COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/smart_graph.h @ 705:39a5b48bcace

Last change on this file since 705:39a5b48bcace was 617:4137ef9aacc6, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Fix and uniform the usage of Graph and Parent typedefs (#268)

  • Rename Graph typedefs to GraphType? in the implementation of graph maps and MapExtender? to prevent conflicts (especially using VS). They are not public.
  • Make Parent typedefs private in all classes.
  • Replace Digraph with Graph in some places (fix faulty renamings of the script).
  • Use Graph and Digraph typedefs (more) consequently.
File size: 21.5 KB
Line 
1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2009
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/core.h>
29#include <lemon/error.h>
30#include <lemon/bits/graph_extender.h>
31
32namespace lemon {
33
34  class SmartDigraph;
35  ///Base of SmartDigraph
36
37  ///Base of SmartDigraph
38  ///
39  class SmartDigraphBase {
40  protected:
41
42    struct NodeT
43    {
44      int first_in, first_out;
45      NodeT() {}
46    };
47    struct ArcT
48    {
49      int target, source, next_in, next_out;
50      ArcT() {}
51    };
52
53    std::vector<NodeT> nodes;
54    std::vector<ArcT> arcs;
55
56  public:
57
58    typedef SmartDigraphBase Digraph;
59
60    class Node;
61    class Arc;
62
63  public:
64
65    SmartDigraphBase() : nodes(), arcs() { }
66    SmartDigraphBase(const SmartDigraphBase &_g)
67      : nodes(_g.nodes), arcs(_g.arcs) { }
68
69    typedef True NodeNumTag;
70    typedef True ArcNumTag;
71
72    int nodeNum() const { return nodes.size(); }
73    int arcNum() const { return arcs.size(); }
74
75    int maxNodeId() const { return nodes.size()-1; }
76    int maxArcId() const { return arcs.size()-1; }
77
78    Node addNode() {
79      int n = nodes.size();
80      nodes.push_back(NodeT());
81      nodes[n].first_in = -1;
82      nodes[n].first_out = -1;
83      return Node(n);
84    }
85
86    Arc addArc(Node u, Node v) {
87      int n = arcs.size();
88      arcs.push_back(ArcT());
89      arcs[n].source = u._id;
90      arcs[n].target = v._id;
91      arcs[n].next_out = nodes[u._id].first_out;
92      arcs[n].next_in = nodes[v._id].first_in;
93      nodes[u._id].first_out = nodes[v._id].first_in = n;
94
95      return Arc(n);
96    }
97
98    void clear() {
99      arcs.clear();
100      nodes.clear();
101    }
102
103    Node source(Arc a) const { return Node(arcs[a._id].source); }
104    Node target(Arc a) const { return Node(arcs[a._id].target); }
105
106    static int id(Node v) { return v._id; }
107    static int id(Arc a) { return a._id; }
108
109    static Node nodeFromId(int id) { return Node(id);}
110    static Arc arcFromId(int id) { return Arc(id);}
111
112    bool valid(Node n) const {
113      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
114    }
115    bool valid(Arc a) const {
116      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
117    }
118
119    class Node {
120      friend class SmartDigraphBase;
121      friend class SmartDigraph;
122
123    protected:
124      int _id;
125      explicit Node(int id) : _id(id) {}
126    public:
127      Node() {}
128      Node (Invalid) : _id(-1) {}
129      bool operator==(const Node i) const {return _id == i._id;}
130      bool operator!=(const Node i) const {return _id != i._id;}
131      bool operator<(const Node i) const {return _id < i._id;}
132    };
133
134
135    class Arc {
136      friend class SmartDigraphBase;
137      friend class SmartDigraph;
138
139    protected:
140      int _id;
141      explicit Arc(int id) : _id(id) {}
142    public:
143      Arc() { }
144      Arc (Invalid) : _id(-1) {}
145      bool operator==(const Arc i) const {return _id == i._id;}
146      bool operator!=(const Arc i) const {return _id != i._id;}
147      bool operator<(const Arc i) const {return _id < i._id;}
148    };
149
150    void first(Node& node) const {
151      node._id = nodes.size() - 1;
152    }
153
154    static void next(Node& node) {
155      --node._id;
156    }
157
158    void first(Arc& arc) const {
159      arc._id = arcs.size() - 1;
160    }
161
162    static void next(Arc& arc) {
163      --arc._id;
164    }
165
166    void firstOut(Arc& arc, const Node& node) const {
167      arc._id = nodes[node._id].first_out;
168    }
169
170    void nextOut(Arc& arc) const {
171      arc._id = arcs[arc._id].next_out;
172    }
173
174    void firstIn(Arc& arc, const Node& node) const {
175      arc._id = nodes[node._id].first_in;
176    }
177
178    void nextIn(Arc& arc) const {
179      arc._id = arcs[arc._id].next_in;
180    }
181
182  };
183
184  typedef DigraphExtender<SmartDigraphBase> ExtendedSmartDigraphBase;
185
186  ///\ingroup graphs
187  ///
188  ///\brief A smart directed graph class.
