COIN-OR::LEMON - Graph Library

source: lemon-1.0/lemon/list_graph.h @ 233:28239207a8a3

Last change on this file since 233:28239207a8a3 was 220:a5d8c039f218, checked in by Balazs Dezso <deba@…>, 11 years ago

Reorganize header files (Ticket #97)

In addition on some places the DefaultMap?<G, K, V> is replaced with
ItemSetTraits?<G, K>::template Map<V>::Type, to decrease the dependencies
of different tools. It is obviously better solution.

File size: 42.5 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) 2003-2008
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_LIST_GRAPH_H
20#define LEMON_LIST_GRAPH_H
21
22///\ingroup graphs
23///\file
24///\brief ListDigraph, ListGraph classes.
25
26#include <lemon/core.h>
27#include <lemon/error.h>
28#include <lemon/bits/graph_extender.h>
29
30#include <vector>
31#include <list>
32
33namespace lemon {
34
35  class ListDigraphBase {
36
37  protected:
38    struct NodeT {
39      int first_in, first_out;
40      int prev, next;
41    };
42
43    struct ArcT {
44      int target, source;
45      int prev_in, prev_out;
46      int next_in, next_out;
47    };
48
49    std::vector<NodeT> nodes;
50
51    int first_node;
52
53    int first_free_node;
54
55    std::vector<ArcT> arcs;
56
57    int first_free_arc;
58
59  public:
60
61    typedef ListDigraphBase Digraph;
62
63    class Node {
64      friend class ListDigraphBase;
65    protected:
66
67      int id;
68      explicit Node(int pid) { id = pid;}
69
70    public:
71      Node() {}
72      Node (Invalid) { id = -1; }
73      bool operator==(const Node& node) const {return id == node.id;}
74      bool operator!=(const Node& node) const {return id != node.id;}
75      bool operator<(const Node& node) const {return id < node.id;}
76    };
77
78    class Arc {
79      friend class ListDigraphBase;
80    protected:
81
82      int id;
83      explicit Arc(int pid) { id = pid;}
84
85    public:
86      Arc() {}
87      Arc (Invalid) { id = -1; }
88      bool operator==(const Arc& arc) const {return id == arc.id;}
89      bool operator!=(const Arc& arc) const {return id != arc.id;}
90      bool operator<(const Arc& arc) const {return id < arc.id;}
91    };
92
93
94
95    ListDigraphBase()
96      : nodes(), first_node(-1),
97        first_free_node(-1), arcs(), first_free_arc(-1) {}
98
99
100    int maxNodeId() const { return nodes.size()-1; }
101    int maxArcId() const { return arcs.size()-1; }
102
103    Node source(Arc e) const { return Node(arcs[e.id].source); }
104    Node target(Arc e) const { return Node(arcs[e.id].target); }
105
106
107    void first(Node& node) const {
108      node.id = first_node;
109    }
110
111    void next(Node& node) const {
112      node.id = nodes[node.id].next;
113    }
114
115
116    void first(Arc& arc) const {
117      int n;
118      for(n = first_node;
119          n!=-1 && nodes[n].first_in == -1;
120          n = nodes[n].next) {}
121      arc.id = (n == -1) ? -1 : nodes[n].first_in;
122    }
123
124    void next(Arc& arc) const {
125      if (arcs[arc.id].next_in != -1) {
126        arc.id = arcs[arc.id].next_in;
127      } else {
128        int n;
129        for(n = nodes[arcs[arc.id].target].next;
130            n!=-1 && nodes[n].first_in == -1;
131            n = nodes[n].next) {}
132        arc.id = (n == -1) ? -1 : nodes[n].first_in;
133      }
134    }
135
136    void firstOut(Arc &e, const Node& v) const {
137      e.id = nodes[v.id].first_out;
138    }
139    void nextOut(Arc &e) const {
140      e.id=arcs[e.id].next_out;
141    }
142
143    void firstIn(Arc &e, const Node& v) const {
144      e.id = nodes[v.id].first_in;
145    }
146    void nextIn(Arc &e) const {
147      e.id=arcs[e.id].next_in;
148    }
149
150
151    static int id(Node v) { return v.id; }
152    static int id(Arc e) { return e.id; }
153
154    static Node nodeFromId(int id) { return Node(id);}
155    static Arc arcFromId(int id) { return Arc(id);}
156
157    bool valid(Node n) const {
158      return n.id >= 0 && n.id < static_cast<int>(nodes.size()) &&
159        nodes[n.id].prev != -2;
160    }
161
162    bool valid(Arc a) const {
163      return a.id >= 0 && a.id < static_cast<int>(arcs.size()) &&
164        arcs[a.id].prev_in != -2;
165    }
166
167    Node addNode() {
168      int n;
169
170      if(first_free_node==-1) {
171        n = nodes.size();
172        nodes.push_back(NodeT());
173      } else {
174        n = first_free_node;
175        first_free_node = nodes[n].next;
176      }
177
178      nodes[n].next = first_node;
179      if(first_node != -1) nodes[first_node].prev = n;
180      first_node = n;
181      nodes[n].prev = -1;
182
183      nodes[n].first_in = nodes[n].first_out = -1;
184
185      return Node(n);
186    }
187
188    Arc addArc(Node u, Node v) {
189      int n;
190
191      if (first_free_arc == -1) {
192        n = arcs.size();
193        arcs.push_back(ArcT());
194      } else {
195        n = first_free_arc;
196        first_free_arc = arcs[n].next_in;
197      }
198
199      arcs[n].source = u.id;
200      arcs[n].target = v.id;
201
202      arcs[n].next_out = nodes[u.id].first_out;
203      if(nodes[u.id].first_out != -1) {
204        arcs[nodes[u.id].first_out].prev_out = n;
205      }
206
207      arcs[n].next_in = nodes[v.id].first_in;
208      if(nodes[v.id].first_in != -1) {
209        arcs[nodes[v.id].first_in].prev_in = n;
210      }
211
212      arcs[n].prev_in = arcs[n].prev_out = -1;
213
214      nodes[u.id].first_out = nodes[v.id].first_in = n;
215
216      return Arc(n);
217    }
218
219    void erase(const Node& node) {
220      int n = node.id;
221
222      if(nodes[n].next != -1) {
223        nodes[nodes[n].next].prev = nodes[n].prev;
224      }
225
226      if(nodes[n].prev != -1) {
227        nodes[nodes[n].prev].next = nodes[n].next;
228      } else {
