lemon/smart_graph.h
changeset 784 1a7fe3bef514
parent 778 a143f19f465b
parent 736 2e20aad15754
child 787 c2230649a493
     1.1 --- a/lemon/smart_graph.h	Fri Oct 16 10:21:37 2009 +0200
     1.2 +++ b/lemon/smart_graph.h	Thu Nov 05 15:50:01 2009 +0100
     1.3 @@ -2,7 +2,7 @@
     1.4   *
     1.5   * This file is a part of LEMON, a generic C++ optimization library.
     1.6   *
     1.7 - * Copyright (C) 2003-2008
     1.8 + * Copyright (C) 2003-2009
     1.9   * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
    1.10   * (Egervary Research Group on Combinatorial Optimization, EGRES).
    1.11   *
    1.12 @@ -32,10 +32,7 @@
    1.13  namespace lemon {
    1.14  
    1.15    class SmartDigraph;
    1.16 -  ///Base of SmartDigraph
    1.17  
    1.18 -  ///Base of SmartDigraph
    1.19 -  ///
    1.20    class SmartDigraphBase {
    1.21    protected:
    1.22  
    1.23 @@ -55,7 +52,7 @@
    1.24  
    1.25    public:
    1.26  
    1.27 -    typedef SmartDigraphBase Graph;
    1.28 +    typedef SmartDigraphBase Digraph;
    1.29  
    1.30      class Node;
    1.31      class Arc;
    1.32 @@ -67,7 +64,7 @@
    1.33        : nodes(_g.nodes), arcs(_g.arcs) { }
    1.34  
    1.35      typedef True NodeNumTag;
    1.36 -    typedef True EdgeNumTag;
    1.37 +    typedef True ArcNumTag;
    1.38  
    1.39      int nodeNum() const { return nodes.size(); }
    1.40      int arcNum() const { return arcs.size(); }
    1.41 @@ -187,32 +184,26 @@
    1.42    ///
    1.43    ///\brief A smart directed graph class.
    1.44    ///
    1.45 -  ///This is a simple and fast digraph implementation.
    1.46 -  ///It is also quite memory efficient, but at the price
    1.47 -  ///that <b> it does support only limited (only stack-like)
    1.48 -  ///node and arc deletions</b>.
    1.49 -  ///It conforms to the \ref concepts::Digraph "Digraph concept" with
    1.50 -  ///an important extra feature that its maps are real \ref
    1.51 -  ///concepts::ReferenceMap "reference map"s.
    1.52 +  ///\ref SmartDigraph is a simple and fast digraph implementation.
    1.53 +  ///It is also quite memory efficient but at the price
    1.54 +  ///that it does not support node and arc deletion 
    1.55 +  ///(except for the Snapshot feature).
    1.56    ///
    1.57 -  ///\sa concepts::Digraph.
    1.58 +  ///This type fully conforms to the \ref concepts::Digraph "Digraph concept"
    1.59 +  ///and it also provides some additional functionalities.
    1.60 +  ///Most of its member functions and nested classes are documented
    1.61 +  ///only in the concept class.
    1.62 +  ///
    1.63 +  ///\sa concepts::Digraph
    1.64 +  ///\sa SmartGraph
    1.65    class SmartDigraph : public ExtendedSmartDigraphBase {
    1.66 -  public:
    1.67 -
    1.68      typedef ExtendedSmartDigraphBase Parent;
    1.69  
    1.70    private:
    1.71 -
    1.72 -    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
    1.73 -
    1.74 -    ///SmartDigraph is \e not copy constructible. Use DigraphCopy() instead.
    1.75 -    ///
    1.76 +    /// Digraphs are \e not copy constructible. Use DigraphCopy instead.
    1.77      SmartDigraph(const SmartDigraph &) : ExtendedSmartDigraphBase() {};
    1.78 -    ///\brief Assignment of SmartDigraph to another one is \e not allowed.
    1.79 -    ///Use DigraphCopy() instead.
    1.80 -
    1.81 -    ///Assignment of SmartDigraph to another one is \e not allowed.
    1.82 -    ///Use DigraphCopy() instead.
    1.83 +    /// \brief Assignment of a digraph to another one is \e not allowed.
    1.84 +    /// Use DigraphCopy instead.
