RhodeCode

/* -*- C++ -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2003-2008

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, 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.

 *

 */

///\ingroup concept

///\file

///\brief Classes for representing paths in digraphs.

///

///\todo Iterators have obsolete style

#ifndef LEMON_CONCEPT_PATH_H

#define LEMON_CONCEPT_PATH_H

#include <lemon/bits/invalid.h>

#include <lemon/bits/utility.h>

#include <lemon/concept_check.h>

namespace lemon {

  namespace concepts {

    /// \addtogroup concept

    /// @{

    /// \brief A skeleton structure for representing directed paths in

    /// a digraph.

    ///

    /// A skeleton structure for representing directed paths in a

    /// digraph.  

    /// \param _Digraph The digraph type in which the path is.

    ///

    /// In a sense, the path can be treated as a list of arcs. The

    /// lemon path type stores just this list. As a consequence it

    /// cannot enumerate the nodes in the path and the zero length

    /// paths cannot store the source.

    ///

    template <typename _Digraph>

    class Path {

    public:

      /// Type of the underlying digraph.

      typedef _Digraph Digraph;

      /// Arc type of the underlying digraph.

      typedef typename Digraph::Arc Arc;

      class ArcIt;

      /// \brief Default constructor

      Path() {}

      /// \brief Template constructor

      template <typename CPath>

      Path(const CPath& cpath) {}

      /// \brief Template assigment

      template <typename CPath>

      Path& operator=(const CPath& cpath) {}

      /// Length of the path ie. the number of arcs in the path.

      int length() const { return 0;}

      /// Returns whether the path is empty.

      bool empty() const { return true;}

      /// Resets the path to an empty path.

      void clear() {}

      /// \brief Lemon style iterator for path arcs

      ///

      /// This class is used to iterate on the arcs of the paths.

      class ArcIt {

      public:

	/// Default constructor

	ArcIt() {}

	/// Invalid constructor

	ArcIt(Invalid) {}

	/// Constructor for first arc

	ArcIt(const Path &) {}

        /// Conversion to Arc

	operator Arc() const { return INVALID; }

	/// Next arc

	ArcIt& operator++() {return *this;}

	/// Comparison operator

	bool operator==(const ArcIt&) const {return true;}

	/// Comparison operator

	bool operator!=(const ArcIt&) const {return true;}

 	/// Comparison operator

 	bool operator<(const ArcIt&) const {return false;}

      };

      template <typename _Path>

      struct Constraints {

        void constraints() {

          Path<Digraph> pc;

          _Path p, pp(pc);

          int l = p.length();

          int e = p.empty();

          p.clear();

          p = pc;

          typename _Path::ArcIt id, ii(INVALID), i(p);

          ++i;

          typename Digraph::Arc ed = i;

          e = (i == ii);

          e = (i != ii);

          e = (i < ii);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(pp);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          ignore_unused_variable_warning(ii);

          ignore_unused_variable_warning(ed);

        }

      };

    };

    namespace _path_bits {

      template <typename _Digraph, typename _Path, typename RevPathTag = void>

      struct PathDumperConstraints {

        void constraints() {

          int l = p.length();

          int e = p.empty();

          typename _Path::ArcIt id, i(p);

          ++i;

          typename _Digraph::Arc ed = i;

          e = (i == INVALID);

          e = (i != INVALID);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          ignore_unused_variable_warning(ed);

        }

        _Path& p;

      };

      template <typename _Digraph, typename _Path>

      struct PathDumperConstraints<

        _Digraph, _Path, 

        typename enable_if<typename _Path::RevPathTag, void>::type

      > {

        void constraints() {

          int l = p.length();

          int e = p.empty();

          typename _Path::RevArcIt id, i(p);

          ++i;

          typename _Digraph::Arc ed = i;

          e = (i == INVALID);

          e = (i != INVALID);

          ignore_unused_variable_warning(l);

          ignore_unused_variable_warning(e);

          ignore_unused_variable_warning(id);

          ignore_unused_variable_warning(ed);

        }

        _Path& p;

      };

    }

    /// \brief A skeleton structure for path dumpers.

    ///

    /// A skeleton structure for path dumpers. The path dumpers are

    /// the generalization of the paths. The path dumpers can

    /// enumerate the arcs of the path wheter in forward or in

    /// backward order.  In most time these classes are not used

    /// directly rather it used to assign a dumped class to a real

    /// path type.