229        first_node = nodes[n].next;
230      }
231
232      nodes[n].next = first_free_node;
233      first_free_node = n;
234      nodes[n].prev = -2;
235
236    }
237
238    void erase(const Arc& arc) {
239      int n = arc.id;
240
241      if(arcs[n].next_in!=-1) {
242        arcs[arcs[n].next_in].prev_in = arcs[n].prev_in;
243      }
244
245      if(arcs[n].prev_in!=-1) {
246        arcs[arcs[n].prev_in].next_in = arcs[n].next_in;
247      } else {
248        nodes[arcs[n].target].first_in = arcs[n].next_in;
249      }
250
251
252      if(arcs[n].next_out!=-1) {
253        arcs[arcs[n].next_out].prev_out = arcs[n].prev_out;
254      }
255
256      if(arcs[n].prev_out!=-1) {
257        arcs[arcs[n].prev_out].next_out = arcs[n].next_out;
258      } else {
259        nodes[arcs[n].source].first_out = arcs[n].next_out;
260      }
261
262      arcs[n].next_in = first_free_arc;
263      first_free_arc = n;
264      arcs[n].prev_in = -2;
265    }
266
267    void clear() {
268      arcs.clear();
269      nodes.clear();
270      first_node = first_free_node = first_free_arc = -1;
271    }
272
273  protected:
274    void changeTarget(Arc e, Node n)
275    {
276      if(arcs[e.id].next_in != -1)
277        arcs[arcs[e.id].next_in].prev_in = arcs[e.id].prev_in;
278      if(arcs[e.id].prev_in != -1)
279        arcs[arcs[e.id].prev_in].next_in = arcs[e.id].next_in;
280      else nodes[arcs[e.id].target].first_in = arcs[e.id].next_in;
281      if (nodes[n.id].first_in != -1) {
282        arcs[nodes[n.id].first_in].prev_in = e.id;
283      }
284      arcs[e.id].target = n.id;
285      arcs[e.id].prev_in = -1;
286      arcs[e.id].next_in = nodes[n.id].first_in;
287      nodes[n.id].first_in = e.id;
288    }
289    void changeSource(Arc e, Node n)
290    {
291      if(arcs[e.id].next_out != -1)
292        arcs[arcs[e.id].next_out].prev_out = arcs[e.id].prev_out;
293      if(arcs[e.id].prev_out != -1)
294        arcs[arcs[e.id].prev_out].next_out = arcs[e.id].next_out;
295      else nodes[arcs[e.id].source].first_out = arcs[e.id].next_out;
296      if (nodes[n.id].first_out != -1) {
297        arcs[nodes[n.id].first_out].prev_out = e.id;
298      }
299      arcs[e.id].source = n.id;
300      arcs[e.id].prev_out = -1;
301      arcs[e.id].next_out = nodes[n.id].first_out;
302      nodes[n.id].first_out = e.id;
303    }
304
305  };
306
307  typedef DigraphExtender<ListDigraphBase> ExtendedListDigraphBase;
308
309  /// \addtogroup graphs
310  /// @{
311
312  ///A general directed graph structure.
313
314  ///\ref ListDigraph is a simple and fast <em>directed graph</em>
315  ///implementation based on static linked lists that are stored in
316  ///\c std::vector structures.
317  ///
318  ///It conforms to the \ref concepts::Digraph "Digraph concept" and it
319  ///also provides several useful additional functionalities.
320  ///Most of the member functions and nested classes are documented
321  ///only in the concept class.
322  ///
323  ///An important extra feature of this digraph implementation is that
324  ///its maps are real \ref concepts::ReferenceMap "reference map"s.
325  ///
326  ///\sa concepts::Digraph
327
328  class ListDigraph : public ExtendedListDigraphBase {
329  private:
330    ///ListDigraph is \e not copy constructible. Use copyDigraph() instead.
331
332    ///ListDigraph is \e not copy constructible. Use copyDigraph() instead.
333    ///
334    ListDigraph(const ListDigraph &) :ExtendedListDigraphBase() {};
335    ///\brief Assignment of ListDigraph to another one is \e not allowed.
336    ///Use copyDigraph() instead.
337
338    ///Assignment of ListDigraph to another one is \e not allowed.
339    ///Use copyDigraph() instead.
340    void operator=(const ListDigraph &) {}
341  public:
342
343    typedef ExtendedListDigraphBase Parent;
344
345    /// Constructor
346
347    /// Constructor.
348    ///
349    ListDigraph() {}
350
351    ///Add a new node to the digraph.
352
353    ///Add a new node to the digraph.
354    ///\return the new node.
355    Node addNode() { return Parent::addNode(); }
356
357    ///Add a new arc to the digraph.
358
359    ///Add a new arc to the digraph with source node \c s
360    ///and target node \c t.
361    ///\return the new arc.
362    Arc addArc(const Node& s, const Node& t) {
363      return Parent::addArc(s, t);
364    }
365
366    /// Node validity check
367
368    /// This function gives back true if the given node is valid,
369    /// ie. it is a real node of the graph.
370    ///
371    /// \warning A Node pointing to a removed item
372    /// could become valid again later if new nodes are
373    /// added to the graph.
374    bool valid(Node n) const { return Parent::valid(n); }
375
376    /// Arc validity check
377
378    /// This function gives back true if the given arc is valid,
379    /// ie. it is a real arc of the graph.
380    ///
381    /// \warning An Arc pointing to a removed item
382    /// could become valid again later if new nodes are
383    /// added to the graph.
384    bool valid(Arc a) const { return Parent::valid(a); }
385
386    /// Change the target of \c e to \c n
387
388    /// Change the target of \c e to \c n
389    ///
390    ///\note The <tt>ArcIt</tt>s and <tt>OutArcIt</tt>s referencing
391    ///the changed arc remain valid. However <tt>InArcIt</tt>s are
392    ///invalidated.
393    ///
394    ///\warning This functionality cannot be used together with the Snapshot
395    ///feature.
396    void changeTarget(Arc e, Node n) {
397      Parent::changeTarget(e,n);
398    }
399    /// Change the source of \c e to \c n
400
401    /// Change the source of \c e to \c n
402    ///
403    ///\note The <tt>ArcIt</tt>s and <tt>InArcIt</tt>s referencing
404    ///the changed arc remain valid. However <tt>OutArcIt</tt>s are
405    ///invalidated.