    1.85      void operator=(const SmartDigraph &) {}
    1.86  
    1.87    public:
    1.88 @@ -225,79 +216,49 @@
    1.89  
    1.90      ///Add a new node to the digraph.
    1.91  
    1.92 -    /// \return the new node.
    1.93 -    ///
    1.94 +    ///This function adds a new node to the digraph.
    1.95 +    ///\return The new node.
    1.96      Node addNode() { return Parent::addNode(); }
    1.97  
    1.98      ///Add a new arc to the digraph.
    1.99  
   1.100 -    ///Add a new arc to the digraph with source node \c s
   1.101 +    ///This function adds a new arc to the digraph with source node \c s
   1.102      ///and target node \c t.
   1.103 -    ///\return the new arc.
   1.104 -    Arc addArc(const Node& s, const Node& t) {
   1.105 +    ///\return The new arc.
   1.106 +    Arc addArc(Node s, Node t) {
   1.107        return Parent::addArc(s, t);
   1.108      }
   1.109  
   1.110 -    /// \brief Using this it is possible to avoid the superfluous memory
   1.111 -    /// allocation.
   1.112 -
   1.113 -    /// Using this it is possible to avoid the superfluous memory
   1.114 -    /// allocation: if you know that the digraph you want to build will
   1.115 -    /// be very large (e.g. it will contain millions of nodes and/or arcs)
   1.116 -    /// then it is worth reserving space for this amount before starting
   1.117 -    /// to build the digraph.
   1.118 -    /// \sa reserveArc
   1.119 -    void reserveNode(int n) { nodes.reserve(n); };
   1.120 -
   1.121 -    /// \brief Using this it is possible to avoid the superfluous memory
   1.122 -    /// allocation.
   1.123 -
   1.124 -    /// Using this it is possible to avoid the superfluous memory
   1.125 -    /// allocation: if you know that the digraph you want to build will
   1.126 -    /// be very large (e.g. it will contain millions of nodes and/or arcs)
   1.127 -    /// then it is worth reserving space for this amount before starting
   1.128 -    /// to build the digraph.
   1.129 -    /// \sa reserveNode
   1.130 -    void reserveArc(int m) { arcs.reserve(m); };
   1.131 -
   1.132      /// \brief Node validity check
   1.133      ///
   1.134 -    /// This function gives back true if the given node is valid,
   1.135 -    /// ie. it is a real node of the graph.
   1.136 +    /// This function gives back \c true if the given node is valid,
   1.137 +    /// i.e. it is a real node of the digraph.
   1.138      ///
   1.139      /// \warning A removed node (using Snapshot) could become valid again
   1.140 -    /// when new nodes are added to the graph.
   1.141 +    /// if new nodes are added to the digraph.
   1.142      bool valid(Node n) const { return Parent::valid(n); }
   1.143  
   1.144      /// \brief Arc validity check
   1.145      ///
   1.146 -    /// This function gives back true if the given arc is valid,
   1.147 -    /// ie. it is a real arc of the graph.
   1.148 +    /// This function gives back \c true if the given arc is valid,
   1.149 +    /// i.e. it is a real arc of the digraph.
   1.150      ///
   1.151      /// \warning A removed arc (using Snapshot) could become valid again
   1.152 -    /// when new arcs are added to the graph.
   1.153 +    /// if new arcs are added to the graph.
   1.154      bool valid(Arc a) const { return Parent::valid(a); }
   1.155  
   1.156 -    ///Clear the digraph.
   1.157 -
   1.158 -    ///Erase all the nodes and arcs from the digraph.
   1.159 -    ///
   1.160 -    void clear() {
   1.161 -      Parent::clear();
   1.162 -    }
   1.163 -
   1.164      ///Split a node.
   1.165  
   1.166 -    ///This function splits a node. First a new node is added to the digraph,
   1.167 -    ///then the source of each outgoing arc of \c n is moved to this new node.
   1.168 -    ///If \c connect is \c true (this is the default value), then a new arc
   1.169 -    ///from \c n to the newly created node is also added.
   1.170 +    ///This function splits the given node. First, a new node is added
   1.171 +    ///to the digraph, then the source of each outgoing arc of node \c n
   1.172 +    ///is moved to this new node.
   1.173 +    ///If the second parameter \c connect is \c true (this is the default
   1.174 +    ///value), then a new arc from node \c n to the newly created node
   1.175 +    ///is also added.
