lemon/smart_graph.h
author Peter Kovacs <kpeter@inf.elte.hu>
Sat, 20 Feb 2010 18:39:03 +0100
changeset 839 f3bc4e9b5f3a
parent 780 580af8cf2f6a
child 877 141f9c0db4a3
permissions -rw-r--r--
New heuristics for MCF algorithms (#340)
and some implementation improvements.

- A useful heuristic is added to NetworkSimplex to make the
initial pivots faster.
- A powerful global update heuristic is added to CostScaling
and the implementation is reworked with various improvements.
- Better relabeling in CostScaling to improve numerical stability
and make the code faster.
- A small improvement is made in CapacityScaling for better
delta computation.
- Add notes to the classes about the usage of vector<char> instead
of vector<bool> for efficiency reasons.
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/* -*- mode: C++; indent-tabs-mode: nil; -*-
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 *
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 * This file is a part of LEMON, a generic C++ optimization library.
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 *
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 * Copyright (C) 2003-2009
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 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_SMART_GRAPH_H
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#define LEMON_SMART_GRAPH_H
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///\ingroup graphs
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///\file
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///\brief SmartDigraph and SmartGraph classes.
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#include <vector>
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#include <lemon/core.h>
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#include <lemon/error.h>
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#include <lemon/bits/graph_extender.h>
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namespace lemon {
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  class SmartDigraph;
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  class SmartDigraphBase {
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  protected:
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    struct NodeT
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    {
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      int first_in, first_out;
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      NodeT() {}
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    };
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    struct ArcT
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    {
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      int target, source, next_in, next_out;
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      ArcT() {}
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    };
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    std::vector<NodeT> nodes;
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    std::vector<ArcT> arcs;
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  public:
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    typedef SmartDigraphBase Digraph;
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    class Node;
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    class Arc;
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  public:
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    SmartDigraphBase() : nodes(), arcs() { }
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    SmartDigraphBase(const SmartDigraphBase &_g)
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      : nodes(_g.nodes), arcs(_g.arcs) { }
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    typedef True NodeNumTag;
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    typedef True ArcNumTag;
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    int nodeNum() const { return nodes.size(); }
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    int arcNum() const { return arcs.size(); }
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    int maxNodeId() const { return nodes.size()-1; }
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    int maxArcId() const { return arcs.size()-1; }
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    Node addNode() {
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      int n = nodes.size();
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      nodes.push_back(NodeT());
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      nodes[n].first_in = -1;
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      nodes[n].first_out = -1;
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      return Node(n);
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    }
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    Arc addArc(Node u, Node v) {
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      int n = arcs.size();
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      arcs.push_back(ArcT());
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      arcs[n].source = u._id;
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      arcs[n].target = v._id;
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      arcs[n].next_out = nodes[u._id].first_out;
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      arcs[n].next_in = nodes[v._id].first_in;
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      nodes[u._id].first_out = nodes[v._id].first_in = n;
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      return Arc(n);
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    }
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    void clear() {
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      arcs.clear();
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      nodes.clear();
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    }
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    Node source(Arc a) const { return Node(arcs[a._id].source); }
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    Node target(Arc a) const { return Node(arcs[a._id].target); }
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    static int id(Node v) { return v._id; }
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    static int id(Arc a) { return a._id; }
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    static Node nodeFromId(int id) { return Node(id);}
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    static Arc arcFromId(int id) { return Arc(id);}
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    bool valid(Node n) const {
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      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
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    }
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    bool valid(Arc a) const {
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      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
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    }
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    class Node {
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      friend class SmartDigraphBase;
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      friend class SmartDigraph;
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    protected:
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      int _id;
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      explicit Node(int id) : _id(id) {}
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    public:
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      Node() {}
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      Node (Invalid) : _id(-1) {}
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      bool operator==(const Node i) const {return _id == i._id;}
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      bool operator!=(const Node i) const {return _id != i._id;}
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      bool operator<(const Node i) const {return _id < i._id;}
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    };
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    class Arc {
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      friend class SmartDigraphBase;
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      friend class SmartDigraph;
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    protected:
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      int _id;
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      explicit Arc(int id) : _id(id) {}
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    public:
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      Arc() { }
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      Arc (Invalid) : _id(-1) {}
