COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/smart_graph.h @ 736:2e20aad15754

Last change on this file since 736:2e20aad15754 was 736:2e20aad15754, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Add reserve functions to ListGraph? and SmartGraph? (#311)
ListDigraph? and SmartDigraph? already have such functions.

File size: 22.0 KB
RevLine 
[209]1/* -*- mode: C++; indent-tabs-mode: nil; -*-
[109]2 *
[209]3 * This file is a part of LEMON, a generic C++ optimization library.
[109]4 *
[440]5 * Copyright (C) 2003-2009
[109]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
[220]28#include <lemon/core.h>
[109]29#include <lemon/error.h>
30#include <lemon/bits/graph_extender.h>
31
32namespace lemon {
33
34  class SmartDigraph;
35
36  class SmartDigraphBase {
37  protected:
38
[209]39    struct NodeT
[109]40    {
[209]41      int first_in, first_out;
[109]42      NodeT() {}
43    };
[209]44    struct ArcT
[109]45    {
[209]46      int target, source, next_in, next_out;
47      ArcT() {}
[109]48    };
49
50    std::vector<NodeT> nodes;
51    std::vector<ArcT> arcs;
[209]52
[109]53  public:
54
[617]55    typedef SmartDigraphBase Digraph;
[109]56
57    class Node;
58    class Arc;
59
60  public:
61
62    SmartDigraphBase() : nodes(), arcs() { }
[209]63    SmartDigraphBase(const SmartDigraphBase &_g)
[109]64      : nodes(_g.nodes), arcs(_g.arcs) { }
[209]65
[109]66    typedef True NodeNumTag;
[360]67    typedef True ArcNumTag;
[109]68
69    int nodeNum() const { return nodes.size(); }
70    int arcNum() const { return arcs.size(); }
71
72    int maxNodeId() const { return nodes.size()-1; }
73    int maxArcId() const { return arcs.size()-1; }
74
75    Node addNode() {
[209]76      int n = nodes.size();
[109]77      nodes.push_back(NodeT());
78      nodes[n].first_in = -1;
79      nodes[n].first_out = -1;
80      return Node(n);
81    }
[209]82
[109]83    Arc addArc(Node u, Node v) {
[209]84      int n = arcs.size();
[109]85      arcs.push_back(ArcT());
[209]86      arcs[n].source = u._id;
[109]87      arcs[n].target = v._id;
88      arcs[n].next_out = nodes[u._id].first_out;
89      arcs[n].next_in = nodes[v._id].first_in;
90      nodes[u._id].first_out = nodes[v._id].first_in = n;
91
92      return Arc(n);
93    }
94
95    void clear() {
96      arcs.clear();
97      nodes.clear();
98    }
99
100    Node source(Arc a) const { return Node(arcs[a._id].source); }
101    Node target(Arc a) const { return Node(arcs[a._id].target); }
102
103    static int id(Node v) { return v._id; }
104    static int id(Arc a) { return a._id; }
105
106    static Node nodeFromId(int id) { return Node(id);}
107    static Arc arcFromId(int id) { return Arc(id);}
108
[209]109    bool valid(Node n) const {
110      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
[149]111    }
[209]112    bool valid(Arc a) const {
113      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
[149]114    }
115
[109]116    class Node {
117      friend class SmartDigraphBase;
118      friend class SmartDigraph;
119
120    protected:
121      int _id;
122      explicit Node(int id) : _id(id) {}
123    public:
124      Node() {}
125      Node (Invalid) : _id(-1) {}
126      bool operator==(const Node i) const {return _id == i._id;}
127      bool operator!=(const Node i) const {return _id != i._id;}
128      bool operator<(const Node i) const {return _id < i._id;}
129    };
[209]130
[109]131
132    class Arc {
133      friend class SmartDigraphBase;
134      friend class SmartDigraph;
135
136    protected:
137      int _id;
138      explicit Arc(int id) : _id(id) {}
139    public:
140      Arc() { }
141      Arc (Invalid) : _id(-1) {}
142      bool operator==(const Arc i) const {return _id == i._id;}
143      bool operator!=(const Arc i) const {return _id != i._id;}
144      bool operator<(const Arc i) const {return _id < i._id;}
145    };
146
147    void first(Node& node) const {
148      node._id = nodes.size() - 1;
149    }
150
151    static void next(Node& node) {
152      --node._id;
153    }
154
155    void first(Arc& arc) const {
156      arc._id = arcs.size() - 1;
157    }
158
159    static void next(Arc& arc) {
160      --arc._id;
161    }
162
163    void firstOut(Arc& arc, const Node& node) const {
164      arc._id = nodes[node._id].first_out;
165    }
166
167    void nextOut(Arc& arc) const {
168      arc._id = arcs[arc._id].next_out;
169    }
170
171    void firstIn(Arc& arc, const Node& node) const {
172      arc._id = nodes[node._id].first_in;
173    }
[209]174
[109]175    void nextIn(Arc& arc) const {
176      arc._id = arcs[arc._id].next_in;
177    }
178
179  };
180
181  typedef DigraphExtender<SmartDigraphBase> ExtendedSmartDigraphBase;
182
183  ///\ingroup graphs
184  ///
185  ///\brief A smart directed graph class.