406    ///
407    ///\warning This functionality cannot be used together with the Snapshot
408    ///feature.
409    void changeSource(Arc e, Node n) {
410      Parent::changeSource(e,n);
411    }
412
413    /// Invert the direction of an arc.
414
415    ///\note The <tt>ArcIt</tt>s referencing the changed arc remain
416    ///valid. However <tt>OutArcIt</tt>s and <tt>InArcIt</tt>s are
417    ///invalidated.
418    ///
419    ///\warning This functionality cannot be used together with the Snapshot
420    ///feature.
421    void reverseArc(Arc e) {
422      Node t=target(e);
423      changeTarget(e,source(e));
424      changeSource(e,t);
425    }
426
427    /// Reserve memory for nodes.
428
429    /// Using this function it is possible to avoid the superfluous memory
430    /// allocation: if you know that the digraph you want to build will
431    /// be very large (e.g. it will contain millions of nodes and/or arcs)
432    /// then it is worth reserving space for this amount before starting
433    /// to build the digraph.
434    /// \sa reserveArc
435    void reserveNode(int n) { nodes.reserve(n); };
436
437    /// Reserve memory for arcs.
438
439    /// Using this function it is possible to avoid the superfluous memory
440    /// allocation: if you know that the digraph you want to build will
441    /// be very large (e.g. it will contain millions of nodes and/or arcs)
442    /// then it is worth reserving space for this amount before starting
443    /// to build the digraph.
444    /// \sa reserveNode
445    void reserveArc(int m) { arcs.reserve(m); };
446
447    ///Contract two nodes.
448
449    ///This function contracts two nodes.
450    ///Node \p b will be removed but instead of deleting
451    ///incident arcs, they will be joined to \p a.
452    ///The last parameter \p r controls whether to remove loops. \c true
453    ///means that loops will be removed.
454    ///
455    ///\note The <tt>ArcIt</tt>s referencing a moved arc remain
456    ///valid. However <tt>InArcIt</tt>s and <tt>OutArcIt</tt>s
457    ///may be invalidated.
458    ///
459    ///\warning This functionality cannot be used together with the Snapshot
460    ///feature.
461    void contract(Node a, Node b, bool r = true)
462    {
463      for(OutArcIt e(*this,b);e!=INVALID;) {
464        OutArcIt f=e;
465        ++f;
466        if(r && target(e)==a) erase(e);
467        else changeSource(e,a);
468        e=f;
469      }
470      for(InArcIt e(*this,b);e!=INVALID;) {
471        InArcIt f=e;
472        ++f;
473        if(r && source(e)==a) erase(e);
474        else changeTarget(e,a);
475        e=f;
476      }
477      erase(b);
478    }
479
480    ///Split a node.
481
482    ///This function splits a node. First a new node is added to the digraph,
483    ///then the source of each outgoing arc of \c n is moved to this new node.
484    ///If \c connect is \c true (this is the default value), then a new arc
485    ///from \c n to the newly created node is also added.
486    ///\return The newly created node.
487    ///
488    ///\note The <tt>ArcIt</tt>s referencing a moved arc remain
489    ///valid. However <tt>InArcIt</tt>s and <tt>OutArcIt</tt>s may
490    ///be invalidated.
491    ///
492    ///\warning This functionality cannot be used together with the
493    ///Snapshot feature.
494    ///
495    ///\todo It could be implemented in a bit faster way.
496    Node split(Node n, bool connect = true) {
497      Node b = addNode();
498      for(OutArcIt e(*this,n);e!=INVALID;) {
499        OutArcIt f=e;
500        ++f;
501        changeSource(e,b);
502        e=f;
503      }
504      if (connect) addArc(n,b);
505      return b;
506    }
507
508    ///Split an arc.
509
510    ///This function splits an arc. First a new node \c b is added to
511    ///the digraph, then the original arc is re-targeted to \c
512    ///b. Finally an arc from \c b to the original target is added.
513    ///
514    ///\return The newly created node.
515    ///
516    ///\warning This functionality cannot be used together with the
517    ///Snapshot feature.
518    Node split(Arc e) {
519      Node b = addNode();
520      addArc(b,target(e));
521      changeTarget(e,b);
522      return b;
523    }
524
525    /// \brief Class to make a snapshot of the digraph and restore
526    /// it later.
527    ///
528    /// Class to make a snapshot of the digraph and restore it later.
529    ///
530    /// The newly added nodes and arcs can be removed using the
531    /// restore() function.
532    ///
533    /// \warning Arc and node deletions and other modifications (e.g.
534    /// contracting, splitting, reversing arcs or nodes) cannot be
535    /// restored. These events invalidate the snapshot.