   1.176      ///\return The newly created node.
   1.177      ///
   1.178 -    ///\note The <tt>Arc</tt>s
   1.179 -    ///referencing a moved arc remain
   1.180 -    ///valid. However <tt>InArc</tt>'s and <tt>OutArc</tt>'s
   1.181 -    ///may be invalidated.
   1.182 +    ///\note All iterators remain valid.
   1.183 +    ///
   1.184      ///\warning This functionality cannot be used together with the Snapshot
   1.185      ///feature.
   1.186      Node split(Node n, bool connect = true)
   1.187 @@ -305,11 +266,41 @@
   1.188        Node b = addNode();
   1.189        nodes[b._id].first_out=nodes[n._id].first_out;
   1.190        nodes[n._id].first_out=-1;
   1.191 -      for(int i=nodes[b._id].first_out;i!=-1;i++) arcs[i].source=b._id;
   1.192 +      for(int i=nodes[b._id].first_out; i!=-1; i=arcs[i].next_out) {
   1.193 +        arcs[i].source=b._id;
   1.194 +      }
   1.195        if(connect) addArc(n,b);
   1.196        return b;
   1.197      }
   1.198  
   1.199 +    ///Clear the digraph.
   1.200 +
   1.201 +    ///This function erases all nodes and arcs from the digraph.
   1.202 +    ///
   1.203 +    void clear() {
   1.204 +      Parent::clear();
   1.205 +    }
   1.206 +
   1.207 +    /// Reserve memory for nodes.
   1.208 +
   1.209 +    /// Using this function, it is possible to avoid superfluous memory
   1.210 +    /// allocation: if you know that the digraph you want to build will
   1.211 +    /// be large (e.g. it will contain millions of nodes and/or arcs),
   1.212 +    /// then it is worth reserving space for this amount before starting
   1.213 +    /// to build the digraph.
   1.214 +    /// \sa reserveArc()
   1.215 +    void reserveNode(int n) { nodes.reserve(n); };
   1.216 +
   1.217 +    /// Reserve memory for arcs.
   1.218 +
   1.219 +    /// Using this function, it is possible to avoid superfluous memory
   1.220 +    /// allocation: if you know that the digraph you want to build will
   1.221 +    /// be large (e.g. it will contain millions of nodes and/or arcs),
   1.222 +    /// then it is worth reserving space for this amount before starting
   1.223 +    /// to build the digraph.
   1.224 +    /// \sa reserveNode()
   1.225 +    void reserveArc(int m) { arcs.reserve(m); };
   1.226 +
   1.227    public:
   1.228  
   1.229      class Snapshot;
   1.230 @@ -334,20 +325,23 @@
   1.231  
   1.232    public:
   1.233  
   1.234 -    ///Class to make a snapshot of the digraph and to restrore to it later.
   1.235 +    ///Class to make a snapshot of the digraph and to restore it later.
   1.236  
   1.237 -    ///Class to make a snapshot of the digraph and to restrore to it later.
   1.238 +    ///Class to make a snapshot of the digraph and to restore it later.
   1.239      ///
   1.240      ///The newly added nodes and arcs can be removed using the
   1.241 -    ///restore() function.
   1.242 -    ///\note After you restore a state, you cannot restore
   1.243 -    ///a later state, in other word you cannot add again the arcs deleted
   1.244 -    ///by restore() using another one Snapshot instance.
   1.245 +    ///restore() function. This is the only way for deleting nodes and/or
   1.246 +    ///arcs from a SmartDigraph structure.
   1.247      ///
   1.248 -    ///\warning If you do not use correctly the snapshot that can cause
   1.249 -    ///either broken program, invalid state of the digraph, valid but
   1.250 -    ///not the restored digraph or no change. Because the runtime performance
   1.251 -    ///the validity of the snapshot is not stored.
   1.252 +    ///\note After a state is restored, you cannot restore a later state, 
   1.253 +    ///i.e. you cannot add the removed nodes and arcs again using
   1.254 +    ///another Snapshot instance.
   1.255 +    ///
   1.256 +    ///\warning Node splitting cannot be restored.
   1.257 +    ///\warning The validity of the snapshot is not stored due to
   1.258 +    ///performance reasons. If you do not use the snapshot correctly,
   1.259 +    ///it can cause broken program, invalid or not restored state of
   1.260 +    ///the digraph or no change.