186  ///
[735]187  ///\ref SmartDigraph is a simple and fast digraph implementation.
188  ///It is also quite memory efficient but at the price
189  ///that it does not support node and arc deletion
190  ///(except for the Snapshot feature).
[109]191  ///
[735]192  ///This type fully conforms to the \ref concepts::Digraph "Digraph concept"
193  ///and it also provides some additional functionalities.
194  ///Most of its member functions and nested classes are documented
195  ///only in the concept class.
196  ///
197  ///\sa concepts::Digraph
198  ///\sa SmartGraph
[109]199  class SmartDigraph : public ExtendedSmartDigraphBase {
200    typedef ExtendedSmartDigraphBase Parent;
201
202  private:
[735]203    /// Digraphs are \e not copy constructible. Use DigraphCopy instead.
[109]204    SmartDigraph(const SmartDigraph &) : ExtendedSmartDigraphBase() {};
[735]205    /// \brief Assignment of a digraph to another one is \e not allowed.
206    /// Use DigraphCopy instead.
[109]207    void operator=(const SmartDigraph &) {}
208
209  public:
[209]210
[109]211    /// Constructor
[209]212
[109]213    /// Constructor.
214    ///
215    SmartDigraph() {};
[209]216
[109]217    ///Add a new node to the digraph.
[209]218
[735]219    ///This function adds a new node to the digraph.
220    ///\return The new node.
[109]221    Node addNode() { return Parent::addNode(); }
[209]222
[109]223    ///Add a new arc to the digraph.
[209]224
[735]225    ///This function adds a new arc to the digraph with source node \c s
[109]226    ///and target node \c t.
[559]227    ///\return The new arc.
[735]228    Arc addArc(Node s, Node t) {
[209]229      return Parent::addArc(s, t);
[109]230    }
231
[149]232    /// \brief Node validity check
233    ///
[735]234    /// This function gives back \c true if the given node is valid,
235    /// i.e. it is a real node of the digraph.
[149]236    ///
237    /// \warning A removed node (using Snapshot) could become valid again
[735]238    /// if new nodes are added to the digraph.
[149]239    bool valid(Node n) const { return Parent::valid(n); }
240
241    /// \brief Arc validity check
242    ///
[735]243    /// This function gives back \c true if the given arc is valid,
244    /// i.e. it is a real arc of the digraph.
[149]245    ///
246    /// \warning A removed arc (using Snapshot) could become valid again
[735]247    /// if new arcs are added to the graph.
[149]248    bool valid(Arc a) const { return Parent::valid(a); }
249
[109]250    ///Split a node.
[209]251
[735]252    ///This function splits the given node. First, a new node is added
253    ///to the digraph, then the source of each outgoing arc of node \c n
254    ///is moved to this new node.
255    ///If the second parameter \c connect is \c true (this is the default
256    ///value), then a new arc from node \c n to the newly created node
257    ///is also added.
[109]258    ///\return The newly created node.
259    ///
[735]260    ///\note All iterators remain valid.
261    ///
[109]262    ///\warning This functionality cannot be used together with the Snapshot
263    ///feature.
264    Node split(Node n, bool connect = true)
265    {
266      Node b = addNode();
267      nodes[b._id].first_out=nodes[n._id].first_out;
268      nodes[n._id].first_out=-1;
[370]269      for(int i=nodes[b._id].first_out; i!=-1; i=arcs[i].next_out) {
270        arcs[i].source=b._id;
271      }
[109]272      if(connect) addArc(n,b);
273      return b;
274    }
275
[735]276    ///Clear the digraph.
277
278    ///This function erases all nodes and arcs from the digraph.
279    ///
280    void clear() {
281      Parent::clear();
282    }
283
284    /// Reserve memory for nodes.