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      bool operator==(const Arc i) const {return _id == i._id;}
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      bool operator!=(const Arc i) const {return _id != i._id;}
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      bool operator<(const Arc i) const {return _id < i._id;}
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    };
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    void first(Node& node) const {
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      node._id = nodes.size() - 1;
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    }
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    static void next(Node& node) {
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      --node._id;
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    }
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    void first(Arc& arc) const {
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      arc._id = arcs.size() - 1;
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    }
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    static void next(Arc& arc) {
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      --arc._id;
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    }
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    void firstOut(Arc& arc, const Node& node) const {
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      arc._id = nodes[node._id].first_out;
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    }
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    void nextOut(Arc& arc) const {
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      arc._id = arcs[arc._id].next_out;
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    }
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    void firstIn(Arc& arc, const Node& node) const {
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      arc._id = nodes[node._id].first_in;
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    }
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    void nextIn(Arc& arc) const {
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      arc._id = arcs[arc._id].next_in;
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    }
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  };
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  typedef DigraphExtender<SmartDigraphBase> ExtendedSmartDigraphBase;
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  ///\ingroup graphs
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  ///
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  ///\brief A smart directed graph class.
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  ///
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  ///\ref SmartDigraph is a simple and fast digraph implementation.
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  ///It is also quite memory efficient but at the price
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  ///that it does not support node and arc deletion 
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  ///(except for the Snapshot feature).
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  ///
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  ///This type fully conforms to the \ref concepts::Digraph "Digraph concept"
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  ///and it also provides some additional functionalities.
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  ///Most of its member functions and nested classes are documented
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  ///only in the concept class.
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  ///
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  ///This class provides constant time counting for nodes and arcs.
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  ///
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  ///\sa concepts::Digraph
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  ///\sa SmartGraph
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  class SmartDigraph : public ExtendedSmartDigraphBase {
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    typedef ExtendedSmartDigraphBase Parent;
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  private:
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    /// Digraphs are \e not copy constructible. Use DigraphCopy instead.
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    SmartDigraph(const SmartDigraph &) : ExtendedSmartDigraphBase() {};
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    /// \brief Assignment of a digraph to another one is \e not allowed.
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    /// Use DigraphCopy instead.
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    void operator=(const SmartDigraph &) {}
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  public:
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    /// Constructor
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    /// Constructor.
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    ///
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    SmartDigraph() {};
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    ///Add a new node to the digraph.
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    ///This function adds a new node to the digraph.
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    ///\return The new node.
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    Node addNode() { return Parent::addNode(); }
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    ///Add a new arc to the digraph.
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    ///This function adds a new arc to the digraph with source node \c s
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    ///and target node \c t.
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    ///\return The new arc.
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    Arc addArc(Node s, Node t) {
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      return Parent::addArc(s, t);
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    }
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    /// \brief Node validity check
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    ///
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    /// This function gives back \c true if the given node is valid,
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    /// i.e. it is a real node of the digraph.
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    ///
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    /// \warning A removed node (using Snapshot) could become valid again
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    /// if new nodes are added to the digraph.
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    bool valid(Node n) const { return Parent::valid(n); }
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    /// \brief Arc validity check
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    ///
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    /// This function gives back \c true if the given arc is valid,
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    /// i.e. it is a real arc of the digraph.
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    ///
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    /// \warning A removed arc (using Snapshot) could become valid again
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    /// if new arcs are added to the graph.
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    bool valid(Arc a) const { return Parent::valid(a); }
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    ///Split a node.
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    ///This function splits the given node. First, a new node is added
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    ///to the digraph, then the source of each outgoing arc of node \c n
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    ///is moved to this new node.
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    ///If the second parameter \c connect is \c true (this is the default
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    ///value), then a new arc from node \c n to the newly created node
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    ///is also added.
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    ///\return The newly created node.
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    ///
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    ///\note All iterators remain valid.
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    ///
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    ///\warning This functionality cannot be used together with the Snapshot
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    ///feature.