536    class Snapshot {
537    protected:
538
539      typedef Parent::NodeNotifier NodeNotifier;
540
541      class NodeObserverProxy : public NodeNotifier::ObserverBase {
542      public:
543
544        NodeObserverProxy(Snapshot& _snapshot)
545          : snapshot(_snapshot) {}
546
547        using NodeNotifier::ObserverBase::attach;
548        using NodeNotifier::ObserverBase::detach;
549        using NodeNotifier::ObserverBase::attached;
550
551      protected:
552
553        virtual void add(const Node& node) {
554          snapshot.addNode(node);
555        }
556        virtual void add(const std::vector<Node>& nodes) {
557          for (int i = nodes.size() - 1; i >= 0; ++i) {
558            snapshot.addNode(nodes[i]);
559          }
560        }
561        virtual void erase(const Node& node) {
562          snapshot.eraseNode(node);
563        }
564        virtual void erase(const std::vector<Node>& nodes) {
565          for (int i = 0; i < int(nodes.size()); ++i) {
566            snapshot.eraseNode(nodes[i]);
567          }
568        }
569        virtual void build() {
570          Node node;
571          std::vector<Node> nodes;
572          for (notifier()->first(node); node != INVALID;
573               notifier()->next(node)) {
574            nodes.push_back(node);
575          }
576          for (int i = nodes.size() - 1; i >= 0; --i) {
577            snapshot.addNode(nodes[i]);
578          }
579        }
580        virtual void clear() {
581          Node node;
582          for (notifier()->first(node); node != INVALID;
583               notifier()->next(node)) {
584            snapshot.eraseNode(node);
585          }
586        }
587
588        Snapshot& snapshot;
589      };
590
591      class ArcObserverProxy : public ArcNotifier::ObserverBase {
592      public:
593
594        ArcObserverProxy(Snapshot& _snapshot)
595          : snapshot(_snapshot) {}
596
597        using ArcNotifier::ObserverBase::attach;
598        using ArcNotifier::ObserverBase::detach;
599        using ArcNotifier::ObserverBase::attached;
600
601      protected:
602
603        virtual void add(const Arc& arc) {
604          snapshot.addArc(arc);
605        }
606        virtual void add(const std::vector<Arc>& arcs) {
607          for (int i = arcs.size() - 1; i >= 0; ++i) {
608            snapshot.addArc(arcs[i]);
609          }
610        }
611        virtual void erase(const Arc& arc) {
612          snapshot.eraseArc(arc);
613        }
614        virtual void erase(const std::vector<Arc>& arcs) {
615          for (int i = 0; i < int(arcs.size()); ++i) {
616            snapshot.eraseArc(arcs[i]);
617          }
618        }
619        virtual void build() {
620          Arc arc;
621          std::vector<Arc> arcs;
622          for (notifier()->first(arc); arc != INVALID;
623               notifier()->next(arc)) {
624            arcs.push_back(arc);
625          }
626          for (int i = arcs.size() - 1; i >= 0; --i) {
627            snapshot.addArc(arcs[i]);
628          }
629        }
630        virtual void clear() {
631          Arc arc;
632          for (notifier()->first(arc); arc != INVALID;
633               notifier()->next(arc)) {
634            snapshot.eraseArc(arc);
635          }
636        }
637
638        Snapshot& snapshot;
639      };
640
641      ListDigraph *digraph;
642
643      NodeObserverProxy node_observer_proxy;
644      ArcObserverProxy arc_observer_proxy;
645
646      std::list<Node> added_nodes;
647      std::list<Arc> added_arcs;
648
649
650      void addNode(const Node& node) {
651        added_nodes.push_front(node);
652      }
653      void eraseNode(const Node& node) {
654        std::list<Node>::iterator it =
655          std::find(added_nodes.begin(), added_nodes.end(), node);
656        if (it == added_nodes.end()) {
657          clear();
658          arc_observer_proxy.detach();
659          throw NodeNotifier::ImmediateDetach();
660        } else {
661          added_nodes.erase(it);
662        }
663      }
664
665      void addArc(const Arc& arc) {
666        added_arcs.push_front(arc);
667      }
668      void eraseArc(const Arc& arc) {
669        std::list<Arc>::iterator it =
670          std::find(added_arcs.begin(), added_arcs.end(), arc);
671        if (it == added_arcs.end()) {
672          clear();
673          node_observer_proxy.detach();
674          throw ArcNotifier::ImmediateDetach();
675        } else {
676          added_arcs.erase(it);
677        }
678      }
679
680      void attach(ListDigraph &_digraph) {
681        digraph = &_digraph;
682        node_observer_proxy.attach(digraph->notifier(Node()));
683        arc_observer_proxy.attach(digraph->notifier(Arc()));
684      }
685
686      void detach() {
687        node_observer_proxy.detach();
688        arc_observer_proxy.detach();
689      }
690
691      bool attached() const {
692        return node_observer_proxy.attached();
693      }
694
695      void clear() {
696        added_nodes.clear();
697        added_arcs.clear();
698      }
699
700    public:
701
702      /// \brief Default constructor.
703      ///
704      /// Default constructor.
705      /// To actually make a snapshot you must call save().
706      Snapshot()
707        : digraph(0), node_observer_proxy(*this),
708          arc_observer_proxy(*this) {}
709
710      /// \brief Constructor that immediately makes a snapshot.
711      ///
712      /// This constructor immediately makes a snapshot of the digraph.
713      /// \param _digraph The digraph we make a snapshot of.
714      Snapshot(ListDigraph &_digraph)
715        : node_observer_proxy(*this),
716          arc_observer_proxy(*this) {
717        attach(_digraph);
718      }
719
720      /// \brief Make a snapshot.
721      ///
722      /// Make a snapshot of the digraph.
723      ///
724      /// This function can be called more than once. In case of a repeated
725      /// call, the previous snapshot gets lost.
726      /// \param _digraph The digraph we make the snapshot of.
727      void save(ListDigraph &_digraph) {
728        if (attached()) {
729          detach();
730          clear();
731        }
732        attach(_digraph);
733      }
734
735      /// \brief Undo the changes until the last snapshot.
736      //
737      /// Undo the changes until the last snapshot created by save().
738      void restore() {
739        detach();
740        for(std::list<Arc>::iterator it = added_arcs.begin();
741            it != added_arcs.end(); ++it) {
742          digraph->erase(*it);
743        }
744        for(std::list<Node>::iterator it = added_nodes.begin();
745            it != added_nodes.end(); ++it) {
746          digraph->erase(*it);
747        }
748        clear();
749      }
750
751      /// \brief Gives back true when the snapshot is valid.
752      ///
753      /// Gives back true when the snapshot is valid.
