void next(Arc& arc) const {
520      --arc._id;
521    }
522
523    void first(Edge& arc) const {
524      arc._id = arcs.size() / 2 - 1;
525    }
526
527    void next(Edge& arc) const {
528      --arc._id;
529    }
530
531    void firstOut(Arc &arc, const Node& v) const {
532      arc._id = nodes[v._id].first_out;
533    }
534    void nextOut(Arc &arc) const {
535      arc._id = arcs[arc._id].next_out;
536    }
537
538    void firstIn(Arc &arc, const Node& v) const {
539      arc._id = ((nodes[v._id].first_out) ^ 1);
540      if (arc._id == -2) arc._id = -1;
541    }
542    void nextIn(Arc &arc) const {
543      arc._id = ((arcs[arc._id ^ 1].next_out) ^ 1);
544      if (arc._id == -2) arc._id = -1;
545    }
546
547    void firstInc(Edge &arc, bool& d, const Node& v) const {
548      int de = nodes[v._id].first_out;
549      if (de != -1) {
550        arc._id = de / 2;
551        d = ((de & 1) == 1);
552      } else {
553        arc._id = -1;
554        d = true;
555      }
556    }
557    void nextInc(Edge &arc, bool& d) const {
558      int de = (arcs[(arc._id * 2) | (d ? 1 : 0)].next_out);
559      if (de != -1) {
560        arc._id = de / 2;
561        d = ((de & 1) == 1);
562      } else {
563        arc._id = -1;
564        d = true;     
565      }
566    }
567   
568    static int id(Node v) { return v._id; }
569    static int id(Arc e) { return e._id; }
570    static int id(Edge e) { return e._id; }
571
572    static Node nodeFromId(int id) { return Node(id);}
573    static Arc arcFromId(int id) { return Arc(id);}
574    static Edge edgeFromId(int id) { return Edge(id);}
575
576    bool valid(Node n) const {
577      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
578    }
579    bool valid(Arc a) const {
580      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
581    }
582    bool valid(Edge e) const {
583      return e._id >= 0 && 2 * e._id < static_cast<int>(arcs.size());
584    }
585
586    Node addNode() {     
587      int n = nodes.size();
588      nodes.push_back(NodeT());
589      nodes[n].first_out = -1;
590     
591      return Node(n);
592    }
593   
594    Edge addEdge(Node u, Node v) {
595      int n = arcs.size();
596      arcs.push_back(ArcT());
597      arcs.push_back(ArcT());
598     
599      arcs[n].target = u._id;
600      arcs[n | 1].target = v._id;
601
602      arcs[n].next_out = nodes[v._id].first_out;
603      nodes[v._id].first_out = n;
604
605      arcs[n | 1].next_out = nodes[u._id].first_out;   
606      nodes[u._id].first_out = (n | 1);
607
608      return Edge(n / 2);
609    }
610   
611    void clear() {
612      arcs.clear();
613      nodes.clear();
614    }
615
616  };
617
618  typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;
619
620  /// \ingroup graphs
621  ///
622  /// \brief A smart undirected graph class.
623  ///
624  /// This is a simple and fast graph implementation.
625  /// It is also quite memory efficient, but at the price
626  /// that <b> it does support only limited (only stack-like)
627  /// node and arc deletions</b>.
628  /// Except from this it conforms to
629  /// the \ref concepts::Graph "Graph concept".
630  ///
631  /// It also has an
632  /// important extra feature that
633  /// its maps are real \ref concepts::ReferenceMap "reference map"s.
634  ///
635  /// \sa concepts::Graph.
636  ///
637  class SmartGraph : public ExtendedSmartGraphBase {
638  private:
639
640    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
641
642    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
643    ///
644    SmartGraph(const SmartGraph &) : ExtendedSmartGraphBase() {};
645
646    ///\brief Assignment of SmartGraph to another one is \e not allowed.
647    ///Use GraphCopy() instead.
648
649    ///Assignment of SmartGraph to another one is \e not allowed.
650    ///Use GraphCopy() instead.
651    void operator=(const SmartGraph &) {}
652
653  public:
654
655    typedef ExtendedSmartGraphBase Parent;
656
657    /// Constructor
658   
659    /// Constructor.
660    ///
661    SmartGraph() {}
662
663    ///Add a new node to the graph.
664   
665    /// \return the new node.
666    ///
667    Node addNode() { return Parent::addNode(); }
668   
669    ///Add a new edge to the graph.
670   
671    ///Add a new edge to the graph with node \c s
672    ///and \c t.
673    ///\return the new edge.