   1.261      class Snapshot
   1.262      {
   1.263        SmartDigraph *_graph;
   1.264 @@ -359,39 +353,32 @@
   1.265        ///Default constructor.
   1.266  
   1.267        ///Default constructor.
   1.268 -      ///To actually make a snapshot you must call save().
   1.269 -      ///
   1.270 +      ///You have to call save() to actually make a snapshot.
   1.271        Snapshot() : _graph(0) {}
   1.272        ///Constructor that immediately makes a snapshot
   1.273  
   1.274 -      ///This constructor immediately makes a snapshot of the digraph.
   1.275 -      ///\param graph The digraph we make a snapshot of.
   1.276 -      Snapshot(SmartDigraph &graph) : _graph(&graph) {
   1.277 +      ///This constructor immediately makes a snapshot of the given digraph.
   1.278 +      ///
   1.279 +      Snapshot(SmartDigraph &gr) : _graph(&gr) {
   1.280          node_num=_graph->nodes.size();
   1.281          arc_num=_graph->arcs.size();
   1.282        }
   1.283  
   1.284        ///Make a snapshot.
   1.285  
   1.286 -      ///Make a snapshot of the digraph.
   1.287 -      ///
   1.288 -      ///This function can be called more than once. In case of a repeated
   1.289 +      ///This function makes a snapshot of the given digraph.
   1.290 +      ///It can be called more than once. In case of a repeated
   1.291        ///call, the previous snapshot gets lost.
   1.292 -      ///\param graph The digraph we make the snapshot of.
   1.293 -      void save(SmartDigraph &graph)
   1.294 -      {
   1.295 -        _graph=&graph;
   1.296 +      void save(SmartDigraph &gr) {
   1.297 +        _graph=&gr;
   1.298          node_num=_graph->nodes.size();
   1.299          arc_num=_graph->arcs.size();
   1.300        }
   1.301  
   1.302        ///Undo the changes until a snapshot.
   1.303  
   1.304 -      ///Undo the changes until a snapshot created by save().
   1.305 -      ///
   1.306 -      ///\note After you restored a state, you cannot restore
   1.307 -      ///a later state, in other word you cannot add again the arcs deleted
   1.308 -      ///by restore().
   1.309 +      ///This function undos the changes until the last snapshot
   1.310 +      ///created by save() or Snapshot(SmartDigraph&).
   1.311        void restore()
   1.312        {
   1.313          _graph->restoreSnapshot(*this);
   1.314 @@ -420,7 +407,7 @@
   1.315  
   1.316    public:
   1.317  
   1.318 -    typedef SmartGraphBase Digraph;
   1.319 +    typedef SmartGraphBase Graph;
   1.320  
   1.321      class Node;
   1.322      class Arc;
   1.323 @@ -464,8 +451,8 @@
   1.324        explicit Arc(int id) { _id = id;}
   1.325  
   1.326      public:
   1.327 -      operator Edge() const { 
   1.328 -        return _id != -1 ? edgeFromId(_id / 2) : INVALID; 
   1.329 +      operator Edge() const {
   1.330 +        return _id != -1 ? edgeFromId(_id / 2) : INVALID;
   1.331        }
   1.332  
   1.333        Arc() {}
   1.334 @@ -480,6 +467,13 @@
   1.335      SmartGraphBase()
   1.336        : nodes(), arcs() {}
   1.337  
   1.338 +    typedef True NodeNumTag;
   1.339 +    typedef True EdgeNumTag;
   1.340 +    typedef True ArcNumTag;
   1.341 +
   1.342 +    int nodeNum() const { return nodes.size(); }
   1.343 +    int edgeNum() const { return arcs.size() / 2; }
   1.344 +    int arcNum() const { return arcs.size(); }
   1.345  
   1.346      int maxNodeId() const { return nodes.size()-1; }
   1.347      int maxEdgeId() const { return arcs.size() / 2 - 1; }
   1.348 @@ -503,7 +497,7 @@
   1.349        node._id = nodes.size() - 1;
   1.350      }
   1.351  
   1.352 -    void next(Node& node) const {
   1.353 +    static void next(Node& node) {
   1.354        --node._id;
   1.355      }
   1.356  
   1.357 @@ -511,7 +505,7 @@
   1.358        arc._id = arcs.size() - 1;
   1.359      }
   1.360  
   1.361 -    void next(Arc& arc) const {
   1.362 +    static void next(Arc& arc) {
   1.363        --arc._id;
   1.364      }
   1.365  
   1.366 @@ -519,7 +513,7 @@
   1.367        arc._id = arcs.size() / 2 - 1;
   1.368      }
   1.369  
   1.370 -    void next(Edge& arc) const {
   1.371 +    static void next(Edge& arc) {
   1.372        --arc._id;
   1.373      }
   1.374  
   1.375 @@ -616,95 +610,107 @@
   1.376    ///
   1.377    /// \brief A smart undirected graph class.