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    Node split(Node n, bool connect = true)
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    {
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      Node b = addNode();
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      nodes[b._id].first_out=nodes[n._id].first_out;
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      nodes[n._id].first_out=-1;
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      for(int i=nodes[b._id].first_out; i!=-1; i=arcs[i].next_out) {
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        arcs[i].source=b._id;
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      }
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      if(connect) addArc(n,b);
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      return b;
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    }
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    ///Clear the digraph.
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    ///This function erases all nodes and arcs from the digraph.
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    ///
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    void clear() {
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      Parent::clear();
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    }
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    /// Reserve memory for nodes.
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    /// Using this function, it is possible to avoid superfluous memory
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    /// allocation: if you know that the digraph you want to build will
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    /// be large (e.g. it will contain millions of nodes and/or arcs),
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    /// then it is worth reserving space for this amount before starting
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    /// to build the digraph.
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    /// \sa reserveArc()
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    void reserveNode(int n) { nodes.reserve(n); };
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    /// Reserve memory for arcs.
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    /// Using this function, it is possible to avoid superfluous memory
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    /// allocation: if you know that the digraph you want to build will
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    /// be large (e.g. it will contain millions of nodes and/or arcs),
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    /// then it is worth reserving space for this amount before starting
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    /// to build the digraph.
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    /// \sa reserveNode()
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    void reserveArc(int m) { arcs.reserve(m); };
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  public:
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    class Snapshot;
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  protected:
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    void restoreSnapshot(const Snapshot &s)
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    {
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      while(s.arc_num<arcs.size()) {
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        Arc arc = arcFromId(arcs.size()-1);
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        Parent::notifier(Arc()).erase(arc);
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        nodes[arcs.back().source].first_out=arcs.back().next_out;
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        nodes[arcs.back().target].first_in=arcs.back().next_in;
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        arcs.pop_back();
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      }
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      while(s.node_num<nodes.size()) {
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        Node node = nodeFromId(nodes.size()-1);
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        Parent::notifier(Node()).erase(node);
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        nodes.pop_back();
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      }
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    }
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  public:
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    ///Class to make a snapshot of the digraph and to restore it later.
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    ///Class to make a snapshot of the digraph and to restore it later.
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    ///
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    ///The newly added nodes and arcs can be removed using the
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    ///restore() function. This is the only way for deleting nodes and/or
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    ///arcs from a SmartDigraph structure.
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    ///
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    ///\note After a state is restored, you cannot restore a later state, 
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    ///i.e. you cannot add the removed nodes and arcs again using
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    ///another Snapshot instance.
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    ///
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    ///\warning Node splitting cannot be restored.
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    ///\warning The validity of the snapshot is not stored due to
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    ///performance reasons. If you do not use the snapshot correctly,
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    ///it can cause broken program, invalid or not restored state of
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    ///the digraph or no change.
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    class Snapshot
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    {
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      SmartDigraph *_graph;
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    protected:
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      friend class SmartDigraph;
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      unsigned int node_num;
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      unsigned int arc_num;
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    public:
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      ///Default constructor.
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      ///Default constructor.
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      ///You have to call save() to actually make a snapshot.
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      Snapshot() : _graph(0) {}
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      ///Constructor that immediately makes a snapshot
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      ///This constructor immediately makes a snapshot of the given digraph.
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      ///
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      Snapshot(SmartDigraph &gr) : _graph(&gr) {
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        node_num=_graph->nodes.size();
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        arc_num=_graph->arcs.size();
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      }
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      ///Make a snapshot.
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      ///This function makes a snapshot of the given digraph.
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      ///It can be called more than once. In case of a repeated
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      ///call, the previous snapshot gets lost.
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      void save(SmartDigraph &gr) {
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        _graph=&gr;
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        node_num=_graph->nodes.size();
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        arc_num=_graph->arcs.size();
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      }
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      ///Undo the changes until a snapshot.
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      ///This function undos the changes until the last snapshot
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      ///created by save() or Snapshot(SmartDigraph&).