674    Edge addEdge(const Node& s, const Node& t) {
675      return Parent::addEdge(s, t);
676    }
677
678    /// \brief Node validity check
679    ///
680    /// This function gives back true if the given node is valid,
681    /// ie. it is a real node of the graph. 
682    ///
683    /// \warning A removed node (using Snapshot) could become valid again
684    /// when new nodes are added to the graph.
685    bool valid(Node n) const { return Parent::valid(n); }
686
687    /// \brief Arc validity check
688    ///
689    /// This function gives back true if the given arc is valid,
690    /// ie. it is a real arc of the graph. 
691    ///
692    /// \warning A removed arc (using Snapshot) could become valid again
693    /// when new edges are added to the graph.
694    bool valid(Arc a) const { return Parent::valid(a); }
695
696    /// \brief Edge validity check
697    ///
698    /// This function gives back true if the given edge is valid,
699    /// ie. it is a real edge of the graph. 
700    ///
701    /// \warning A removed edge (using Snapshot) could become valid again
702    /// when new edges are added to the graph.
703    bool valid(Edge e) const { return Parent::valid(e); }
704
705    ///Clear the graph.
706   
707    ///Erase all the nodes and edges from the graph.
708    ///
709    void clear() {
710      Parent::clear();
711    }
712
713  public:
714   
715    class Snapshot;
716
717  protected:
718
719    void saveSnapshot(Snapshot &s)
720    {
721      s._graph = this;
722      s.node_num = nodes.size();
723      s.arc_num = arcs.size();
724    }
725
726    void restoreSnapshot(const Snapshot &s)
727    {
728      while(s.arc_num<arcs.size()) {
729        int n=arcs.size()-1;
730        Edge arc=edgeFromId(n/2);
731        Parent::notifier(Edge()).erase(arc);
732        std::vector<Arc> dir;
733        dir.push_back(arcFromId(n));
734        dir.push_back(arcFromId(n-1));
735        Parent::notifier(Arc()).erase(dir);
736        nodes[arcs[n].target].first_out=arcs[n].next_out;
737        nodes[arcs[n-1].target].first_out=arcs[n-1].next_out;
738        arcs.pop_back();
739        arcs.pop_back();
740      }
741      while(s.node_num<nodes.size()) {
742        int n=nodes.size()-1;
743        Node node = nodeFromId(n);
744        Parent::notifier(Node()).erase(node);
745        nodes.pop_back();
746      }
747    }   
748
749  public:
750
751    ///Class to make a snapshot of the digraph and to restrore to it later.
752
753    ///Class to make a snapshot of the digraph and to restrore to it later.
754    ///
755    ///The newly added nodes and arcs can be removed using the
756    ///restore() function.
757    ///
758    ///\note After you restore a state, you cannot restore
759    ///a later state, in other word you cannot add again the arcs deleted
760    ///by restore() using another one Snapshot instance.
761    ///
762    ///\warning If you do not use correctly the snapshot that can cause
763    ///either broken program, invalid state of the digraph, valid but
764    ///not the restored digraph or no change. Because the runtime performance
765    ///the validity of the snapshot is not stored.
766    class Snapshot
767    {
768      SmartGraph *_graph;
769    protected:
770      friend class SmartGraph;
771      unsigned int node_num;
772      unsigned int arc_num;
773    public:
774      ///Default constructor.
775     
776      ///Default constructor.
777      ///To actually make a snapshot you must call save().
778      ///
779      Snapshot() : _graph(0) {}
780      ///Constructor that immediately makes a snapshot
781     
782      ///This constructor immediately makes a snapshot of the digraph.
783      ///\param g The digraph we make a snapshot of.
784      Snapshot(SmartGraph &graph) {
785        graph.saveSnapshot(*this);
786      }
787
788      ///Make a snapshot.
789
790      ///Make a snapshot of the graph.
791      ///
792      ///This function can be called more than once. In case of a repeated
793      ///call, the previous snapshot gets lost.
794      ///\param g The digraph we make the snapshot of.
795      void save(SmartGraph &graph)
796      {
797        graph.saveSnapshot(*this);
798      }
799
800      ///Undo the changes until a snapshot.
801     
802      ///Undo the changes until a snapshot created by save().
803      ///
804      ///\note After you restored a state, you cannot restore
805      ///a later state, in other word you cannot add again the arcs deleted
806      ///by restore().
807      void restore()
808      {
809        _graph->restoreSnapshot(*this);
810      }
811    };
812  };
813 
814} //namespace lemon
815
816
817#endif //LEMON_SMART_GRAPH_H
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