189  ///
190  ///This is a simple and fast digraph implementation.
191  ///It is also quite memory efficient, but at the price
192  ///that <b> it does support only limited (only stack-like)
193  ///node and arc deletions</b>.
194  ///It fully conforms to the \ref concepts::Digraph "Digraph concept".
195  ///
196  ///\sa concepts::Digraph.
197  class SmartDigraph : public ExtendedSmartDigraphBase {
198    typedef ExtendedSmartDigraphBase Parent;
199
200  private:
201
202    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
203
204    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
205    ///
206    SmartDigraph(const SmartDigraph &) : ExtendedSmartDigraphBase() {};
207    ///\brief Assignment of SmartDigraph to another one is \e not allowed.
208    ///Use DigraphCopy() instead.
209
210    ///Assignment of SmartDigraph to another one is \e not allowed.
211    ///Use DigraphCopy() instead.
212    void operator=(const SmartDigraph &) {}
213
214  public:
215
216    /// Constructor
217
218    /// Constructor.
219    ///
220    SmartDigraph() {};
221
222    ///Add a new node to the digraph.
223
224    /// Add a new node to the digraph.
225    /// \return The new node.
226    Node addNode() { return Parent::addNode(); }
227
228    ///Add a new arc to the digraph.
229
230    ///Add a new arc to the digraph with source node \c s
231    ///and target node \c t.
232    ///\return The new arc.
233    Arc addArc(const Node& s, const Node& t) {
234      return Parent::addArc(s, t);
235    }
236
237    /// \brief Using this it is possible to avoid the superfluous memory
238    /// allocation.
239
240    /// Using this it is possible to avoid the superfluous memory
241    /// allocation: if you know that the digraph you want to build will
242    /// be very large (e.g. it will contain millions of nodes and/or arcs)
243    /// then it is worth reserving space for this amount before starting
244    /// to build the digraph.
245    /// \sa reserveArc
246    void reserveNode(int n) { nodes.reserve(n); };
247
248    /// \brief Using this it is possible to avoid the superfluous memory
249    /// allocation.
250
251    /// Using this it is possible to avoid the superfluous memory
252    /// allocation: if you know that the digraph you want to build will
253    /// be very large (e.g. it will contain millions of nodes and/or arcs)
254    /// then it is worth reserving space for this amount before starting
255    /// to build the digraph.
256    /// \sa reserveNode
257    void reserveArc(int m) { arcs.reserve(m); };
258
259    /// \brief Node validity check
260    ///
261    /// This function gives back true if the given node is valid,
262    /// ie. it is a real node of the graph.
263    ///
264    /// \warning A removed node (using Snapshot) could become valid again
265    /// when new nodes are added to the graph.
266    bool valid(Node n) const { return Parent::valid(n); }
267
268    /// \brief Arc validity check
269    ///
270    /// This function gives back true if the given arc is valid,
271    /// ie. it is a real arc of the graph.
272    ///
273    /// \warning A removed arc (using Snapshot) could become valid again
274    /// when new arcs are added to the graph.