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      void restore()
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      {
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        _graph->restoreSnapshot(*this);
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      }
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    };
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  };
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  class SmartGraphBase {
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  protected:
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    struct NodeT {
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      int first_out;
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    };
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    struct ArcT {
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      int target;
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      int next_out;
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    };
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    std::vector<NodeT> nodes;
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    std::vector<ArcT> arcs;
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    int first_free_arc;
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  public:
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    typedef SmartGraphBase Graph;
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    class Node;
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    class Arc;
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    class Edge;
alpar@209
   417
deba@109
   418
    class Node {
deba@109
   419
      friend class SmartGraphBase;
deba@109
   420
    protected:
deba@109
   421
deba@109
   422
      int _id;
deba@109
   423
      explicit Node(int id) { _id = id;}
deba@109
   424
deba@109
   425
    public:
deba@109
   426
      Node() {}
deba@109
   427
      Node (Invalid) { _id = -1; }
deba@109
   428
      bool operator==(const Node& node) const {return _id == node._id;}
deba@109
   429
      bool operator!=(const Node& node) const {return _id != node._id;}
deba@109
   430
      bool operator<(const Node& node) const {return _id < node._id;}
deba@109
   431
    };
deba@109
   432
deba@109
   433
    class Edge {
deba@109
   434
      friend class SmartGraphBase;
deba@109
   435
    protected:
deba@109
   436
deba@109
   437
      int _id;
deba@109
   438
      explicit Edge(int id) { _id = id;}
deba@109
   439
deba@109
   440
    public:
deba@109
   441
      Edge() {}
deba@109
   442
      Edge (Invalid) { _id = -1; }
deba@109
   443
      bool operator==(const Edge& arc) const {return _id == arc._id;}
deba@109
   444
      bool operator!=(const Edge& arc) const {return _id != arc._id;}
deba@109
   445
      bool operator<(const Edge& arc) const {return _id < arc._id;}
deba@109
   446
    };
deba@109
   447
deba@109
   448
    class Arc {
deba@109
   449
      friend class SmartGraphBase;
deba@109
   450
    protected:
deba@109
   451
deba@109
   452
      int _id;
deba@109
   453
      explicit Arc(int id) { _id = id;}
deba@109
   454
deba@109
   455
    public:
kpeter@329
   456
      operator Edge() const {
kpeter@329
   457
        return _id != -1 ? edgeFromId(_id / 2) : INVALID;
deba@238
   458
      }
deba@109
   459
deba@109
   460
      Arc() {}
deba@109
   461
      Arc (Invalid) { _id = -1; }
deba@109
   462
      bool operator==(const Arc& arc) const {return _id == arc._id;}
deba@109
   463
      bool operator!=(const Arc& arc) const {return _id != arc._id;}
deba@109
   464
      bool operator<(const Arc& arc) const {return _id < arc._id;}
deba@109
   465
    };
deba@109
   466
deba@109
   467
deba@109
   468
deba@109
   469
    SmartGraphBase()
deba@109
   470
      : nodes(), arcs() {}
deba@109
   471
kpeter@368
   472
    typedef True NodeNumTag;
kpeter@368
   473
    typedef True EdgeNumTag;
kpeter@368
   474