754      bool valid() const {
755        return attached();
756      }
757    };
758
759  };
760
761  ///@}
762
763  class ListGraphBase {
764
765  protected:
766
767    struct NodeT {
768      int first_out;
769      int prev, next;
770    };
771
772    struct ArcT {
773      int target;
774      int prev_out, next_out;
775    };
776
777    std::vector<NodeT> nodes;
778
779    int first_node;
780
781    int first_free_node;
782
783    std::vector<ArcT> arcs;
784
785    int first_free_arc;
786
787  public:
788
789    typedef ListGraphBase Digraph;
790
791    class Node;
792    class Arc;
793    class Edge;
794
795    class Node {
796      friend class ListGraphBase;
797    protected:
798
799      int id;
800      explicit Node(int pid) { id = pid;}
801
802    public:
803      Node() {}
804      Node (Invalid) { id = -1; }
805      bool operator==(const Node& node) const {return id == node.id;}
806      bool operator!=(const Node& node) const {return id != node.id;}
807      bool operator<(const Node& node) const {return id < node.id;}
808    };
809
810    class Edge {
811      friend class ListGraphBase;
812    protected:
813
814      int id;
815      explicit Edge(int pid) { id = pid;}
816
817    public:
818      Edge() {}
819      Edge (Invalid) { id = -1; }
820      bool operator==(const Edge& edge) const {return id == edge.id;}
821      bool operator!=(const Edge& edge) const {return id != edge.id;}
822      bool operator<(const Edge& edge) const {return id < edge.id;}
823    };
824
825    class Arc {
826      friend class ListGraphBase;
827    protected:
828
829      int id;
830      explicit Arc(int pid) { id = pid;}
831
832    public:
833      operator Edge() const { return edgeFromId(id / 2); }
834
835      Arc() {}
836      Arc (Invalid) { id = -1; }
837      bool operator==(const Arc& arc) const {return id == arc.id;}
838      bool operator!=(const Arc& arc) const {return id != arc.id;}
839      bool operator<(const Arc& arc) const {return id < arc.id;}
840    };
841
842
843
844    ListGraphBase()
845      : nodes(), first_node(-1),
846        first_free_node(-1), arcs(), first_free_arc(-1) {}
847
848
849    int maxNodeId() const { return nodes.size()-1; }
850    int maxEdgeId() const { return arcs.size() / 2 - 1; }
851    int maxArcId() const { return arcs.size()-1; }
852
853    Node source(Arc e) const { return Node(arcs[e.id ^ 1].target); }
854    Node target(Arc e) const { return Node(arcs[e.id].target); }
855
856    Node u(Edge e) const { return Node(arcs[2 * e.id].target); }
857    Node v(Edge e) const { return Node(arcs[2 * e.id + 1].target); }
858
859    static bool direction(Arc e) {
860      return (e.id & 1) == 1;
861    }
862
863    static Arc direct(Edge e, bool d) {
864      return Arc(e.id * 2 + (d ? 1 : 0));
865    }
866
867    void first(Node& node) const {
868      node.id = first_node;
869    }
870
871    void next(Node& node) const {
872      node.id = nodes[node.id].next;
873    }
874
875    void first(Arc& e) const {
876      int n = first_node;
877      while (n != -1 && nodes[n].first_out == -1) {
878        n = nodes[n].next;
879      }
880      e.id = (n == -1) ? -1 : nodes[n].first_out;
881    }
882
883    void next(Arc& e) const {
884      if (arcs[e.id].next_out != -1) {
885        e.id = arcs[e.id].next_out;
886      } else {
887        int n = nodes[arcs[e.id ^ 1].target].next;
888        while(n != -1 && nodes[n].first_out == -1) {
889          n = nodes[n].next;
890        }
891        e.id = (n == -1) ? -1 : nodes[n].first_out;
892      }
893    }
894
895    void first(Edge& e) const {
896      int n = first_node;
897      while (n != -1) {
898        e.id = nodes[n].first_out;
899        while ((e.id & 1) != 1) {
900          e.id = arcs[e.id].next_out;
901        }
902        if (e.id != -1) {
903          e.id /= 2;
904          return;
905        }
906        n = nodes[n].next;
907      }
908      e.id = -1;
909    }
910
911    void next(Edge& e) const {
912      int n = arcs[e.id * 2].target;
913      e.id = arcs[(e.id * 2) | 1].next_out;
914      while ((e.id & 1) != 1) {
915        e.id = arcs[e.id].next_out;
916      }
917      if (e.id != -1) {
918        e.id /= 2;
919        return;
920      }
921      n = nodes[n].next;
922      while (n != -1) {
923        e.id = nodes[n].first_out;
924        while ((e.id & 1) != 1) {
925          e.id = arcs[e.id].next_out;
926        }
927        if (e.id != -1) {
928          e.id /= 2;
929          return;
930        }
931        n = nodes[n].next;
932      }
933      e.id = -1;
934    }
935
936    void firstOut(Arc &e, const Node& v) const {
937      e.id = nodes[v.id].first_out;
938    }
939    void nextOut(Arc &e) const {
940      e.id = arcs[e.id].next_out;
941    }
942
943    void firstIn(Arc &e, const Node& v) const {
944      e.id = ((nodes[v.id].first_out) ^ 1);
945      if (e.id == -2) e.id = -1;
946    }
947    void nextIn(Arc &e) const {
948      e.id = ((arcs[e.id ^ 1].next_out) ^ 1);
949      if (e.id == -2) e.id = -1;
950    }
951
952    void firstInc(Edge &e, bool& d, const Node& v) const {
953      int a = nodes[v.id].first_out;
954      if (a != -1 ) {
955        e.id = a / 2;
956        d = ((a & 1) == 1);
957      } else {
958        e.id = -1;
959        d = true;
960      }
961    }
962    void nextInc(Edge &e, bool& d) const {
963      int a = (arcs[(e.id * 2) | (d ? 1 : 0)].next_out);
964      if (a != -1 ) {
965        e.id = a / 2;
966        d = ((a & 1) == 1);
967      } else {
968        e.id = -1;
969        d = true;
970      }
971    }
972
973    static int id(Node v) { return v.id; }
974    static int id(Arc e) { return e.id; }
975    static int id(Edge e) { return e.id; }
976
977    static Node nodeFromId(int id) { return Node(id);}
978    static Arc arcFromId(int id) { return Arc(id);}
979    static Edge edgeFromId(int id) { return Edge(id);}
980
981    bool valid(Node n) const {
982      return n.id >= 0 && n.id < static_cast<int>(nodes.size()) &&
983        nodes[n.id].prev != -2;
984    }
985
986    bool valid(Arc a) const {
987      return a.id >= 0 && a.id < static_cast<int>(arcs.size()) &&
988        arcs[a.id].prev_out != -2;
989    }
990
991    bool valid(Edge e) const {
992      return e.id >= 0 && 2 * e.id < static_cast<int>(arcs.size()) &&