275    bool valid(Arc a) const { return Parent::valid(a); }
276
277    ///Clear the digraph.
278
279    ///Erase all the nodes and arcs from the digraph.
280    ///
281    void clear() {
282      Parent::clear();
283    }
284
285    ///Split a node.
286
287    ///This function splits a node. First a new node is added to the digraph,
288    ///then the source of each outgoing arc of \c n is moved to this new node.
289    ///If \c connect is \c true (this is the default value), then a new arc
290    ///from \c n to the newly created node is also added.
291    ///\return The newly created node.
292    ///
293    ///\note The <tt>Arc</tt>s
294    ///referencing a moved arc remain
295    ///valid. However <tt>InArc</tt>'s and <tt>OutArc</tt>'s
296    ///may be invalidated.
297    ///\warning This functionality cannot be used together with the Snapshot
298    ///feature.
299    Node split(Node n, bool connect = true)
300    {
301      Node b = addNode();
302      nodes[b._id].first_out=nodes[n._id].first_out;
303      nodes[n._id].first_out=-1;
304      for(int i=nodes[b._id].first_out; i!=-1; i=arcs[i].next_out) {
305        arcs[i].source=b._id;
306      }
307      if(connect) addArc(n,b);
308      return b;
309    }
310
311  public:
312
313    class Snapshot;
314
315  protected:
316
317    void restoreSnapshot(const Snapshot &s)
318    {
319      while(s.arc_num<arcs.size()) {
320        Arc arc = arcFromId(arcs.size()-1);
321        Parent::notifier(Arc()).erase(arc);
322        nodes[arcs.back().source].first_out=arcs.back().next_out;
323        nodes[arcs.back().target].first_in=arcs.back().next_in;
324        arcs.pop_back();
325      }
326      while(s.node_num<nodes.size()) {
327        Node node = nodeFromId(nodes.size()-1);
328        Parent::notifier(Node()).erase(node);
329        nodes.pop_back();
330      }
331    }
332
333  public:
334
335    ///Class to make a snapshot of the digraph and to restrore to it later.
336
337    ///Class to make a snapshot of the digraph and to restrore to it later.
338    ///
339    ///The newly added nodes and arcs can be removed using the
340    ///restore() function.
341    ///\note After you restore a state, you cannot restore
342    ///a later state, in other word you cannot add again the arcs deleted
343    ///by restore() using another one Snapshot instance.
344    ///
345    ///\warning If you do not use correctly the snapshot that can cause
346    ///either broken program, invalid state of the digraph, valid but
347    ///not the restored digraph or no change. Because the runtime performance
348    ///the validity of the snapshot is not stored.
349    class Snapshot
350    {
351      SmartDigraph *_graph;
352    protected:
353      friend class SmartDigraph;
354      unsigned int node_num;
355      unsigned int arc_num;
356    public:
357      ///Default constructor.
358
359      ///Default constructor.
360      ///To actually make a snapshot you must call save().
361      ///
362      Snapshot() : _graph(0) {}
363      ///Constructor that immediately makes a snapshot
364
365      ///This constructor immediately makes a snapshot of the digraph.
366      ///\param graph The digraph we make a snapshot of.
367      Snapshot(SmartDigraph &graph) : _graph(&graph) {
368        node_num=_graph->nodes.size();
369        arc_num=_graph->arcs.size();
370      }
371
372      ///Make a snapshot.
373
374      ///Make a snapshot of the digraph.
375      ///
376      ///This function can be called more than once. In case of a repeated
377      ///call, the previous snapshot gets lost.
378      ///\param graph The digraph we make the snapshot of.
379      void save(SmartDigraph &graph)
380      {
381        _graph=&graph;
382        node_num=_graph->nodes.size();
383        arc_num=_graph->arcs.size();
384      }
385
386      ///Undo the changes until a snapshot.
387
388      ///Undo the changes until a snapshot created by save().
389      ///
390      ///\note After you restored a state, you cannot restore
391      ///a later state, in other word you cannot add again the arcs deleted
392      ///by restore().