   1.378    ///
   1.379 -  /// This is a simple and fast graph implementation.
   1.380 -  /// It is also quite memory efficient, but at the price
   1.381 -  /// that <b> it does support only limited (only stack-like)
   1.382 -  /// node and arc deletions</b>.
   1.383 -  /// Except from this it conforms to
   1.384 -  /// the \ref concepts::Graph "Graph concept".
   1.385 +  /// \ref SmartGraph is a simple and fast graph implementation.
   1.386 +  /// It is also quite memory efficient but at the price
   1.387 +  /// that it does not support node and edge deletion 
   1.388 +  /// (except for the Snapshot feature).
   1.389    ///
   1.390 -  /// It also has an
   1.391 -  /// important extra feature that
   1.392 -  /// its maps are real \ref concepts::ReferenceMap "reference map"s.
   1.393 +  /// This type fully conforms to the \ref concepts::Graph "Graph concept"
   1.394 +  /// and it also provides some additional functionalities.
   1.395 +  /// Most of its member functions and nested classes are documented
   1.396 +  /// only in the concept class.
   1.397    ///
   1.398 -  /// \sa concepts::Graph.
   1.399 -  ///
   1.400 +  /// \sa concepts::Graph
   1.401 +  /// \sa SmartDigraph
   1.402    class SmartGraph : public ExtendedSmartGraphBase {
   1.403 +    typedef ExtendedSmartGraphBase Parent;
   1.404 +
   1.405    private:
   1.406 -
   1.407 -    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
   1.408 -
   1.409 -    ///SmartGraph is \e not copy constructible. Use GraphCopy() instead.
   1.410 -    ///
   1.411 +    /// Graphs are \e not copy constructible. Use GraphCopy instead.
   1.412      SmartGraph(const SmartGraph &) : ExtendedSmartGraphBase() {};
   1.413 -
   1.414 -    ///\brief Assignment of SmartGraph to another one is \e not allowed.
   1.415 -    ///Use GraphCopy() instead.
   1.416 -
   1.417 -    ///Assignment of SmartGraph to another one is \e not allowed.
   1.418 -    ///Use GraphCopy() instead.
   1.419 +    /// \brief Assignment of a graph to another one is \e not allowed.
   1.420 +    /// Use GraphCopy instead.
   1.421      void operator=(const SmartGraph &) {}
   1.422  
   1.423    public:
   1.424  
   1.425 -    typedef ExtendedSmartGraphBase Parent;
   1.426 -
   1.427      /// Constructor
   1.428  
   1.429      /// Constructor.
   1.430      ///
   1.431      SmartGraph() {}
   1.432  
   1.433 -    ///Add a new node to the graph.
   1.434 -
   1.435 -    /// \return the new node.
   1.436 +    /// \brief Add a new node to the graph.
   1.437      ///
   1.438 +    /// This function adds a new node to the graph.
   1.439 +    /// \return The new node.
   1.440      Node addNode() { return Parent::addNode(); }
   1.441  
   1.442 -    ///Add a new edge to the graph.
   1.443 -
   1.444 -    ///Add a new edge to the graph with node \c s
   1.445 -    ///and \c t.
   1.446 -    ///\return the new edge.
   1.447 -    Edge addEdge(const Node& s, const Node& t) {
   1.448 -      return Parent::addEdge(s, t);
   1.449 +    /// \brief Add a new edge to the graph.
   1.450 +    ///
   1.451 +    /// This function adds a new edge to the graph between nodes
   1.452 +    /// \c u and \c v with inherent orientation from node \c u to
   1.453 +    /// node \c v.