993        arcs[2 * e.id].prev_out != -2;
994    }
995
996    Node addNode() {
997      int n;
998
999      if(first_free_node==-1) {
1000        n = nodes.size();
1001        nodes.push_back(NodeT());
1002      } else {
1003        n = first_free_node;
1004        first_free_node = nodes[n].next;
1005      }
1006
1007      nodes[n].next = first_node;
1008      if (first_node != -1) nodes[first_node].prev = n;
1009      first_node = n;
1010      nodes[n].prev = -1;
1011
1012      nodes[n].first_out = -1;
1013
1014      return Node(n);
1015    }
1016
1017    Edge addEdge(Node u, Node v) {
1018      int n;
1019
1020      if (first_free_arc == -1) {
1021        n = arcs.size();
1022        arcs.push_back(ArcT());
1023        arcs.push_back(ArcT());
1024      } else {
1025        n = first_free_arc;
1026        first_free_arc = arcs[n].next_out;
1027      }
1028
1029      arcs[n].target = u.id;
1030      arcs[n | 1].target = v.id;
1031
1032      arcs[n].next_out = nodes[v.id].first_out;
1033      if (nodes[v.id].first_out != -1) {
1034        arcs[nodes[v.id].first_out].prev_out = n;
1035      }
1036      arcs[n].prev_out = -1;
1037      nodes[v.id].first_out = n;
1038
1039      arcs[n | 1].next_out = nodes[u.id].first_out;
1040      if (nodes[u.id].first_out != -1) {
1041        arcs[nodes[u.id].first_out].prev_out = (n | 1);
1042      }
1043      arcs[n | 1].prev_out = -1;
1044      nodes[u.id].first_out = (n | 1);
1045
1046      return Edge(n / 2);
1047    }
1048
1049    void erase(const Node& node) {
1050      int n = node.id;
1051
1052      if(nodes[n].next != -1) {
1053        nodes[nodes[n].next].prev = nodes[n].prev;
1054      }
1055
1056      if(nodes[n].prev != -1) {
1057        nodes[nodes[n].prev].next = nodes[n].next;
1058      } else {
1059        first_node = nodes[n].next;
1060      }
1061
1062      nodes[n].next = first_free_node;
1063      first_free_node = n;
1064      nodes[n].prev = -2;
1065    }
1066
1067    void erase(const Edge& edge) {
1068      int n = edge.id * 2;
1069
1070      if (arcs[n].next_out != -1) {
1071        arcs[arcs[n].next_out].prev_out = arcs[n].prev_out;
1072      }
1073
1074      if (arcs[n].prev_out != -1) {
1075        arcs[arcs[n].prev_out].next_out = arcs[n].next_out;
1076      } else {
1077        nodes[arcs[n | 1].target].first_out = arcs[n].next_out;
1078      }
1079
1080      if (arcs[n | 1].next_out != -1) {
1081        arcs[arcs[n | 1].next_out].prev_out = arcs[n | 1].prev_out;
1082      }
1083
1084      if (arcs[n | 1].prev_out != -1) {
1085        arcs[arcs[n | 1].prev_out].next_out = arcs[n | 1].next_out;
1086      } else {
1087        nodes[arcs[n].target].first_out = arcs[n | 1].next_out;
1088      }
1089
1090      arcs[n].next_out = first_free_arc;
1091      first_free_arc = n;
1092      arcs[n].prev_out = -2;
1093      arcs[n | 1].prev_out = -2;
1094
1095    }
1096
1097    void clear() {
1098      arcs.clear();
1099      nodes.clear();
1100      first_node = first_free_node = first_free_arc = -1;
1101    }
1102
1103  protected:
1104
1105    void changeTarget(Edge e, Node n) {
1106      if(arcs[2 * e.id].next_out != -1) {
1107        arcs[arcs[2 * e.id].next_out].prev_out = arcs[2 * e.id].prev_out;
1108      }
1109      if(arcs[2 * e.id].prev_out != -1) {
1110        arcs[arcs[2 * e.id].prev_out].next_out =
1111          arcs[2 * e.id].next_out;
1112      } else {
1113        nodes[arcs[(2 * e.id) | 1].target].first_out =
1114          arcs[2 * e.id].next_out;
1115      }
1116
1117      if (nodes[n.id].first_out != -1) {
1118        arcs[nodes[n.id].first_out].prev_out = 2 * e.id;
1119      }
1120      arcs[(2 * e.id) | 1].target = n.id;
1121      arcs[2 * e.id].prev_out = -1;
1122      arcs[2 * e.id].next_out = nodes[n.id].first_out;
1123      nodes[n.id].first_out = 2 * e.id;
1124    }
1125
1126    void changeSource(Edge e, Node n) {
1127      if(arcs[(2 * e.id) | 1].next_out != -1) {
1128        arcs[arcs[(2 * e.id) | 1].next_out].prev_out =
1129          arcs[(2 * e.id) | 1].prev_out;
1130      }
1131      if(arcs[(2 * e.id) | 1].prev_out != -1) {
1132        arcs[arcs[(2 * e.id) | 1].prev_out].next_out =
1133          arcs[(2 * e.id) | 1].next_out;
1134      } else {
1135        nodes[arcs[2 * e.id].target].first_out =
1136          arcs[(2 * e.id) | 1].next_out;
1137      }
1138
1139      if (nodes[n.id].first_out != -1) {
1140        arcs[nodes[n.id].first_out].prev_out = ((2 * e.id) | 1);
1141      }
1142      arcs[2 * e.id].target = n.id;
1143      arcs[(2 * e.id) | 1].prev_out = -1;
1144      arcs[(2 * e.id) | 1].next_out = nodes[n.id].first_out;
1145      nodes[n.id].first_out = ((2 * e.id) | 1);
1146    }
1147
1148  };
1149
1150  typedef GraphExtender<ListGraphBase> ExtendedListGraphBase;
1151
1152
1153  /// \addtogroup graphs
1154  /// @{
1155
1156  ///A general undirected graph structure.
1157
1158  ///\ref ListGraph is a simple and fast <em>undirected graph</em>
1159  ///implementation based on static linked lists that are stored in
1160  ///\c std::vector structures.
1161  ///
1162  ///It conforms to the \ref concepts::Graph "Graph concept" and it
1163  ///also provides several useful additional functionalities.
1164  ///Most of the member functions and nested classes are documented
1165  ///only in the concept class.
1166  ///
1167  ///An important extra feature of this graph implementation is that
1168  ///its maps are real \ref concepts::ReferenceMap "reference map"s.
1169  ///
1170  ///\sa concepts::Graph
1171
1172  class ListGraph : public ExtendedListGraphBase {
1173  private:
1174    ///ListGraph is \e not copy constructible. Use copyGraph() instead.
1175
1176    ///ListGraph is \e not copy constructible. Use copyGraph() instead.
1177    ///
1178    ListGraph(const ListGraph &) :ExtendedListGraphBase()  {};
1179    ///\brief Assignment of ListGraph to another one is \e not allowed.
1180    ///Use copyGraph() instead.
1181
1182    ///Assignment of ListGraph to another one is \e not allowed.
1183    ///Use copyGraph() instead.
1184    void operator=(const ListGraph &) {}
1185  public:
1186    /// Constructor
1187
1188    /// Constructor.
1189    ///
1190    ListGraph() {}
1191
1192    typedef ExtendedListGraphBase Parent;
1193
1194    typedef Parent::OutArcIt IncEdgeIt;
1195
1196    /// \brief Add a new node to the graph.