393      void restore()
394      {
395        _graph->restoreSnapshot(*this);
396      }
397    };
398  };
399
400
401  class SmartGraphBase {
402
403  protected:
404
405    struct NodeT {
406      int first_out;
407    };
408
409    struct ArcT {
410      int target;
411      int next_out;
412    };
413
414    std::vector<NodeT> nodes;
415    std::vector<ArcT> arcs;
416
417    int first_free_arc;
418
419  public:
420
421    typedef SmartGraphBase Graph;
422
423    class Node;
424    class Arc;
425    class Edge;
426
427    class Node {
428      friend class SmartGraphBase;
429    protected:
430
431      int _id;
432      explicit Node(int id) { _id = id;}
433
434    public:
435      Node() {}
436      Node (Invalid) { _id = -1; }
437      bool operator==(const Node& node) const {return _id == node._id;}
438      bool operator!=(const Node& node) const {return _id != node._id;}
439      bool operator<(const Node& node) const {return _id < node._id;}
440    };
441
442    class Edge {
443      friend class SmartGraphBase;
444    protected:
445
446      int _id;
447      explicit Edge(int id) { _id = id;}
448
449    public:
450      Edge() {}
451      Edge (Invalid) { _id = -1; }
452      bool operator==(const Edge& arc) const {return _id == arc._id;}
453      bool operator!=(const Edge& arc) const {return _id != arc._id;}
454      bool operator<(const Edge& arc) const {return _id < arc._id;}
455    };
456
457    class Arc {
458      friend class SmartGraphBase;
459    protected:
460
461      int _id;
462      explicit Arc(int id) { _id = id;}
463
464    public:
465      operator Edge() const {
466        return _id != -1 ? edgeFromId(_id / 2) : INVALID;
467      }
468
469      Arc() {}
470      Arc (Invalid) { _id = -1; }
471      bool operator==(const Arc& arc) const {return _id == arc._id;}
472      bool operator!=(const Arc& arc) const {return _id != arc._id;}
473      bool operator<(const Arc& arc) const {return _id < arc._id;}
474    };
475
476
477
478    SmartGraphBase()
479      : nodes(), arcs() {}
480
481    typedef True NodeNumTag;
482    typedef True EdgeNumTag;
483    typedef True ArcNumTag;
484
485    int nodeNum() const { return nodes.size(); }
486    int edgeNum() const { return arcs.size() / 2; }
487    int arcNum() const { return arcs.size(); }
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  /// It fully conforms to the \ref concepts::Graph "Graph concept".
629  ///
630  /// \sa concepts::Graph.
631  class SmartGraph : public ExtendedSmartGraphBase {
632    typedef ExtendedSmartGraphBase Parent;
633
634  private:
635
636    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
637
638    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
639    ///
640    SmartGraph(const SmartGraph &) : ExtendedSmartGraphBase() {};
641
642    ///\brief Assignment of SmartGraph to another one is \e not allowed.
643    ///Use GraphCopy() instead.
644
645    ///Assignment of SmartGraph to another one is \e not allowed.
646    ///Use GraphCopy() instead.
647    void operator=(const SmartGraph &) {}
648
649  public:
650
651    /// Constructor
652
653    /// Constructor.
654    ///
655    SmartGraph() {}
656
657    ///Add a new node to the graph.
658
659    /// Add a new node to the graph.
660    /// \return The new node.
661    Node addNode() { return Parent::addNode(); }
662
663    ///Add a new edge to the graph.
664
665    ///Add a new edge to the graph with node \c s
666    ///and \c t.
667    ///\return The new edge.
668    Edge addEdge(const Node& s, const Node& t) {
669      return Parent::addEdge(s, t);
670    }
671
672    /// \brief Node validity check
673    ///
674    /// This function gives back true if the given node is valid,
675    /// ie. it is a real node of the graph.
676    ///
677    /// \warning A removed node (using Snapshot) could become valid again
678    /// when new nodes are added to the graph.
679    bool valid(Node n) const { return Parent::valid(n); }
680
681    /// \brief Arc validity check
682    ///
683    /// This function gives back true if the given arc is valid,
684    /// ie. it is a real arc of the graph.