    typedef True ArcNumTag;
kpeter@368
   475
kpeter@368
   476
    int nodeNum() const { return nodes.size(); }
kpeter@368
   477
    int edgeNum() const { return arcs.size() / 2; }
kpeter@368
   478
    int arcNum() const { return arcs.size(); }
alpar@209
   479
alpar@209
   480
    int maxNodeId() const { return nodes.size()-1; }
deba@109
   481
    int maxEdgeId() const { return arcs.size() / 2 - 1; }
deba@109
   482
    int maxArcId() const { return arcs.size()-1; }
deba@109
   483
deba@109
   484
    Node source(Arc e) const { return Node(arcs[e._id ^ 1].target); }
deba@109
   485
    Node target(Arc e) const { return Node(arcs[e._id].target); }
deba@109
   486
deba@125
   487
    Node u(Edge e) const { return Node(arcs[2 * e._id].target); }
deba@125
   488
    Node v(Edge e) const { return Node(arcs[2 * e._id + 1].target); }
deba@109
   489
deba@109
   490
    static bool direction(Arc e) {
deba@109
   491
      return (e._id & 1) == 1;
deba@109
   492
    }
deba@109
   493
deba@109
   494
    static Arc direct(Edge e, bool d) {
deba@109
   495
      return Arc(e._id * 2 + (d ? 1 : 0));
deba@109
   496
    }
deba@109
   497
alpar@209
   498
    void first(Node& node) const {
deba@109
   499
      node._id = nodes.size() - 1;
deba@109
   500
    }
deba@109
   501
kpeter@778
   502
    static void next(Node& node) {
deba@109
   503
      --node._id;
deba@109
   504
    }
deba@109
   505
alpar@209
   506
    void first(Arc& arc) const {
deba@109
   507
      arc._id = arcs.size() - 1;
deba@109
   508
    }
deba@109
   509
kpeter@778
   510
    static void next(Arc& arc) {
deba@109
   511
      --arc._id;
deba@109
   512
    }
deba@109
   513
alpar@209
   514
    void first(Edge& arc) const {
deba@109
   515
      arc._id = arcs.size() / 2 - 1;
deba@109
   516
    }
deba@109
   517
kpeter@778
   518
    static void next(Edge& arc) {
deba@109
   519
      --arc._id;
deba@109
   520
    }
deba@109
   521
deba@109
   522
    void firstOut(Arc &arc, const Node& v) const {
deba@109
   523
      arc._id = nodes[v._id].first_out;
deba@109
   524
    }
deba@109
   525
    void nextOut(Arc &arc) const {
deba@109
   526
      arc._id = arcs[arc._id].next_out;
deba@109
   527
    }
deba@109
   528
deba@109
   529
    void firstIn(Arc &arc, const Node& v) const {
deba@109
   530
      arc._id = ((nodes[v._id].first_out) ^ 1);
deba@109
   531
      if (arc._id == -2) arc._id = -1;
deba@109
   532
    }
deba@109
   533
    void nextIn(Arc &arc) const {
deba@109
   534
      arc._id = ((arcs[arc._id ^ 1].next_out) ^ 1);
deba@109
   535
      if (arc._id == -2) arc._id = -1;
deba@109
   536
    }
deba@109
   537
deba@109
   538
    void firstInc(Edge &arc, bool& d, const Node& v) const {
deba@109
   539
      int de = nodes[v._id].first_out;
deba@109
   540
      if (de != -1) {
deba@109
   541
        arc._id = de / 2;
deba@109
   542
        d = ((de & 1) == 1);
deba@109
   543
      } else {
deba@109
   544
        arc._id = -1;
deba@109
   545
        d = true;
deba@109
   546
      }
deba@109
   547
    }
deba@109
   548
    void nextInc(Edge &arc, bool& d) const {
deba@109
   549
      int de = (arcs[(arc._id * 2) | (d ? 1 : 0)].next_out);
deba@109
   550
      if (de != -1) {
deba@109
   551
        arc._id = de / 2;
deba@109
   552
        d = ((de & 1) == 1);
deba@109
   553
      } else {
deba@109
   554
        arc._id = -1;
alpar@209
   555
        d = true;
deba@109
   556
      }
deba@109
   557
    }
alpar@209
   558
deba@109
   559
    static int id(Node v) { return v._id; }
deba@109
   560
    static int id(Arc e) { return e._id; }
deba@109
   561
    static int id(Edge e) { return e._id; }
deba@109
   562
deba@109
   563
    static Node nodeFromId(int id) { return Node(id);}
deba@109
   564
    static Arc arcFromId(int id) { return Arc(id);}
deba@109
   565
    static Edge edgeFromId(int id) { return Edge(id);}
deba@109
   566
alpar@209
   567
    bool valid(Node n) const {
alpar@209
   568
