diff -r 2d6c8075d9d0 -r 818510fa3d99 src/lemon/list_graph.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lemon/list_graph.h	Wed Sep 29 15:30:04 2004 +0000
@@ -0,0 +1,1106 @@
+/* -*- C++ -*-
+ * src/lemon/list_graph.h - Part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Combinatorial Optimization Research Group, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+#ifndef LEMON_LIST_GRAPH_H
+#define LEMON_LIST_GRAPH_H
+
+///\ingroup graphs
+///\file
+///\brief ListGraph, SymListGraph, NodeSet and EdgeSet classes.
+
+#include <vector>
+#include <climits>
+
+#include <lemon/invalid.h>
+
+#include <lemon/map_registry.h>
+#include <lemon/array_map.h>
+
+#include <lemon/sym_map.h>
+
+#include <lemon/map_defines.h>
+
+
+namespace lemon {
+
+/// \addtogroup graphs
+/// @{
+
+  ///A list graph class.
+
+  ///This is a simple and fast erasable graph implementation.
+  ///
+  ///It conforms to the
+  ///\ref skeleton::ErasableGraph "ErasableGraph" concept.
+  ///\sa skeleton::ErasableGraph.
+  class ListGraph {
+
+    //Nodes are double linked.
+    //The free nodes are only single linked using the "next" field.
+    struct NodeT 
+    {
+      int first_in,first_out;
+      int prev, next;
+    };
+    //Edges are double linked.
+    //The free edges are only single linked using the "next_in" field.
+    struct EdgeT 
+    {
+      int head, tail;
+      int prev_in, prev_out;
+      int next_in, next_out;
+    };
+
+    std::vector<NodeT> nodes;
+    //The first node
+    int first_node;
+    //The first free node
+    int first_free_node;
+    std::vector<EdgeT> edges;
+    //The first free edge
+    int first_free_edge;
+    
+  public:
+    
+    typedef ListGraph Graph;
+    
+    class Node;
+    class Edge;
+
+    
+  public:
+
+    class NodeIt;
+    class EdgeIt;
+    class OutEdgeIt;
+    class InEdgeIt;
+
+    // Create map registries.
+    CREATE_MAP_REGISTRIES;
+    // Create node and edge maps.
+    CREATE_MAPS(ArrayMap);
+
+  public:
+
+    ListGraph() 
+      : nodes(), first_node(-1),
+	first_free_node(-1), edges(), first_free_edge(-1) {}
+
+    ListGraph(const ListGraph &_g) 
+      : nodes(_g.nodes), first_node(_g.first_node),
+	first_free_node(_g.first_free_node), edges(_g.edges),
+	first_free_edge(_g.first_free_edge) {}
+    
+    ///Number of nodes.
+    int nodeNum() const { return nodes.size(); }
+    ///Number of edges.
+    int edgeNum() const { return edges.size(); }
+
+    ///Set the expected maximum number of edges.
+
+    ///With this function, it is possible to set the expected number of edges.
+    ///The use of this fasten the building of the graph and makes
+    ///it possible to avoid the superfluous memory allocation.
+    void reserveEdge(int n) { edges.reserve(n); };
+    
+    /// Maximum node ID.
+    
+    /// Maximum node ID.
+    ///\sa id(Node)
+    int maxNodeId() const { return nodes.size()-1; } 
+    /// Maximum edge ID.
+    
+    /// Maximum edge ID.
+    ///\sa id(Edge)
+    int maxEdgeId() const { return edges.size()-1; }
+
+    Node tail(Edge e) const { return edges[e.n].tail; }
+    Node head(Edge e) const { return edges[e.n].head; }
+
+    NodeIt& first(NodeIt& v) const { 
+      v=NodeIt(*this); return v; }
+    EdgeIt& first(EdgeIt& e) const { 
+      e=EdgeIt(*this); return e; }
+    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
+      e=OutEdgeIt(*this,v); return e; }
+    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
+      e=InEdgeIt(*this,v); return e; }
+
+    /// Node ID.
+    
+    /// The ID of a valid Node is a nonnegative integer not greater than
+    /// \ref maxNodeId(). The range of the ID's is not surely continuous
+    /// and the greatest node ID can be actually less then \ref maxNodeId().
+    ///
+    /// The ID of the \ref INVALID node is -1.
+    ///\return The ID of the node \c v. 
+    static int id(Node v) { return v.n; }
+    /// Edge ID.
+    
+    /// The ID of a valid Edge is a nonnegative integer not greater than
+    /// \ref maxEdgeId(). The range of the ID's is not surely continuous
+    /// and the greatest edge ID can be actually less then \ref maxEdgeId().