   1.454 +    /// \return The new edge.
   1.455 +    Edge addEdge(Node u, Node v) {
   1.456 +      return Parent::addEdge(u, v);
   1.457      }
   1.458  
   1.459      /// \brief Node validity check
   1.460      ///
   1.461 -    /// This function gives back true if the given node is valid,
   1.462 -    /// ie. it is a real node of the graph.
   1.463 +    /// This function gives back \c true if the given node is valid,
   1.464 +    /// i.e. it is a real node of the graph.
   1.465      ///
   1.466      /// \warning A removed node (using Snapshot) could become valid again
   1.467 -    /// when new nodes are added to the graph.
   1.468 +    /// if new nodes are added to the graph.
   1.469      bool valid(Node n) const { return Parent::valid(n); }
   1.470  
   1.471 +    /// \brief Edge validity check
   1.472 +    ///
   1.473 +    /// This function gives back \c true if the given edge is valid,
   1.474 +    /// i.e. it is a real edge of the graph.
   1.475 +    ///
   1.476 +    /// \warning A removed edge (using Snapshot) could become valid again
   1.477 +    /// if new edges are added to the graph.
   1.478 +    bool valid(Edge e) const { return Parent::valid(e); }
   1.479 +
   1.480      /// \brief Arc validity check
   1.481      ///
   1.482 -    /// This function gives back true if the given arc is valid,
   1.483 -    /// ie. it is a real arc of the graph.
   1.484 +    /// This function gives back \c true if the given arc is valid,
   1.485 +    /// i.e. it is a real arc of the graph.
   1.486      ///
   1.487      /// \warning A removed arc (using Snapshot) could become valid again
   1.488 -    /// when new edges are added to the graph.
   1.489 +    /// if new edges are added to the graph.
   1.490      bool valid(Arc a) const { return Parent::valid(a); }
   1.491  
   1.492 -    /// \brief Edge validity check
   1.493 -    ///
   1.494 -    /// This function gives back true if the given edge is valid,
   1.495 -    /// ie. it is a real edge of the graph.
   1.496 -    ///
   1.497 -    /// \warning A removed edge (using Snapshot) could become valid again
   1.498 -    /// when new edges are added to the graph.
   1.499 -    bool valid(Edge e) const { return Parent::valid(e); }
   1.500 -
   1.501      ///Clear the graph.
   1.502  
   1.503 -    ///Erase all the nodes and edges from the graph.
   1.504 +    ///This function erases all nodes and arcs from the graph.
   1.505      ///
   1.506      void clear() {
   1.507        Parent::clear();
   1.508      }
   1.509  
   1.510 +    /// Reserve memory for nodes.
   1.511 +
   1.512 +    /// Using this function, it is possible to avoid superfluous memory
   1.513 +    /// allocation: if you know that the graph you want to build will
   1.514 +    /// be large (e.g. it will contain millions of nodes and/or edges),
   1.515 +    /// then it is worth reserving space for this amount before starting
   1.516 +    /// to build the graph.
   1.517 +    /// \sa reserveEdge()
   1.518 +    void reserveNode(int n) { nodes.reserve(n); };
   1.519 +
   1.520 +    /// Reserve memory for edges.
   1.521 +
   1.522 +    /// Using this function, it is possible to avoid superfluous memory
   1.523 +    /// allocation: if you know that the graph you want to build will
   1.524 +    /// be large (e.g. it will contain millions of nodes and/or edges),
   1.525 +    /// then it is worth reserving space for this amount before starting
   1.526 +    /// to build the graph.
   1.527 +    /// \sa reserveNode()
   1.528 +    void reserveEdge(int m) { arcs.reserve(2 * m); };
   1.529 +
   1.530    public:
   1.531  
   1.532      class Snapshot;
   1.533 @@ -728,8 +734,8 @@
   1.534          dir.push_back(arcFromId(n));
   1.535          dir.push_back(arcFromId(n-1));
   1.536          Parent::notifier(Arc()).erase(dir);
   1.537 -        nodes[arcs[n].target].first_out=arcs[n].next_out;
   1.538 -        nodes[arcs[n-1].target].first_out=arcs[n-1].next_out;
   1.539 +        nodes[arcs[n-1].target].first_out=arcs[n].next_out;
   1.540 +        nodes[arcs[n].target].first_out=arcs[n-1].next_out;
   1.541          arcs.pop_back();
   1.542          arcs.pop_back();
   1.543        }
   1.544 @@ -743,21 +749,22 @@
   1.545  
   1.546    public:
   1.547  
   1.548 -    ///Class to make a snapshot of the digraph and to restrore to it later.