      return n._id >= 0 && n._id < static_cast<int>(nodes.size());
deba@149
   569
    }
alpar@209
   570
    bool valid(Arc a) const {
deba@149
   571
      return a._id >= 0 && a._id < static_cast<int>(arcs.size());
deba@149
   572
    }
alpar@209
   573
    bool valid(Edge e) const {
alpar@209
   574
      return e._id >= 0 && 2 * e._id < static_cast<int>(arcs.size());
deba@149
   575
    }
deba@149
   576
alpar@209
   577
    Node addNode() {
deba@109
   578
      int n = nodes.size();
deba@109
   579
      nodes.push_back(NodeT());
deba@109
   580
      nodes[n].first_out = -1;
alpar@209
   581
deba@109
   582
      return Node(n);
deba@109
   583
    }
alpar@209
   584
deba@138
   585
    Edge addEdge(Node u, Node v) {
deba@109
   586
      int n = arcs.size();
deba@109
   587
      arcs.push_back(ArcT());
deba@109
   588
      arcs.push_back(ArcT());
alpar@209
   589
deba@109
   590
      arcs[n].target = u._id;
deba@109
   591
      arcs[n | 1].target = v._id;
deba@109
   592
deba@109
   593
      arcs[n].next_out = nodes[v._id].first_out;
deba@109
   594
      nodes[v._id].first_out = n;
deba@109
   595
alpar@209
   596
      arcs[n | 1].next_out = nodes[u._id].first_out;
deba@109
   597
      nodes[u._id].first_out = (n | 1);
deba@109
   598
deba@109
   599
      return Edge(n / 2);
deba@109
   600
    }
alpar@209
   601
deba@109
   602
    void clear() {
deba@109
   603
      arcs.clear();
deba@109
   604
      nodes.clear();
deba@109
   605
    }
deba@109
   606
deba@109
   607
  };
deba@109
   608
deba@109
   609
  typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;
deba@109
   610
deba@109
   611
  /// \ingroup graphs
deba@109
   612
  ///
deba@109
   613
  /// \brief A smart undirected graph class.
deba@109
   614
  ///
kpeter@735
   615
  /// \ref SmartGraph is a simple and fast graph implementation.
kpeter@735
   616
  /// It is also quite memory efficient but at the price
kpeter@735
   617
  /// that it does not support node and edge deletion 
kpeter@735
   618
  /// (except for the Snapshot feature).
deba@109
   619
  ///
kpeter@735
   620
  /// This type fully conforms to the \ref concepts::Graph "Graph concept"
kpeter@735
   621
  /// and it also provides some additional functionalities.
kpeter@735
   622
  /// Most of its member functions and nested classes are documented
kpeter@735
   623
  /// only in the concept class.
kpeter@735
   624
  ///
kpeter@787
   625
  /// This class provides constant time counting for nodes, edges and arcs.
kpeter@787
   626
  ///
kpeter@735
   627
  /// \sa concepts::Graph
kpeter@735
   628
  /// \sa SmartDigraph
deba@109
   629
  class SmartGraph : public ExtendedSmartGraphBase {
kpeter@617
   630
    typedef ExtendedSmartGraphBase Parent;
kpeter@617
   631
deba@109
   632
  private:
kpeter@735
   633
    /// Graphs are \e not copy constructible. Use GraphCopy instead.
deba@109
   634
    SmartGraph(const SmartGraph &) : ExtendedSmartGraphBase() {};
kpeter@735
   635
    /// \brief Assignment of a graph to another one is \e not allowed.
kpeter@735
   636
    /// Use GraphCopy instead.
deba@109
   637
    void operator=(const SmartGraph &) {}
deba@109
   638
deba@109
   639
  public:
deba@109
   640
deba@109
   641
    /// Constructor
alpar@209
   642
deba@109
   643
    /// Constructor.
deba@109
   644
    ///
deba@109
   645
    SmartGraph() {}
deba@109
   646
kpeter@735
   647
    /// \brief Add a new node to the graph.
kpeter@735
   648
    ///
kpeter@735
   649
    /// This function adds a new node to the graph.
kpeter@559
   650
    /// \return The new node.
deba@109
   651
    Node addNode() { return Parent::addNode(); }
alpar@209
   652
kpeter@735
   653
    /// \brief Add a new edge to the graph.
kpeter@735
   654
    ///
kpeter@735
   655
    /// This function adds a new edge to the graph between nodes
kpeter@735
   656
    /// \c u and \c v with inherent orientation from node \c u to
kpeter@735
   657
    /// node \c v.
kpeter@735
   658
    /// \return The new edge.