685    ///
686    /// \warning A removed arc (using Snapshot) could become valid again
687    /// when new edges are added to the graph.
688    bool valid(Arc a) const { return Parent::valid(a); }
689
690    /// \brief Edge validity check
691    ///
692    /// This function gives back true if the given edge is valid,
693    /// ie. it is a real edge of the graph.
694    ///
695    /// \warning A removed edge (using Snapshot) could become valid again
696    /// when new edges are added to the graph.
697    bool valid(Edge e) const { return Parent::valid(e); }
698
699    ///Clear the graph.
700
701    ///Erase all the nodes and edges from the graph.
702    ///
703    void clear() {
704      Parent::clear();
705    }
706
707  public:
708
709    class Snapshot;
710
711  protected:
712
713    void saveSnapshot(Snapshot &s)
714    {
715      s._graph = this;
716      s.node_num = nodes.size();
717      s.arc_num = arcs.size();
718    }
719
720    void restoreSnapshot(const Snapshot &s)
721    {
722      while(s.arc_num<arcs.size()) {
723        int n=arcs.size()-1;
724        Edge arc=edgeFromId(n/2);
725        Parent::notifier(Edge()).erase(arc);
726        std::vector<Arc> dir;
727        dir.push_back(arcFromId(n));
728        dir.push_back(arcFromId(n-1));
729        Parent::notifier(Arc()).erase(dir);
730        nodes[arcs[n-1].target].first_out=arcs[n].next_out;
731        nodes[arcs[n].target].first_out=arcs[n-1].next_out;
732        arcs.pop_back();
733        arcs.pop_back();
734      }
735      while(s.node_num<nodes.size()) {
736        int n=nodes.size()-1;
737        Node node = nodeFromId(n);
738        Parent::notifier(Node()).erase(node);
739        nodes.pop_back();
740      }
741    }
742
743  public:
744
745    ///Class to make a snapshot of the digraph and to restrore to it later.
746
747    ///Class to make a snapshot of the digraph and to restrore to it later.
748    ///
749    ///The newly added nodes and arcs can be removed using the
750    ///restore() function.
751    ///
752    ///\note After you restore a state, you cannot restore
753    ///a later state, in other word you cannot add again the arcs deleted
754    ///by restore() using another one Snapshot instance.
755    ///
756    ///\warning If you do not use correctly the snapshot that can cause
757    ///either broken program, invalid state of the digraph, valid but
758    ///not the restored digraph or no change. Because the runtime performance
759    ///the validity of the snapshot is not stored.
760    class Snapshot
761    {
762      SmartGraph *_graph;
763    protected:
764      friend class SmartGraph;
765      unsigned int node_num;
766      unsigned int arc_num;
767    public:
768      ///Default constructor.
769
770      ///Default constructor.
771      ///To actually make a snapshot you must call save().
772      ///
773      Snapshot() : _graph(0) {}
774      ///Constructor that immediately makes a snapshot
775
776      ///This constructor immediately makes a snapshot of the digraph.
777      ///\param graph The digraph we make a snapshot of.
778      Snapshot(SmartGraph &graph) {
779        graph.saveSnapshot(*this);
780      }
781
782      ///Make a snapshot.
783
784      ///Make a snapshot of the graph.
785      ///
786      ///This function can be called more than once. In case of a repeated
787      ///call, the previous snapshot gets lost.
788      ///\param graph The digraph we make the snapshot of.
789      void save(SmartGraph &graph)
790      {
791        graph.saveSnapshot(*this);
792      }
793
794      ///Undo the changes until a snapshot.
795
796      ///Undo the changes until a snapshot created by save().
797      ///
798      ///\note After you restored a state, you cannot restore
799      ///a later state, in other word you cannot add again the arcs deleted
800      ///by restore().
801      void restore()
802      {
803        _graph->restoreSnapshot(*this);
804      }
805    };
806  };
807
808} //namespace lemon
809
810
811#endif //LEMON_SMART_GRAPH_H
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