+    ///
+    /// The ID of the \ref INVALID edge is -1.
+    ///\return The ID of the edge \c e. 
+    static int id(Edge e) { return e.n; }
+
+    /// Adds a new node to the graph.
+
+    /// \warning It adds the new node to the front of the list.
+    /// (i.e. the lastly added node becomes the first.)
+    Node addNode() {
+      int n;
+      
+      if(first_free_node==-1)
+	{
+	  n = nodes.size();
+	  nodes.push_back(NodeT());
+	}
+      else {
+	n = first_free_node;
+	first_free_node = nodes[n].next;
+      }
+      
+      nodes[n].next = first_node;
+      if(first_node != -1) nodes[first_node].prev = n;
+      first_node = n;
+      nodes[n].prev = -1;
+      
+      nodes[n].first_in = nodes[n].first_out = -1;
+      
+      Node nn; nn.n=n;
+
+      //Update dynamic maps
+      node_maps.add(nn);
+
+      return nn;
+    }
+    
+    Edge addEdge(Node u, Node v) {
+      int n;
+      
+      if(first_free_edge==-1)
+	{
+	  n = edges.size();
+	  edges.push_back(EdgeT());
+	}
+      else {
+	n = first_free_edge;
+	first_free_edge = edges[n].next_in;
+      }
+      
+      edges[n].tail = u.n; edges[n].head = v.n;
+
+      edges[n].next_out = nodes[u.n].first_out;
+      if(nodes[u.n].first_out != -1) edges[nodes[u.n].first_out].prev_out = n;
+      edges[n].next_in = nodes[v.n].first_in;
+      if(nodes[v.n].first_in != -1) edges[nodes[v.n].first_in].prev_in = n;
+      edges[n].prev_in = edges[n].prev_out = -1;
+	
+      nodes[u.n].first_out = nodes[v.n].first_in = n;
+
+      Edge e; e.n=n;
+
+      //Update dynamic maps
+      edge_maps.add(e);
+
+      return e;
+    }
+    
+    /// Finds an edge between two nodes.
+
+    /// Finds an edge from node \c u to node \c v.
+    ///
+    /// If \c prev is \ref INVALID (this is the default value), then
+    /// It finds the first edge from \c u to \c v. Otherwise it looks for
+    /// the next edge from \c u to \c v after \c prev.
+    /// \return The found edge or INVALID if there is no such an edge.
+    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
+    {
+      int e = (prev.n==-1)? nodes[u.n].first_out : edges[prev.n].next_out;
+      while(e!=-1 && edges[e].tail!=v.n) e = edges[e].next_out;
+      prev.n=e;
+      return prev;
+    }
+    
+  private:
+    void eraseEdge(int n) {
+      
+      if(edges[n].next_in!=-1)
+	edges[edges[n].next_in].prev_in = edges[n].prev_in;
+      if(edges[n].prev_in!=-1)
+	edges[edges[n].prev_in].next_in = edges[n].next_in;
+      else nodes[edges[n].head].first_in = edges[n].next_in;
+      
+      if(edges[n].next_out!=-1)
+	edges[edges[n].next_out].prev_out = edges[n].prev_out;
+      if(edges[n].prev_out!=-1)
+	edges[edges[n].prev_out].next_out = edges[n].next_out;
+      else nodes[edges[n].tail].first_out = edges[n].next_out;
+      
+      edges[n].next_in = first_free_edge;
+      first_free_edge = n;      
+
+      //Update dynamic maps
+      Edge e; e.n=n;
+      edge_maps.erase(e);
+
+    }
+      
+  public:
+
+    void erase(Node nn) {
+      int n=nn.n;
+      
+      int m;
+      while((m=nodes[n].first_in)!=-1) eraseEdge(m);
+      while((m=nodes[n].first_out)!=-1) eraseEdge(m);
+
+      if(nodes[n].next != -1) nodes[nodes[n].next].prev = nodes[n].prev;
+      if(nodes[n].prev != -1) nodes[nodes[n].prev].next = nodes[n].next;
+      else first_node = nodes[n].next;
+      
+      nodes[n].next = first_free_node;
+      first_free_node = n;
+
+      //Update dynamic maps
+      node_maps.erase(nn);
+
+    }
+    
+    void erase(Edge e) { eraseEdge(e.n); }
+
+    void clear() {
+      edge_maps.clear();
+      edges.clear();
+      node_maps.clear();
+      nodes.clear();
+      first_node=first_free_node=first_free_edge=-1;
+    }
+
+    class Node {
+      friend class ListGraph;
+      template <typename T> friend class NodeMap;