285
286    /// Using this function, it is possible to avoid superfluous memory
287    /// allocation: if you know that the digraph you want to build will
288    /// be large (e.g. it will contain millions of nodes and/or arcs),
289    /// then it is worth reserving space for this amount before starting
290    /// to build the digraph.
291    /// \sa reserveArc()
292    void reserveNode(int n) { nodes.reserve(n); };
293
294    /// Reserve memory for arcs.
295
296    /// Using this function, it is possible to avoid superfluous memory
297    /// allocation: if you know that the digraph you want to build will
298    /// be large (e.g. it will contain millions of nodes and/or arcs),
299    /// then it is worth reserving space for this amount before starting
300    /// to build the digraph.
301    /// \sa reserveNode()
302    void reserveArc(int m) { arcs.reserve(m); };
303
[109]304  public:
[209]305
[109]306    class Snapshot;
307
308  protected:
309
310    void restoreSnapshot(const Snapshot &s)
311    {
312      while(s.arc_num<arcs.size()) {
313        Arc arc = arcFromId(arcs.size()-1);
[209]314        Parent::notifier(Arc()).erase(arc);
315        nodes[arcs.back().source].first_out=arcs.back().next_out;
316        nodes[arcs.back().target].first_in=arcs.back().next_in;
317        arcs.pop_back();
[109]318      }
319      while(s.node_num<nodes.size()) {
320        Node node = nodeFromId(nodes.size()-1);
[209]321        Parent::notifier(Node()).erase(node);
322        nodes.pop_back();
[109]323      }
[209]324    }
[109]325
326  public:
327
[735]328    ///Class to make a snapshot of the digraph and to restore it later.
[109]329
[735]330    ///Class to make a snapshot of the digraph and to restore it later.
[109]331    ///
332    ///The newly added nodes and arcs can be removed using the
[735]333    ///restore() function. This is the only way for deleting nodes and/or
334    ///arcs from a SmartDigraph structure.
[109]335    ///
[735]336    ///\note After a state is restored, you cannot restore a later state,
337    ///i.e. you cannot add the removed nodes and arcs again using
338    ///another Snapshot instance.
339    ///
340    ///\warning Node splitting cannot be restored.
341    ///\warning The validity of the snapshot is not stored due to
342    ///performance reasons. If you do not use the snapshot correctly,
343    ///it can cause broken program, invalid or not restored state of
344    ///the digraph or no change.
[209]345    class Snapshot
[109]346    {
347      SmartDigraph *_graph;
348    protected:
349      friend class SmartDigraph;
350      unsigned int node_num;
351      unsigned int arc_num;
352    public:
353      ///Default constructor.
[209]354
[109]355      ///Default constructor.
[735]356      ///You have to call save() to actually make a snapshot.
[109]357      Snapshot() : _graph(0) {}
358      ///Constructor that immediately makes a snapshot
[209]359
[735]360      ///This constructor immediately makes a snapshot of the given digraph.
361      ///
362      Snapshot(SmartDigraph &gr) : _graph(&gr) {
[209]363        node_num=_graph->nodes.size();
364        arc_num=_graph->arcs.size();
[109]365      }
366
367      ///Make a snapshot.
368
[735]369      ///This function makes a snapshot of the given digraph.
370      ///It can be called more than once. In case of a repeated
[109]371      ///call, the previous snapshot gets lost.
[735]372      void save(SmartDigraph &gr) {
373        _graph=&gr;
[209]374        node_num=_graph->nodes.size();
375        arc_num=_graph->arcs.size();
[109]376      }
377
378      ///Undo the changes until a snapshot.
[209]379
[735]380      ///This function undos the changes until the last snapshot
381      ///created by save() or Snapshot(SmartDigraph&).