kpeter@735
   659
    Edge addEdge(Node u, Node v) {
kpeter@735
   660
      return Parent::addEdge(u, v);
deba@109
   661
    }
deba@109
   662
deba@149
   663
    /// \brief Node validity check
deba@149
   664
    ///
kpeter@735
   665
    /// This function gives back \c true if the given node is valid,
kpeter@735
   666
    /// i.e. it is a real node of the graph.
deba@149
   667
    ///
deba@149
   668
    /// \warning A removed node (using Snapshot) could become valid again
kpeter@735
   669
    /// if new nodes are added to the graph.
deba@149
   670
    bool valid(Node n) const { return Parent::valid(n); }
deba@149
   671
kpeter@735
   672
    /// \brief Edge validity check
kpeter@735
   673
    ///
kpeter@735
   674
    /// This function gives back \c true if the given edge is valid,
kpeter@735
   675
    /// i.e. it is a real edge of the graph.
kpeter@735
   676
    ///
kpeter@735
   677
    /// \warning A removed edge (using Snapshot) could become valid again
kpeter@735
   678
    /// if new edges are added to the graph.
kpeter@735
   679
    bool valid(Edge e) const { return Parent::valid(e); }
kpeter@735
   680
deba@149
   681
    /// \brief Arc validity check
deba@149
   682
    ///
kpeter@735
   683
    /// This function gives back \c true if the given arc is valid,
kpeter@735
   684
    /// i.e. it is a real arc of the graph.
deba@149
   685
    ///
deba@149
   686
    /// \warning A removed arc (using Snapshot) could become valid again
kpeter@735
   687
    /// if new edges are added to the graph.
deba@149
   688
    bool valid(Arc a) const { return Parent::valid(a); }
deba@149
   689
deba@109
   690
    ///Clear the graph.
alpar@209
   691
kpeter@735
   692
    ///This function erases all nodes and arcs from the graph.
deba@109
   693
    ///
deba@109
   694
    void clear() {
deba@109
   695
      Parent::clear();
deba@109
   696
    }
deba@109
   697
kpeter@736
   698
    /// Reserve memory for nodes.
kpeter@736
   699
kpeter@736
   700
    /// Using this function, it is possible to avoid superfluous memory
kpeter@736
   701
    /// allocation: if you know that the graph you want to build will
kpeter@736
   702
    /// be large (e.g. it will contain millions of nodes and/or edges),
kpeter@736
   703
    /// then it is worth reserving space for this amount before starting
kpeter@736
   704
    /// to build the graph.
kpeter@736
   705
    /// \sa reserveEdge()
kpeter@736
   706
    void reserveNode(int n) { nodes.reserve(n); };
kpeter@736
   707
kpeter@736
   708
    /// Reserve memory for edges.
kpeter@736
   709
kpeter@736
   710
    /// Using this function, it is possible to avoid superfluous memory
kpeter@736
   711
    /// allocation: if you know that the graph you want to build will
kpeter@736
   712
    /// be large (e.g. it will contain millions of nodes and/or edges),
kpeter@736
   713
    /// then it is worth reserving space for this amount before starting
kpeter@736
   714
    /// to build the graph.