+       
+      friend class Edge;
+      friend class OutEdgeIt;
+      friend class InEdgeIt;
+      friend class SymEdge;
+
+    protected:
+      int n;
+      friend int ListGraph::id(Node v); 
+      Node(int nn) {n=nn;}
+    public:
+      Node() {}
+      Node (Invalid) { n=-1; }
+      bool operator==(const Node i) const {return n==i.n;}
+      bool operator!=(const Node i) const {return n!=i.n;}
+      bool operator<(const Node i) const {return n<i.n;}
+      //      ///Validity check
+      //      operator bool() { return n!=-1; }
+    };
+    
+    class NodeIt : public Node {
+      const ListGraph *G;
+      friend class ListGraph;
+    public:
+      NodeIt() : Node() { }
+      NodeIt(Invalid i) : Node(i) { }
+      NodeIt(const ListGraph& _G) : Node(_G.first_node), G(&_G) { }
+      NodeIt(const ListGraph& _G,Node n) : Node(n), G(&_G) { }
+      NodeIt &operator++() {
+	n=G->nodes[n].next; 
+	return *this; 
+      }
+      //      ///Validity check
+      //      operator bool() { return Node::operator bool(); }      
+    };
+
+    class Edge {
+      friend class ListGraph;
+      template <typename T> friend class EdgeMap;
+
+      friend class SymListGraph;
+      
+      friend class Node;
+      friend class NodeIt;
+    protected:
+      int n;
+      friend int ListGraph::id(Edge e);
+
+    public:
+      /// An Edge with id \c n.
+
+      /// \bug It should be
+      /// obtained by a member function of the Graph.
+      Edge(int nn) {n=nn;}
+
+      Edge() { }
+      Edge (Invalid) { n=-1; }
+      bool operator==(const Edge i) const {return n==i.n;}
+      bool operator!=(const Edge i) const {return n!=i.n;}
+      bool operator<(const Edge i) const {return n<i.n;}
+      //      ///Validity check
+      //      operator bool() { return n!=-1; }
+   };
+    
+    class EdgeIt : public Edge {
+      const ListGraph *G;
+      friend class ListGraph;
+    public:
+      EdgeIt(const ListGraph& _G) : Edge(), G(&_G) {
+      	int m;
+	for(m=_G.first_node;
+	    m!=-1 && _G.nodes[m].first_in == -1; m = _G.nodes[m].next);
+	n = (m==-1)?-1:_G.nodes[m].first_in;
+      }
+      EdgeIt (Invalid i) : Edge(i) { }
+      EdgeIt(const ListGraph& _G, Edge e) : Edge(e), G(&_G) { }
+      EdgeIt() : Edge() { }
+      EdgeIt &operator++() {
+	if(G->edges[n].next_in!=-1) n=G->edges[n].next_in;
+	else {
+	  int nn;
+	  for(nn=G->nodes[G->edges[n].head].next;
+	      nn!=-1 && G->nodes[nn].first_in == -1;
+	      nn = G->nodes[nn].next) ;
+	  n = (nn==-1)?-1:G->nodes[nn].first_in;
+	}
+	return *this;
+      }
+      //      ///Validity check
+      //      operator bool() { return Edge::operator bool(); }      
+    };
+    
+    class OutEdgeIt : public Edge {
+      const ListGraph *G;
+      friend class ListGraph;
+    public: 
+      OutEdgeIt() : Edge() { }
+      OutEdgeIt(const ListGraph& _G, Edge e) : Edge(e), G(&_G) { }
+      OutEdgeIt (Invalid i) : Edge(i) { }
+
+      OutEdgeIt(const ListGraph& _G,const Node v)
+	: Edge(_G.nodes[v.n].first_out), G(&_G) {}
+      OutEdgeIt &operator++() { n=G->edges[n].next_out; return *this; }
+      //      ///Validity check
+      //      operator bool() { return Edge::operator bool(); }      
+    };
+    
+    class InEdgeIt : public Edge {
+      const ListGraph *G;
+      friend class ListGraph;
+    public: 
+      InEdgeIt() : Edge() { }
+      InEdgeIt(const ListGraph& _G, Edge e) : Edge(e), G(&_G) { }
+      InEdgeIt (Invalid i) : Edge(i) { }
+      InEdgeIt(const ListGraph& _G,Node v)
+	: Edge(_G.nodes[v.n].first_in), G(&_G) { }
+      InEdgeIt &operator++() { n=G->edges[n].next_in; return *this; }
+      //      ///Validity check
+      //      operator bool() { return Edge::operator bool(); }      
+    };
+  };
+
+  ///Graph for bidirectional edges.