[109]382      void restore()
383      {
[209]384        _graph->restoreSnapshot(*this);
[109]385      }
386    };
387  };
388
389
390  class SmartGraphBase {
391
392  protected:
393
394    struct NodeT {
395      int first_out;
396    };
[209]397
[109]398    struct ArcT {
399      int target;
400      int next_out;
401    };
402
403    std::vector<NodeT> nodes;
404    std::vector<ArcT> arcs;
405
406    int first_free_arc;
[209]407
[109]408  public:
[209]409
[617]410    typedef SmartGraphBase Graph;
[109]411
412    class Node;
413    class Arc;
414    class Edge;
[209]415
[109]416    class Node {
417      friend class SmartGraphBase;
418    protected:
419
420      int _id;
421      explicit Node(int id) { _id = id;}
422
423    public:
424      Node() {}
425      Node (Invalid) { _id = -1; }
426      bool operator==(const Node& node) const {return _id == node._id;}
427      bool operator!=(const Node& node) const {return _id != node._id;}
428      bool operator<(const Node& node) const {return _id < node._id;}
429    };
430
431    class Edge {
432      friend class SmartGraphBase;
433    protected:
434
435      int _id;
436      explicit Edge(int id) { _id = id;}
437
438    public:
439      Edge() {}
440      Edge (Invalid) { _id = -1; }
441      bool operator==(const Edge& arc) const {return _id == arc._id;}
442      bool operator!=(const Edge& arc) const {return _id != arc._id;}
443      bool operator<(const Edge& arc) const {return _id < arc._id;}
444    };
445
446    class Arc {
447      friend class SmartGraphBase;
448    protected:
449
450      int _id;
451      explicit Arc(int id) { _id = id;}
452
453    public:
[329]454      operator Edge() const {
455        return _id != -1 ? edgeFromId(_id / 2) : INVALID;
[238]456      }
[109]457
458      Arc() {}
459      Arc (Invalid) { _id = -1; }
460      bool operator==(const Arc& arc) const {return _id == arc._id;}
461      bool operator!=(const Arc& arc) const {return _id != arc._id;}
462      bool operator<(const Arc& arc) const {return _id < arc._id;}
463    };
464
465
466
467    SmartGraphBase()
468      : nodes(), arcs() {}
469
[368]470    typedef True NodeNumTag;
471    typedef True EdgeNumTag;
472    typedef True ArcNumTag;
473
474    int nodeNum() const { return nodes.size(); }
475    int edgeNum() const { return arcs.size() / 2; }
476    int arcNum() const { return arcs.size(); }
[209]477
478    int maxNodeId() const { return nodes.size()-1; }
[109]479    int maxEdgeId() const { return arcs.size() / 2 - 1; }
480    int maxArcId() const { return arcs.size()-1; }
481
482    Node source(Arc e) const { return Node(arcs[e._id ^ 1].target); }
483    Node target(Arc e) const { return Node(arcs[e._id].target); }
484
[125]485    Node u(Edge e) const { return Node(arcs[2 * e._id].target); }
486    Node v(Edge e) const { return Node(arcs[2 * e._id + 1].target); }
[109]487
488    static bool direction(Arc e) {
489      return (e._id & 1) == 1;
490    }
491
492    static Arc direct(Edge e, bool d) {
493      return Arc(e._id * 2 + (d ? 1 : 0));
494    }
495
[209]496    void first(Node& node) const {
[109]497      node._id = nodes.size() - 1;
498    }
499
500    void next(Node& node) const {
501      --node._id;
502    }
503
[209]504    void first(Arc& arc) const {
[109]505      arc._id = arcs.size() - 1;
506    }
507
508    void next(Arc& arc) const {
509      --arc._id;
510    }
511
[209]512    void first(Edge& arc) const {
[109]513      arc._id = arcs.size() / 2 - 1;
514    }
515
516    void next(Edge& arc) const {
517      --arc._id;
518    }
519
520    void firstOut(Arc &arc, const Node& v) const {
521      arc._id = nodes[v._id].first_out;
522    }
523    void nextOut(Arc &arc) const {
524      arc._id = arcs[arc._id].next_out;
525    }
526
527    void firstIn(Arc &arc, const Node& v) const {
528      arc._id = ((nodes[v._id].first_out) ^ 1);
529      if (arc._id == -2) arc._id = -1;
530    }
531    void nextIn(Arc &arc) const {
532      arc._id = ((arcs[arc._id ^ 1].next_out) ^ 1);
533      if (arc._id == -2) arc._id = -1;
534    }
535
536    void firstInc(Edge &arc, bool& d, const Node& v) const {
537      int de = nodes[v._id].first_out;
538      if (de != -1) {
539        arc._id = de / 2;
540        d = ((de & 1) == 1);
541      } else {
542        arc._id = -1;
543        d = true;
544      }
545    }
546    void nextInc(Edge &arc, bool& d) const {
547      int de = (arcs[(arc._id * 2) | (d ? 1 : 0)].next_out);
548      if (de != -1) {
549        arc._id = de / 2;
550        d = ((de & 1) == 1);
551      } else {
552        arc._id = -1;