1197    ///
1198    /// Add a new node to the graph.
1199    /// \return the new node.
1200    Node addNode() { return Parent::addNode(); }
1201
1202    /// \brief Add a new edge to the graph.
1203    ///
1204    /// Add a new edge to the graph with source node \c s
1205    /// and target node \c t.
1206    /// \return the new edge.
1207    Edge addEdge(const Node& s, const Node& t) {
1208      return Parent::addEdge(s, t);
1209    }
1210    /// Node validity check
1211
1212    /// This function gives back true if the given node is valid,
1213    /// ie. it is a real node of the graph.
1214    ///
1215    /// \warning A Node pointing to a removed item
1216    /// could become valid again later if new nodes are
1217    /// added to the graph.
1218    bool valid(Node n) const { return Parent::valid(n); }
1219    /// Arc validity check
1220
1221    /// This function gives back true if the given arc is valid,
1222    /// ie. it is a real arc of the graph.
1223    ///
1224    /// \warning An Arc pointing to a removed item
1225    /// could become valid again later if new edges are
1226    /// added to the graph.
1227    bool valid(Arc a) const { return Parent::valid(a); }
1228    /// Edge validity check
1229
1230    /// This function gives back true if the given edge is valid,
1231    /// ie. it is a real arc of the graph.
1232    ///
1233    /// \warning A Edge pointing to a removed item
1234    /// could become valid again later if new edges are
1235    /// added to the graph.
1236    bool valid(Edge e) const { return Parent::valid(e); }
1237    /// \brief Change the source of \c e to \c n
1238    ///
1239    /// This function changes the source of \c e to \c n.
1240    ///
1241    ///\note The <tt>ArcIt</tt>s and <tt>InArcIt</tt>s
1242    ///referencing the changed arc remain
1243    ///valid. However <tt>OutArcIt</tt>s are invalidated.
1244    ///
1245    ///\warning This functionality cannot be used together with the
1246    ///Snapshot feature.
1247    void changeSource(Edge e, Node n) {
1248      Parent::changeSource(e,n);
1249    }
1250    /// \brief Change the target of \c e to \c n
1251    ///
1252    /// This function changes the target of \c e to \c n.
1253    ///
1254    /// \note The <tt>ArcIt</tt>s referencing the changed arc remain
1255    /// valid. However the other iterators may be invalidated.
1256    ///
1257    ///\warning This functionality cannot be used together with the
1258    ///Snapshot feature.
1259    void changeTarget(Edge e, Node n) {
1260      Parent::changeTarget(e,n);
1261    }
1262    /// \brief Change the source of \c e to \c n
1263    ///
1264    /// This function changes the source of \c e to \c n.
1265    /// It also changes the proper node of the represented edge.
1266    ///
1267    ///\note The <tt>ArcIt</tt>s and <tt>InArcIt</tt>s
1268    ///referencing the changed arc remain
1269    ///valid. However <tt>OutArcIt</tt>s are invalidated.
1270    ///
1271    ///\warning This functionality cannot be used together with the
1272    ///Snapshot feature.
1273    void changeSource(Arc e, Node n) {
1274      if (Parent::direction(e)) {
1275        Parent::changeSource(e,n);
1276      } else {
1277        Parent::changeTarget(e,n);
1278      }
1279    }
1280    /// \brief Change the target of \c e to \c n
1281    ///
1282    /// This function changes the target of \c e to \c n.
1283    /// It also changes the proper node of the represented edge.
1284    ///
1285    ///\note The <tt>ArcIt</tt>s and <tt>OutArcIt</tt>s
1286    ///referencing the changed arc remain
1287    ///valid. However <tt>InArcIt</tt>s are invalidated.
1288    ///
1289    ///\warning This functionality cannot be used together with the
1290    ///Snapshot feature.
1291    void changeTarget(Arc e, Node n) {
1292      if (Parent::direction(e)) {
1293        Parent::changeTarget(e,n);
1294      } else {
1295        Parent::changeSource(e,n);
1296      }
1297    }
1298    /// \brief Contract two nodes.
1299    ///
1300    /// This function contracts two nodes.
1301    /// Node \p b will be removed but instead of deleting
1302    /// its neighboring arcs, they will be joined to \p a.
1303    /// The last parameter \p r controls whether to remove loops. \c true
1304    /// means that loops will be removed.
1305    ///
1306    /// \note The <tt>ArcIt</tt>s referencing a moved arc remain
1307    /// valid.
1308    ///
1309    ///\warning This functionality cannot be used together with the
1310    ///Snapshot feature.
1311    void contract(Node a, Node b, bool r = true) {
1312      for(IncEdgeIt e(*this, b); e!=INVALID;) {
1313        IncEdgeIt f = e; ++f;
1314        if (r && runningNode(e) == a) {
1315          erase(e);
1316        } else if (source(e) == b) {
1317          changeSource(e, a);
1318        } else {
1319          changeTarget(e, a);
1320        }
1321        e = f;
1322      }
1323      erase(b);
1324    }
1325
1326
1327    /// \brief Class to make a snapshot of the graph and restore
1328    /// it later.
1329    ///
1330    /// Class to make a snapshot of the graph and restore it later.
1331    ///
1332    /// The newly added nodes and edges can be removed
1333    /// using the restore() function.
1334    ///
1335    /// \warning Edge and node deletions and other modifications
1336    /// (e.g. changing nodes of edges, contracting nodes) cannot be
1337    /// restored. These events invalidate the snapshot.