+
+  ///The purpose of this graph structure is to handle graphs
+  ///having bidirectional edges. Here the function \c addEdge(u,v) adds a pair
+  ///of oppositely directed edges.
+  ///There is a new edge map type called
+  ///\ref lemon::SymListGraph::SymEdgeMap "SymEdgeMap"
+  ///that complements this
+  ///feature by
+  ///storing shared values for the edge pairs. The usual
+  ///\ref lemon::skeleton::StaticGraph::EdgeMap "EdgeMap"
+  ///can be used
+  ///as well.
+  ///
+  ///The oppositely directed edge can also be obtained easily
+  ///using \ref lemon::SymListGraph::opposite() "opposite()" member function.
+  ///
+  ///Here erase(Edge) deletes a pair of edges.
+  ///
+  ///\todo this date structure need some reconsiderations. Maybe it
+  ///should be implemented independently from ListGraph.
+  
+  class SymListGraph : public ListGraph
+  {
+  public:
+
+    typedef SymListGraph Graph;
+
+    // Create symmetric map registry.
+    CREATE_SYM_EDGE_MAP_REGISTRY;
+    // Create symmetric edge map.
+    CREATE_SYM_EDGE_MAP(ArrayMap);
+
+    SymListGraph() : ListGraph() { }
+    SymListGraph(const ListGraph &_g) : ListGraph(_g) { }
+    ///Adds a pair of oppositely directed edges to the graph.
+    Edge addEdge(Node u, Node v)
+    {
+      Edge e = ListGraph::addEdge(u,v);
+      Edge f = ListGraph::addEdge(v,u);
+      sym_edge_maps.add(e);
+      sym_edge_maps.add(f);
+      
+      return e;
+    }
+
+    void erase(Node n) { ListGraph::erase(n);}
+    ///The oppositely directed edge.
+
+    ///Returns the oppositely directed
+    ///pair of the edge \c e.
+    static Edge opposite(Edge e)
+    {
+      Edge f;
+      f.n = e.n - 2*(e.n%2) + 1;
+      return f;
+    }
+    
+    ///Removes a pair of oppositely directed edges to the graph.
+    void erase(Edge e) {
+      Edge f = opposite(e);
+      sym_edge_maps.erase(e);
+      sym_edge_maps.erase(f);
+      ListGraph::erase(f);
+      ListGraph::erase(e);
+    }    
+  };
+
+
+  ///A graph class containing only nodes.
+
+  ///This class implements a graph structure without edges.
+  ///The most useful application of this class is to be the node set of an
+  ///\ref EdgeSet class.
+  ///
+  ///It conforms to 
+  ///the \ref skeleton::ExtendableGraph "ExtendableGraph" concept
+  ///with the exception that you cannot
+  ///add (or delete) edges. The usual edge iterators are exists, but they are
+  ///always \ref INVALID.
+  ///\sa skeleton::ExtendableGraph
+  ///\sa EdgeSet
+  class NodeSet {
+
+    //Nodes are double linked.
+    //The free nodes are only single linked using the "next" field.
+    struct NodeT 
+    {
+      int first_in,first_out;
+      int prev, next;
+      //      NodeT() {}
+    };
+
+    std::vector<NodeT> nodes;
+    //The first node
+    int first_node;
+    //The first free node
+    int first_free_node;
+    
+  public:
+
+    typedef NodeSet Graph;
+    
+    class Node;
+    class Edge;
+
+  public:
+
+    class NodeIt;
+    class EdgeIt;
+    class OutEdgeIt;
+    class InEdgeIt;
+    
+    // Create node map registry.
+    CREATE_NODE_MAP_REGISTRY;
+    // Create node maps.
+    CREATE_NODE_MAP(ArrayMap);
+
+    /// Creating empty map structure for edges.
+    template <typename Value>
+    class EdgeMap {
+    public:
+      EdgeMap(const Graph&) {}
+      EdgeMap(const Graph&, const Value&) {}
+
+      EdgeMap(const EdgeMap&) {}
+      template <typename CMap> EdgeMap(const CMap&) {}
+
+      EdgeMap& operator=(const EdgeMap&) {}
+      template <typename CMap> EdgeMap& operator=(const CMap&) {}
+      
+      class ConstIterator {
+      public:
+	bool operator==(const ConstIterator&) {return true;}
+	bool operator!=(const ConstIterator&) {return false;}
+      };
+
+      typedef ConstIterator Iterator;
+      
+      Iterator begin() { return Iterator();}
+      Iterator end() { return Iterator();}
+
+      ConstIterator begin() const { return ConstIterator();}
+      ConstIterator end() const { return ConstIterator();}
+
+    };
+    
+  public:
+
+    ///Default constructor
+    NodeSet() 
+      : nodes(), first_node(-1), first_free_node(-1) {}
+    ///Copy constructor
+    NodeSet(const NodeSet &_g) 
+      : nodes(_g.nodes), first_node(_g.first_node),
+	first_free_node(_g.first_free_node) {}
+    
+    ///Number of nodes.