[209]553        d = true;
[109]554      }
555    }
[209]556
[109]557    static int id(Node v) { return v._id; }
558    static int id(Arc e) { return e._id; }
559    static int id(Edge e) { return e._id; }
560
561    static Node nodeFromId(int id) { return Node(id);}
562    static Arc arcFromId(int id) { return Arc(id);}
563    static Edge edgeFromId(int id) { return Edge(id);}
564
[209]565    bool valid(Node n) const {
566      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
[149]567    }
[209]568    bool valid(Arc a) const {
[149]569      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
570    }
[209]571    bool valid(Edge e) const {
572      return e._id >= 0 && 2 * e._id < static_cast<int>(arcs.size());
[149]573    }
574
[209]575    Node addNode() {
[109]576      int n = nodes.size();
577      nodes.push_back(NodeT());
578      nodes[n].first_out = -1;
[209]579
[109]580      return Node(n);
581    }
[209]582
[138]583    Edge addEdge(Node u, Node v) {
[109]584      int n = arcs.size();
585      arcs.push_back(ArcT());
586      arcs.push_back(ArcT());
[209]587
[109]588      arcs[n].target = u._id;
589      arcs[n | 1].target = v._id;
590
591      arcs[n].next_out = nodes[v._id].first_out;
592      nodes[v._id].first_out = n;
593
[209]594      arcs[n | 1].next_out = nodes[u._id].first_out;
[109]595      nodes[u._id].first_out = (n | 1);
596
597      return Edge(n / 2);
598    }
[209]599
[109]600    void clear() {
601      arcs.clear();
602      nodes.clear();
603    }
604
605  };
606
607  typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;
608
609  /// \ingroup graphs
610  ///
611  /// \brief A smart undirected graph class.
612  ///
[735]613  /// \ref SmartGraph is a simple and fast graph implementation.
614  /// It is also quite memory efficient but at the price
615  /// that it does not support node and edge deletion
616  /// (except for the Snapshot feature).
[109]617  ///
[735]618  /// This type fully conforms to the \ref concepts::Graph "Graph concept"
619  /// and it also provides some additional functionalities.
620  /// Most of its member functions and nested classes are documented
621  /// only in the concept class.
622  ///
623  /// \sa concepts::Graph
624  /// \sa SmartDigraph
[109]625  class SmartGraph : public ExtendedSmartGraphBase {
[617]626    typedef ExtendedSmartGraphBase Parent;
627
[109]628  private:
[735]629    /// Graphs are \e not copy constructible. Use GraphCopy instead.
[109]630    SmartGraph(const SmartGraph &) : ExtendedSmartGraphBase() {};
[735]631    /// \brief Assignment of a graph to another one is \e not allowed.
632    /// Use GraphCopy instead.
[109]633    void operator=(const SmartGraph &) {}
634
635  public:
636
637    /// Constructor
[209]638
[109]639    /// Constructor.
640    ///
641    SmartGraph() {}
642
[735]643    /// \brief Add a new node to the graph.
644    ///
645    /// This function adds a new node to the graph.
[559]646    /// \return The new node.
[109]647    Node addNode() { return Parent::addNode(); }
[209]648
[735]649    /// \brief Add a new edge to the graph.
650    ///
651    /// This function adds a new edge to the graph between nodes
652    /// \c u and \c v with inherent orientation from node \c u to
653    /// node \c v.
654    /// \return The new edge.
655    Edge addEdge(Node u, Node v) {
656      return Parent::addEdge(u, v);
[109]657    }
658
[149]659    /// \brief Node validity check
660    ///
[735]661    /// This function gives back \c true if the given node is valid,
662    /// i.e. it is a real node of the graph.
[149]663    ///
664    /// \warning A removed node (using Snapshot) could become valid again
[735]665    /// if new nodes are added to the graph.
[149]666    bool valid(Node n) const { return Parent::valid(n); }
667
[735]668    /// \brief Edge validity check
669    ///
670    /// This function gives back \c true if the given edge is valid,
671    /// i.e. it is a real edge of the graph.
672    ///
673    /// \warning A removed edge (using Snapshot) could become valid again
674    /// if new edges are added to the graph.
675    bool valid(Edge e) const { return Parent::valid(e); }
676
[149]677    /// \brief Arc validity check
678    ///
[735]679    /// This function gives back \c true if the given arc is valid,
680    /// i.e. it is a real arc of the graph.
[149]681    ///
682    /// \warning A removed arc (using Snapshot) could become valid again
[735]683    /// if new edges are added to the graph.
[149]684    bool valid(Arc a) const { return Parent::valid(a); }
685
[109]686    ///Clear the graph.