1338    class Snapshot {
1339    protected:
1340
1341      typedef Parent::NodeNotifier NodeNotifier;
1342
1343      class NodeObserverProxy : public NodeNotifier::ObserverBase {
1344      public:
1345
1346        NodeObserverProxy(Snapshot& _snapshot)
1347          : snapshot(_snapshot) {}
1348
1349        using NodeNotifier::ObserverBase::attach;
1350        using NodeNotifier::ObserverBase::detach;
1351        using NodeNotifier::ObserverBase::attached;
1352
1353      protected:
1354
1355        virtual void add(const Node& node) {
1356          snapshot.addNode(node);
1357        }
1358        virtual void add(const std::vector<Node>& nodes) {
1359          for (int i = nodes.size() - 1; i >= 0; ++i) {
1360            snapshot.addNode(nodes[i]);
1361          }
1362        }
1363        virtual void erase(const Node& node) {
1364          snapshot.eraseNode(node);
1365        }
1366        virtual void erase(const std::vector<Node>& nodes) {
1367          for (int i = 0; i < int(nodes.size()); ++i) {
1368            snapshot.eraseNode(nodes[i]);
1369          }
1370        }
1371        virtual void build() {
1372          Node node;
1373          std::vector<Node> nodes;
1374          for (notifier()->first(node); node != INVALID;
1375               notifier()->next(node)) {
1376            nodes.push_back(node);
1377          }
1378          for (int i = nodes.size() - 1; i >= 0; --i) {
1379            snapshot.addNode(nodes[i]);
1380          }
1381        }
1382        virtual void clear() {
1383          Node node;
1384          for (notifier()->first(node); node != INVALID;
1385               notifier()->next(node)) {
1386            snapshot.eraseNode(node);
1387          }
1388        }
1389
1390        Snapshot& snapshot;
1391      };
1392
1393      class EdgeObserverProxy : public EdgeNotifier::ObserverBase {
1394      public:
1395
1396        EdgeObserverProxy(Snapshot& _snapshot)
1397          : snapshot(_snapshot) {}
1398
1399        using EdgeNotifier::ObserverBase::attach;
1400        using EdgeNotifier::ObserverBase::detach;
1401        using EdgeNotifier::ObserverBase::attached;
1402
1403      protected:
1404
1405        virtual void add(const Edge& edge) {
1406          snapshot.addEdge(edge);
1407        }
1408        virtual void add(const std::vector<Edge>& edges) {
1409          for (int i = edges.size() - 1; i >= 0; ++i) {
1410            snapshot.addEdge(edges[i]);
1411          }
1412        }
1413        virtual void erase(const Edge& edge) {
1414          snapshot.eraseEdge(edge);
1415        }
1416        virtual void erase(const std::vector<Edge>& edges) {
1417          for (int i = 0; i < int(edges.size()); ++i) {
1418            snapshot.eraseEdge(edges[i]);
1419          }
1420        }
1421        virtual void build() {
1422          Edge edge;
1423          std::vector<Edge> edges;
1424          for (notifier()->first(edge); edge != INVALID;
1425               notifier()->next(edge)) {
1426            edges.push_back(edge);
1427          }
1428          for (int i = edges.size() - 1; i >= 0; --i) {
1429            snapshot.addEdge(edges[i]);
1430          }
1431        }
1432        virtual void clear() {
1433          Edge edge;
1434          for (notifier()->first(edge); edge != INVALID;
1435               notifier()->next(edge)) {
1436            snapshot.eraseEdge(edge);
1437          }
1438        }
1439
1440        Snapshot& snapshot;
1441      };
1442
1443      ListGraph *graph;
1444
1445      NodeObserverProxy node_observer_proxy;
1446      EdgeObserverProxy edge_observer_proxy;
1447
1448      std::list<Node> added_nodes;
1449      std::list<Edge> added_edges;
1450
1451
1452      void addNode(const Node& node) {
1453        added_nodes.push_front(node);
1454      }
1455      void eraseNode(const Node& node) {
1456        std::list<Node>::iterator it =
1457          std::find(added_nodes.begin(), added_nodes.end(), node);
1458        if (it == added_nodes.end()) {
1459          clear();
1460          edge_observer_proxy.detach();
1461          throw NodeNotifier::ImmediateDetach();
1462        } else {
1463          added_nodes.erase(it);
1464        }
1465      }
1466
1467      void addEdge(const Edge& edge) {
1468        added_edges.push_front(edge);
1469      }
1470      void eraseEdge(const Edge& edge) {
1471        std::list<Edge>::iterator it =
1472          std::find(added_edges.begin(), added_edges.end(), edge);
1473        if (it == added_edges.end()) {
1474          clear();
1475          node_observer_proxy.detach();
1476          throw EdgeNotifier::ImmediateDetach();
1477        } else {
1478          added_edges.erase(it);
1479        }
1480      }
1481
1482      void attach(ListGraph &_graph) {
1483        graph = &_graph;
1484        node_observer_proxy.attach(graph->notifier(Node()));
1485        edge_observer_proxy.attach(graph->notifier(Edge()));
1486      }
1487
1488      void detach() {
1489        node_observer_proxy.detach();
1490        edge_observer_proxy.detach();
1491      }
1492
1493      bool attached() const {
1494        return node_observer_proxy.attached();
1495      }
1496
1497      void clear() {
1498        added_nodes.clear();
1499        added_edges.clear();
1500      }
1501
1502    public:
1503
1504      /// \brief Default constructor.
1505      ///
1506      /// Default constructor.
1507      /// To actually make a snapshot you must call save().
1508      Snapshot()
1509        : graph(0), node_observer_proxy(*this),
1510          edge_observer_proxy(*this) {}
1511
1512      /// \brief Constructor that immediately makes a snapshot.
1513      ///
1514      /// This constructor immediately makes a snapshot of the graph.
1515      /// \param _graph The graph we make a snapshot of.
1516      Snapshot(ListGraph &_graph)
1517        : node_observer_proxy(*this),
1518          edge_observer_proxy(*this) {
1519        attach(_graph);
1520      }
1521
1522      /// \brief Make a snapshot.
1523      ///
1524      /// Make a snapshot of the graph.
1525      ///
1526      /// This function can be called more than once. In case of a repeated
1527      /// call, the previous snapshot gets lost.
1528      /// \param _graph The graph we make the snapshot of.
1529      void save(ListGraph &_graph) {
1530        if (attached()) {
1531          detach();
1532          clear();
1533        }
1534        attach(_graph);
1535      }
1536
1537      /// \brief Undo the changes until the last snapshot.
1538      //
1539      /// Undo the changes until the last snapshot created by save().
1540      void restore() {
1541        detach();
1542        for(std::list<Edge>::iterator it = added_edges.begin();
1543            it != added_edges.end(); ++it) {
1544          graph->erase(*it);
1545        }
1546        for(std::list<Node>::iterator it = added_nodes.begin();
1547            it != added_nodes.end(); ++it) {
1548          graph->erase(*it);
1549        }
1550        clear();
1551      }
1552
1553      /// \brief Gives back true when the snapshot is valid.
1554      ///
1555      /// Gives back true when the snapshot is valid.
1556      bool valid() const {
1557        return attached();
1558      }
1559    };
1560  };
1561
1562  /// @}
1563} //namespace lemon
1564
1565
1566#endif
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