+    int nodeNum() const { return nodes.size(); }
+    ///Number of edges.
+    int edgeNum() const { return 0; }
+
+    /// Maximum node ID.
+    
+    /// Maximum node ID.
+    ///\sa id(Node)
+    int maxNodeId() const { return nodes.size()-1; }
+    /// Maximum edge ID.
+    
+    /// Maximum edge ID.
+    ///\sa id(Edge)
+    int maxEdgeId() const { return 0; }
+
+    Node tail(Edge e) const { return INVALID; }
+    Node head(Edge e) const { return INVALID; }
+
+    NodeIt& first(NodeIt& v) const { 
+      v=NodeIt(*this); return v; }
+    EdgeIt& first(EdgeIt& e) const { 
+      e=EdgeIt(*this); return e; }
+    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
+      e=OutEdgeIt(*this,v); return e; }
+    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
+      e=InEdgeIt(*this,v); return e; }
+
+    /// Node ID.
+    
+    /// The ID of a valid Node is a nonnegative integer not greater than
+    /// \ref maxNodeId(). The range of the ID's is not surely continuous
+    /// and the greatest node ID can be actually less then \ref maxNodeId().
+    ///
+    /// The ID of the \ref INVALID node is -1.
+    ///\return The ID of the node \c v. 
+    static int id(Node v) { return v.n; }
+    /// Edge ID.
+    
+    /// The ID of a valid Edge is a nonnegative integer not greater than
+    /// \ref maxEdgeId(). The range of the ID's is not surely continuous
+    /// and the greatest edge ID can be actually less then \ref maxEdgeId().
+    ///
+    /// The ID of the \ref INVALID edge is -1.
+    ///\return The ID of the edge \c e. 
+    static int id(Edge e) { return -1; }
+
+    /// Adds a new node to the graph.
+
+    /// \warning It adds the new node to the front of the list.
+    /// (i.e. the lastly added node becomes the first.)
+    Node addNode() {
+      int n;
+      
+      if(first_free_node==-1)
+	{
+	  n = nodes.size();
+	  nodes.push_back(NodeT());
+	}
+      else {
+	n = first_free_node;
+	first_free_node = nodes[n].next;
+      }
+      
+      nodes[n].next = first_node;
+      if(first_node != -1) nodes[first_node].prev = n;
+      first_node = n;
+      nodes[n].prev = -1;
+      
+      nodes[n].first_in = nodes[n].first_out = -1;
+      
+      Node nn; nn.n=n;
+
+      //Update dynamic maps
+      node_maps.add(nn);
+
+      return nn;
+    }
+    
+    void erase(Node nn) {
+      int n=nn.n;
+      
+      if(nodes[n].next != -1) nodes[nodes[n].next].prev = nodes[n].prev;
+      if(nodes[n].prev != -1) nodes[nodes[n].prev].next = nodes[n].next;
+      else first_node = nodes[n].next;
+      
+      nodes[n].next = first_free_node;
+      first_free_node = n;
+
+      //Update dynamic maps
+      node_maps.erase(nn);
+    }
+    
+        
+    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
+    {
+      return INVALID;
+    }
+    
+    void clear() {
+      node_maps.clear();
+      nodes.clear();
+      first_node = first_free_node = -1;
+    }
+
+    class Node {
+      friend class NodeSet;
+      template <typename T> friend class NodeMap;
+      
+      friend class Edge;
+      friend class OutEdgeIt;
+      friend class InEdgeIt;
+
+    protected:
+      int n;
+      friend int NodeSet::id(Node v); 
+      Node(int nn) {n=nn;}
+    public:
+      Node() {}
+      Node (Invalid i) { n=-1; }
+      bool operator==(const Node i) const {return n==i.n;}
+      bool operator!=(const Node i) const {return n!=i.n;}
+      bool operator<(const Node i) const {return n<i.n;}
+    };
+    
+    class NodeIt : public Node {
+      const NodeSet *G;
+      friend class NodeSet;
+    public:
+      NodeIt() : Node() { }
+      NodeIt(const NodeSet& _G,Node n) : Node(n), G(&_G) { }