kpeter@736
   715
    /// \sa reserveNode()
kpeter@736
   716
    void reserveEdge(int m) { arcs.reserve(2 * m); };
kpeter@736
   717
deba@109
   718
  public:
alpar@209
   719
deba@109
   720
    class Snapshot;
deba@109
   721
deba@109
   722
  protected:
deba@109
   723
deba@109
   724
    void saveSnapshot(Snapshot &s)
deba@109
   725
    {
deba@109
   726
      s._graph = this;
deba@109
   727
      s.node_num = nodes.size();
deba@109
   728
      s.arc_num = arcs.size();
deba@109
   729
    }
deba@109
   730
deba@109
   731
    void restoreSnapshot(const Snapshot &s)
deba@109
   732
    {
deba@109
   733
      while(s.arc_num<arcs.size()) {
deba@109
   734
        int n=arcs.size()-1;
deba@109
   735
        Edge arc=edgeFromId(n/2);
alpar@209
   736
        Parent::notifier(Edge()).erase(arc);
deba@109
   737
        std::vector<Arc> dir;
deba@109
   738
        dir.push_back(arcFromId(n));
deba@109
   739
        dir.push_back(arcFromId(n-1));
alpar@209
   740
        Parent::notifier(Arc()).erase(dir);
kpeter@373
   741
        nodes[arcs[n-1].target].first_out=arcs[n].next_out;
kpeter@373
   742
        nodes[arcs[n].target].first_out=arcs[n-1].next_out;
alpar@209
   743
        arcs.pop_back();
alpar@209
   744
        arcs.pop_back();
deba@109
   745
      }
deba@109
   746
      while(s.node_num<nodes.size()) {
deba@109
   747
        int n=nodes.size()-1;
deba@109
   748
        Node node = nodeFromId(n);
alpar@209
   749
        Parent::notifier(Node()).erase(node);
alpar@209
   750
        nodes.pop_back();
deba@109
   751
      }
alpar@209
   752
    }
deba@109
   753
deba@109
   754
  public:
deba@109
   755
kpeter@735
   756
    ///Class to make a snapshot of the graph and to restore it later.
deba@109
   757
kpeter@735
   758
    ///Class to make a snapshot of the graph and to restore it later.
deba@109
   759
    ///
kpeter@735
   760
    ///The newly added nodes and edges can be removed using the
kpeter@735
   761
    ///restore() function. This is the only way for deleting nodes and/or
kpeter@735
   762
    ///edges from a SmartGraph structure.
deba@109
   763
    ///
kpeter@735
   764
    ///\note After a state is restored, you cannot restore a later state, 
kpeter@735
   765
    ///i.e. you cannot add the removed nodes and edges again using
kpeter@735
   766
    ///another Snapshot instance.
deba@109
   767
    ///
kpeter@735
   768
    ///\warning The validity of the snapshot is not stored due to
kpeter@735
   769
    ///performance reasons. If you do not use the snapshot correctly,
kpeter@735
   770
    ///it can cause broken program, invalid or not restored state of
kpeter@735
   771
    ///the graph or no change.
alpar@209
   772
    class Snapshot
deba@109
   773
    {
deba@109
   774
      SmartGraph *_graph;
deba@109
   775
    protected:
deba@109
   776
      friend class SmartGraph;
deba@109
   777
      unsigned int node_num;
deba@109
   778
      unsigned int arc_num;
deba@109
   779
    public:
deba@109
   780
      ///Default constructor.
alpar@209
   781
deba@109
   782
      ///Default constructor.
kpeter@735
   783
      ///You have to call save() to actually make a snapshot.
deba@109
   784
      Snapshot() : _graph(0) {}
deba@109
   785
      ///Constructor that immediately makes a snapshot
alpar@209
   786
kpeter@735
   787
      /// This constructor immediately makes a snapshot of the given graph.
kpeter@735
   788
      ///
kpeter@735
   789
      Snapshot(SmartGraph &gr) {
kpeter@735
   790
        gr.saveSnapshot(*this);
deba@109
   791
      }
deba@109
   792
deba@109
   793
      ///Make a snapshot.
deba@109
   794
kpeter@735
   795
      ///This function makes a snapshot of the given graph.
kpeter@735
   796
      ///It can be called more than once. In case of a repeated
deba@109
   797
      ///call, the previous snapshot gets lost.
kpeter@735
   798
      void save(SmartGraph &gr)
deba@109
   799
      {
kpeter@735
   800
        gr.saveSnapshot(*this);
deba@109
   801
      }
deba@109
   802
kpeter@735
   803
      ///Undo the changes until the last snapshot.
alpar@209
   804
kpeter@735
   805
      ///This function undos the changes until the last snapshot
kpeter@735
   806
      ///created by save() or Snapshot(SmartGraph&).
deba@109
   807
      void restore()
deba@109
   808
      {
deba@109
   809
        _graph->restoreSnapshot(*this);
deba@109
   810
      }
deba@109
   811
    };
deba@109
   812
  };
alpar@209
   813
deba@109
   814
} //namespace lemon
deba@109
   815
deba@109
   816
deba@109
   817
#endif //LEMON_SMART_GRAPH_H