[209]687
[735]688    ///This function erases all nodes and arcs from the graph.
[109]689    ///
690    void clear() {
691      Parent::clear();
692    }
693
[736]694    /// Reserve memory for nodes.
695
696    /// Using this function, it is possible to avoid superfluous memory
697    /// allocation: if you know that the graph you want to build will
698    /// be large (e.g. it will contain millions of nodes and/or edges),
699    /// then it is worth reserving space for this amount before starting
700    /// to build the graph.
701    /// \sa reserveEdge()
702    void reserveNode(int n) { nodes.reserve(n); };
703
704    /// Reserve memory for edges.
705
706    /// Using this function, it is possible to avoid superfluous memory
707    /// allocation: if you know that the graph you want to build will
708    /// be large (e.g. it will contain millions of nodes and/or edges),
709    /// then it is worth reserving space for this amount before starting
710    /// to build the graph.
711    /// \sa reserveNode()
712    void reserveEdge(int m) { arcs.reserve(2 * m); };
713
[109]714  public:
[209]715
[109]716    class Snapshot;
717
718  protected:
719
720    void saveSnapshot(Snapshot &s)
721    {
722      s._graph = this;
723      s.node_num = nodes.size();
724      s.arc_num = arcs.size();
725    }
726
727    void restoreSnapshot(const Snapshot &s)
728    {
729      while(s.arc_num<arcs.size()) {
730        int n=arcs.size()-1;
731        Edge arc=edgeFromId(n/2);
[209]732        Parent::notifier(Edge()).erase(arc);
[109]733        std::vector<Arc> dir;
734        dir.push_back(arcFromId(n));
735        dir.push_back(arcFromId(n-1));
[209]736        Parent::notifier(Arc()).erase(dir);
[373]737        nodes[arcs[n-1].target].first_out=arcs[n].next_out;
738        nodes[arcs[n].target].first_out=arcs[n-1].next_out;
[209]739        arcs.pop_back();
740        arcs.pop_back();
[109]741      }
742      while(s.node_num<nodes.size()) {
743        int n=nodes.size()-1;
744        Node node = nodeFromId(n);
[209]745        Parent::notifier(Node()).erase(node);
746        nodes.pop_back();
[109]747      }
[209]748    }
[109]749
750  public:
751
[735]752    ///Class to make a snapshot of the graph and to restore it later.
[109]753
[735]754    ///Class to make a snapshot of the graph and to restore it later.
[109]755    ///
[735]756    ///The newly added nodes and edges can be removed using the
757    ///restore() function. This is the only way for deleting nodes and/or
758    ///edges from a SmartGraph structure.
[109]759    ///
[735]760    ///\note After a state is restored, you cannot restore a later state,
761    ///i.e. you cannot add the removed nodes and edges again using
762    ///another Snapshot instance.
[109]763    ///
[735]764    ///\warning The validity of the snapshot is not stored due to
765    ///performance reasons. If you do not use the snapshot correctly,
766    ///it can cause broken program, invalid or not restored state of
767    ///the graph or no change.
[209]768    class Snapshot
[109]769    {
770      SmartGraph *_graph;
771    protected:
772      friend class SmartGraph;
773      unsigned int node_num;
774      unsigned int arc_num;
775    public:
776      ///Default constructor.
[209]777
[109]778      ///Default constructor.
[735]779      ///You have to call save() to actually make a snapshot.
[109]780      Snapshot() : _graph(0) {}
781      ///Constructor that immediately makes a snapshot
[209]782
[735]783      /// This constructor immediately makes a snapshot of the given graph.
784      ///
785      Snapshot(SmartGraph &gr) {
786        gr.saveSnapshot(*this);
[109]787      }
788
789      ///Make a snapshot.
790
[735]791      ///This function makes a snapshot of the given graph.
792      ///It can be called more than once. In case of a repeated
[109]793      ///call, the previous snapshot gets lost.
[735]794      void save(SmartGraph &gr)
[109]795      {
[735]796        gr.saveSnapshot(*this);
[109]797      }
798
[735]799      ///Undo the changes until the last snapshot.
[209]800
[735]801      ///This function undos the changes until the last snapshot
802      ///created by save() or Snapshot(SmartGraph&).
[109]803      void restore()
804      {
805        _graph->restoreSnapshot(*this);
806      }
807    };
808  };
[209]809
[109]810} //namespace lemon
811
812
813#endif //LEMON_SMART_GRAPH_H
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