+      NodeIt(Invalid i) : Node(i) { }
+      NodeIt(const NodeSet& _G) : Node(_G.first_node), G(&_G) { }
+      NodeIt &operator++() {
+	n=G->nodes[n].next; 
+	return *this; 
+      }
+    };
+
+    class Edge {
+    public:
+      Edge() { }
+      Edge (Invalid) { }
+      bool operator==(const Edge i) const {return true;}
+      bool operator!=(const Edge i) const {return false;}
+      bool operator<(const Edge i) const {return false;}
+    };
+    
+    class EdgeIt : public Edge {
+    public:
+      EdgeIt(const NodeSet& G) : Edge() { }
+      EdgeIt(const NodeSet&, Edge) : Edge() { }
+      EdgeIt (Invalid i) : Edge(i) { }
+      EdgeIt() : Edge() { }
+      EdgeIt operator++() { return INVALID; }
+    };
+    
+    class OutEdgeIt : public Edge {
+      friend class NodeSet;
+    public: 
+      OutEdgeIt() : Edge() { }
+      OutEdgeIt(const NodeSet&, Edge) : Edge() { }
+      OutEdgeIt (Invalid i) : Edge(i) { }
+      OutEdgeIt(const NodeSet& G,const Node v)	: Edge() {}
+      OutEdgeIt operator++() { return INVALID; }
+    };
+    
+    class InEdgeIt : public Edge {
+      friend class NodeSet;
+    public: 
+      InEdgeIt() : Edge() { }
+      InEdgeIt(const NodeSet&, Edge) : Edge() { }
+      InEdgeIt (Invalid i) : Edge(i) { }
+      InEdgeIt(const NodeSet& G,Node v) :Edge() {}
+      InEdgeIt operator++() { return INVALID; }
+    };
+
+  };
+
+
+
+  ///Graph structure using a node set of another graph.
+
+  ///This structure can be used to establish another graph over a node set
+  /// of an existing one. The node iterator will go through the nodes of the
+  /// original graph, and the NodeMap's of both graphs will convert to
+  /// each other.
+  ///
+  ///\warning Adding or deleting nodes from the graph is not safe if an
+  ///\ref EdgeSet is currently attached to it!
+  ///
+  ///\todo Make it possible to add/delete edges from the base graph
+  ///(and from \ref EdgeSet, as well)
+  ///
+  ///\param GG The type of the graph which shares its node set with this class.
+  ///Its interface must conform to the
+  ///\ref skeleton::StaticGraph "StaticGraph" concept.
+  ///
+  ///It conforms to the 
+  ///\ref skeleton::ExtendableGraph "ExtendableGraph" concept.
+  ///\sa skeleton::ExtendableGraph.
+  ///\sa NodeSet.
+  template<typename GG>
+  class EdgeSet {
+
+    typedef GG NodeGraphType;
+
+    NodeGraphType &G;
+
+  public:
+
+    class Node;
+    class Edge;
+    class OutEdgeIt;
+    class InEdgeIt;
+    class SymEdge;
+
+    typedef EdgeSet Graph;
+
+    int id(Node v) const; 
+
+    class Node : public NodeGraphType::Node {
+      friend class EdgeSet;
+      
+      friend class Edge;
+      friend class OutEdgeIt;
+      friend class InEdgeIt;
+      friend class SymEdge;
+
+    public:
+      friend int EdgeSet::id(Node v) const; 
+    public:
+      Node() : NodeGraphType::Node() {}
+      Node (Invalid i) : NodeGraphType::Node(i) {}
+      Node(const typename NodeGraphType::Node &n) : NodeGraphType::Node(n) {}
+    };
+    
+    class NodeIt : public NodeGraphType::NodeIt {
+      friend class EdgeSet;
+    public:
+      NodeIt() : NodeGraphType::NodeIt() { }
+      NodeIt(const EdgeSet& _G,Node n) : NodeGraphType::NodeIt(_G.G,n) { }
+      NodeIt (Invalid i) : NodeGraphType::NodeIt(i) {}
+      NodeIt(const EdgeSet& _G) : NodeGraphType::NodeIt(_G.G) { }
+      NodeIt(const typename NodeGraphType::NodeIt &n)
+	: NodeGraphType::NodeIt(n) {}
+
+      operator Node() { return Node(*this);}
+      NodeIt &operator++()
+      { this->NodeGraphType::NodeIt::operator++(); return *this;} 
+    };
+
+  private:
+    //Edges are double linked.
+    //The free edges are only single linked using the "next_in" field.