   1.549 +    ///Class to make a snapshot of the graph and to restore it later.
   1.550  
   1.551 -    ///Class to make a snapshot of the digraph and to restrore to it later.
   1.552 +    ///Class to make a snapshot of the graph and to restore it later.
   1.553      ///
   1.554 -    ///The newly added nodes and arcs can be removed using the
   1.555 -    ///restore() function.
   1.556 +    ///The newly added nodes and edges can be removed using the
   1.557 +    ///restore() function. This is the only way for deleting nodes and/or
   1.558 +    ///edges from a SmartGraph structure.
   1.559      ///
   1.560 -    ///\note After you restore a state, you cannot restore
   1.561 -    ///a later state, in other word you cannot add again the arcs deleted
   1.562 -    ///by restore() using another one Snapshot instance.
   1.563 +    ///\note After a state is restored, you cannot restore a later state, 
   1.564 +    ///i.e. you cannot add the removed nodes and edges again using
   1.565 +    ///another Snapshot instance.
   1.566      ///
   1.567 -    ///\warning If you do not use correctly the snapshot that can cause
   1.568 -    ///either broken program, invalid state of the digraph, valid but
   1.569 -    ///not the restored digraph or no change. Because the runtime performance
   1.570 -    ///the validity of the snapshot is not stored.
   1.571 +    ///\warning The validity of the snapshot is not stored due to
   1.572 +    ///performance reasons. If you do not use the snapshot correctly,
   1.573 +    ///it can cause broken program, invalid or not restored state of
   1.574 +    ///the graph or no change.
   1.575      class Snapshot
   1.576      {
   1.577        SmartGraph *_graph;
   1.578 @@ -769,36 +776,30 @@
   1.579        ///Default constructor.
   1.580  
   1.581        ///Default constructor.
   1.582 -      ///To actually make a snapshot you must call save().
   1.583 -      ///
   1.584 +      ///You have to call save() to actually make a snapshot.
   1.585        Snapshot() : _graph(0) {}
   1.586        ///Constructor that immediately makes a snapshot
   1.587  
   1.588 -      ///This constructor immediately makes a snapshot of the digraph.
   1.589 -      ///\param graph The digraph we make a snapshot of.
   1.590 -      Snapshot(SmartGraph &graph) {
   1.591 -        graph.saveSnapshot(*this);
   1.592 +      /// This constructor immediately makes a snapshot of the given graph.
   1.593 +      ///
   1.594 +      Snapshot(SmartGraph &gr) {
   1.595 +        gr.saveSnapshot(*this);
   1.596        }
   1.597  
   1.598        ///Make a snapshot.
   1.599  
   1.600 -      ///Make a snapshot of the graph.
   1.601 -      ///
   1.602 -      ///This function can be called more than once. In case of a repeated
   1.603 +      ///This function makes a snapshot of the given graph.
   1.604 +      ///It can be called more than once. In case of a repeated
   1.605        ///call, the previous snapshot gets lost.
   1.606 -      ///\param graph The digraph we make the snapshot of.
   1.607 -      void save(SmartGraph &graph)
   1.608 +      void save(SmartGraph &gr)
   1.609        {
   1.610 -        graph.saveSnapshot(*this);
   1.611 +        gr.saveSnapshot(*this);
   1.612        }
   1.613  
   1.614 -      ///Undo the changes until a snapshot.
   1.615 +      ///Undo the changes until the last snapshot.
   1.616  
   1.617 -      ///Undo the changes until a snapshot created by save().
   1.618 -      ///
   1.619 -      ///\note After you restored a state, you cannot restore
   1.620 -      ///a later state, in other word you cannot add again the arcs deleted
   1.621 -      ///by restore().
   1.622 +      ///This function undos the changes until the last snapshot
   1.623 +      ///created by save() or Snapshot(SmartGraph&).
   1.624        void restore()
   1.625        {
   1.626          _graph->restoreSnapshot(*this);