+    struct NodeT 
+    {
+      int first_in,first_out;
+      NodeT() : first_in(-1), first_out(-1) { }
+    };
+
+    struct EdgeT 
+    {
+      Node head, tail;
+      int prev_in, prev_out;
+      int next_in, next_out;
+    };
+
+    
+    typename NodeGraphType::template NodeMap<NodeT> nodes;
+    
+    std::vector<EdgeT> edges;
+    //The first free edge
+    int first_free_edge;
+    
+  public:
+    
+    class Node;
+    class Edge;
+
+    class NodeIt;
+    class EdgeIt;
+    class OutEdgeIt;
+    class InEdgeIt;
+
+
+    // Create edge map registry.
+    CREATE_EDGE_MAP_REGISTRY;
+    // Create edge maps.
+    CREATE_EDGE_MAP(ArrayMap);
+
+    // Import node maps from the NodeGraphType.
+    IMPORT_NODE_MAP(NodeGraphType, graph.G, EdgeSet, graph);
+    
+    
+  public:
+
+    ///Constructor
+    
+    ///Construates a new graph based on the nodeset of an existing one.
+    ///\param _G the base graph.
+    explicit EdgeSet(NodeGraphType &_G) 
+      : G(_G), nodes(_G), edges(),
+	first_free_edge(-1) {}
+    ///Copy constructor
+
+    ///Makes a copy of an EdgeSet.
+    ///It will be based on the same graph.
+    explicit EdgeSet(const EdgeSet &_g) 
+      : G(_g.G), nodes(_g.G), edges(_g.edges),
+	first_free_edge(_g.first_free_edge) {}
+    
+    ///Number of nodes.
+    int nodeNum() const { return G.nodeNum(); }
+    ///Number of edges.
+    int edgeNum() const { return edges.size(); }
+
+    /// Maximum node ID.
+    
+    /// Maximum node ID.
+    ///\sa id(Node)
+    int maxNodeId() const { return G.maxNodeId(); }
+    /// Maximum edge ID.
+    
+    /// Maximum edge ID.
+    ///\sa id(Edge)
+    int maxEdgeId() const { return edges.size()-1; }
+
+    Node tail(Edge e) const { return edges[e.n].tail; }
+    Node head(Edge e) const { return edges[e.n].head; }
+
+    NodeIt& first(NodeIt& v) const { 
+      v=NodeIt(*this); return v; }
+    EdgeIt& first(EdgeIt& e) const { 
+      e=EdgeIt(*this); return e; }
+    OutEdgeIt& first(OutEdgeIt& e, const Node v) const { 
+      e=OutEdgeIt(*this,v); return e; }
+    InEdgeIt& first(InEdgeIt& e, const Node v) const { 
+      e=InEdgeIt(*this,v); return e; }
+
+    /// Node ID.
+    
+    /// The ID of a valid Node is a nonnegative integer not greater than
+    /// \ref maxNodeId(). The range of the ID's is not surely continuous
+    /// and the greatest node ID can be actually less then \ref maxNodeId().
+    ///
+    /// The ID of the \ref INVALID node is -1.
+    ///\return The ID of the node \c v. 
+    int id(Node v) { return G.id(v); }
+    /// Edge ID.
+    
+    /// The ID of a valid Edge is a nonnegative integer not greater than
+    /// \ref maxEdgeId(). The range of the ID's is not surely continuous
+    /// and the greatest edge ID can be actually less then \ref maxEdgeId().
+    ///
+    /// The ID of the \ref INVALID edge is -1.
+    ///\return The ID of the edge \c e. 
+    static int id(Edge e) { return e.n; }
+
+    /// Adds a new node to the graph.
+    Node addNode() { return G.addNode(); }
+    
+    Edge addEdge(Node u, Node v) {
+      int n;
+      
+      if(first_free_edge==-1)
+	{
+	  n = edges.size();
+	  edges.push_back(EdgeT());
+	}
+      else {
+	n = first_free_edge;
+	first_free_edge = edges[n].next_in;
+      }
+      
+      edges[n].tail = u; edges[n].head = v;
+
+      edges[n].next_out = nodes[u].first_out;
+      if(nodes[u].first_out != -1) edges[nodes[u].first_out].prev_out = n;
+      edges[n].next_in = nodes[v].first_in;
+      if(nodes[v].first_in != -1) edges[nodes[v].first_in].prev_in = n;
+      edges[n].prev_in = edges[n].prev_out = -1;
+	
+      nodes[u].first_out = nodes[v].first_in = n;
+
+      Edge e; e.n=n;
+
+      //Update dynamic maps
+      edge_maps.add(e);
+
+      return e;
+    }
+
+    /// Finds an edge between two nodes.
+
+    /// Finds an edge from node \c u to node \c v.
+    ///
+    /// If \c prev is \ref INVALID (this is the default value), then
+    /// It finds the first edge from \c u to \c v. Otherwise it looks for
+    /// the next edge from \c u to \c v after \c prev.
+    /// \return The found edge or INVALID if there is no such an edge.
+    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
+    {
+      int e = (prev.n==-1)? nodes[u].first_out : edges[prev.n].next_out;
+      while(e!=-1 && edges[e].tail!=v) e = edges[e].next_out;
+      prev.n=e;
+      return prev;
+    }
+    
+  private:
+    void eraseEdge(int n) {
+      
+      if(edges[n].next_in!=-1)
+	edges[edges[n].next_in].prev_in = edges[n].prev_in;
+      if(edges[n].prev_in!=-1)
+	edges[edges[n].prev_in].next_in = edges[n].next_in;
+      else nodes[edges[n].head].first_in = edges[n].next_in;
+      
+      if(edges[n].next_out!=-1)
+	edges[edges[n].next_out].prev_out = edges[n].prev_out;
+      if(edges[n].prev_out!=-1)
+	edges[edges[n].prev_out].next_out = edges[n].next_out;
+      else nodes[edges[n].tail].first_out = edges[n].next_out;
+      
+      edges[n].next_in = first_free_edge;
+      first_free_edge = -1;      
+
+      //Update dynamic maps
+      Edge e; e.n = n;
+      edge_maps.erase(e);
+    }
+      
+  public:
+
+    void erase(Edge e) { eraseEdge(e.n); }
+
+    ///Clear all edges. (Doesn't clear the nodes!)
+    void clear() {
+      edge_maps.clear();
+      edges.clear();
+      first_free_edge=-1;
+    }
+
+
+    class Edge {
+    public:
+      friend class EdgeSet;
+      template <typename T> friend class EdgeMap;
+
+      friend class Node;
+      friend class NodeIt;
+    protected:
+      int n;
+      friend int EdgeSet::id(Edge e) const;
+
+      Edge(int nn) {n=nn;}
+    public:
+      Edge() { }
+      Edge (Invalid) { n=-1; }
+      bool operator==(const Edge i) const {return n==i.n;}
+      bool operator!=(const Edge i) const {return n!=i.n;}
+      bool operator<(const Edge i) const {return n<i.n;}
+    };
+    
+    class EdgeIt : public Edge {
+      friend class EdgeSet;
+      template <typename T> friend class EdgeMap;
+    
+      const EdgeSet *G;
+    public:
+      EdgeIt(const EdgeSet& _G) : Edge(), G(&_G) {
+        NodeIt m;
+	for(G->first(m);
+	    m!=INVALID && G->nodes[m].first_in == -1;  ++m);
+	///\bug AJJAJ! This is a non sense!!!!!!!
+	this->n = m!=INVALID?-1:G->nodes[m].first_in;
+      }
+      EdgeIt(const EdgeSet& _G, Edge e) : Edge(e), G(&_G) { }
+      EdgeIt (Invalid i) : Edge(i) { }
+      EdgeIt() : Edge() { }
+      ///.
+      
+      ///\bug UNIMPLEMENTED!!!!!
+      //
+      EdgeIt &operator++() {
+	return *this;
+      }
+    };
+    
+    class OutEdgeIt : public Edge {
+      const EdgeSet *G;
+      friend class EdgeSet;
+    public: 
+      OutEdgeIt() : Edge() { }
+      OutEdgeIt (Invalid i) : Edge(i) { }
+      OutEdgeIt(const EdgeSet& _G, Edge e) : Edge(e), G(&_G) { }
+
+      OutEdgeIt(const EdgeSet& _G,const Node v) :
+	Edge(_G.nodes[v].first_out), G(&_G) { }
+      OutEdgeIt &operator++() { 
+	Edge::n = G->edges[Edge::n].next_out;
+	return *this; 
+      }
+    };
+    
+    class InEdgeIt : public Edge {
+      const EdgeSet *G;
+      friend class EdgeSet;
+    public: 
+      InEdgeIt() : Edge() { }
+      InEdgeIt (Invalid i) : Edge(i) { }
+      InEdgeIt(const EdgeSet& _G, Edge e) : Edge(e), G(&_G) { }
+      InEdgeIt(const EdgeSet& _G,Node v)
+	: Edge(_G.nodes[v].first_in), G(&_G) { }
+      InEdgeIt &operator++() { 
+	Edge::n = G->edges[Edge::n].next_in; 
+	return *this; 
+      }
+    };
+    
+  };
+
+  template<typename GG>
+  inline int EdgeSet<GG>::id(Node v) const { return G.id(v); }
+
+/// @}  
+
+} //namespace lemon
+
+#endif //LEMON_LIST_GRAPH_H