    ///

    /// The main purpose of this concept is that the shortest path

    /// algorithms can enumerate easily the arcs in reverse order.

    /// If we would like to give back a real path from these

    /// algorithms then we should create a temporarly path object. In

    /// Lemon such algorithms gives back a path dumper what can

    /// assigned to a real path and the dumpers can be implemented as

    /// an adaptor class to the predecessor map.

    /// \param _Digraph  The digraph type in which the path is.

    ///

    /// The paths can be constructed from any path type by a

    /// template constructor or a template assignment operator.

    /// 

    template <typename _Digraph>

    class PathDumper {

    public:

      /// Type of the underlying digraph.

      typedef _Digraph Digraph;

      /// Arc type of the underlying digraph.

      typedef typename Digraph::Arc Arc;

      /// Length of the path ie. the number of arcs in the path.

      int length() const { return 0;}

      /// Returns whether the path is empty.

      bool empty() const { return true;}

      /// \brief Forward or reverse dumping

      ///

      /// If the RevPathTag is defined and true then reverse dumping

      /// is provided in the path dumper. In this case instead of the

      /// ArcIt the RevArcIt iterator should be implemented in the

      /// dumper.

      typedef False RevPathTag;

      /// \brief Lemon style iterator for path arcs

      ///

      /// This class is used to iterate on the arcs of the paths.

      class ArcIt {

      public:

	/// Default constructor

	ArcIt() {}

	/// Invalid constructor

	ArcIt(Invalid) {}

	/// Constructor for first arc

	ArcIt(const PathDumper&) {}

        /// Conversion to Arc

	operator Arc() const { return INVALID; }

	/// Next arc

	ArcIt& operator++() {return *this;}

	/// Comparison operator

	bool operator==(const ArcIt&) const {return true;}

	/// Comparison operator

	bool operator!=(const ArcIt&) const {return true;}

 	/// Comparison operator

 	bool operator<(const ArcIt&) const {return false;}

      };

      /// \brief Lemon style iterator for path arcs

      ///

      /// This class is used to iterate on the arcs of the paths in

      /// reverse direction.

      class RevArcIt {

      public:

	/// Default constructor

	RevArcIt() {}

	/// Invalid constructor

	RevArcIt(Invalid) {}

	/// Constructor for first arc

	RevArcIt(const PathDumper &) {}

        /// Conversion to Arc

	operator Arc() const { return INVALID; }

	/// Next arc

	RevArcIt& operator++() {return *this;}

	/// Comparison operator

	bool operator==(const RevArcIt&) const {return true;}

	/// Comparison operator

	bool operator!=(const RevArcIt&) const {return true;}

 	/// Comparison operator

 	bool operator<(const RevArcIt&) const {return false;}

      };

      template <typename _Path>

      struct Constraints {

        void constraints() {

          function_requires<_path_bits::

            PathDumperConstraints<Digraph, _Path> >();

        }

      };

    };

    ///@}

  }

} // namespace lemon

#endif // LEMON_CONCEPT_PATH_H

/* -*- C++ -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2003-2008

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, 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.

 *

 */

///\ingroup paths

///\file

///\brief Classes for representing paths in digraphs.

///

#ifndef LEMON_PATH_H

#define LEMON_PATH_H

#include <vector>

#include <algorithm>

#include <lemon/path_utils.h>

#include <lemon/error.h>

#include <lemon/bits/invalid.h>

namespace lemon {

  /// \addtogroup paths

  /// @{

  /// \brief A structure for representing directed paths in a digraph.

  ///

  /// A structure for representing directed path in a digraph.

  /// \param Digraph The digraph type in which the path is.

  ///

  /// In a sense, the path can be treated as a list of arcs. The

  /// lemon path type stores just this list. As a consequence it

  /// cannot enumerate the nodes in the path and the zero length paths

  /// cannot store the source.

  ///

  /// This implementation is a back and front insertable and erasable

  /// path type. It can be indexed in O(1) time. The front and back

  /// insertion and erasure is amortized O(1) time. The

  /// impelementation is based on two opposite organized vectors.

  template <typename _Digraph>

  class Path {

  public:

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

    /// \brief Default constructor

    ///

    /// Default constructor

    Path() {}

    /// \brief Template copy constructor

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    Path(const CPath& cpath) {

      copyPath(*this, cpath);

    }

    /// \brief Template copy assignment

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    Path& operator=(const CPath& cpath) {

      copyPath(*this, cpath);

      return *this;

    }

    /// \brief Lemon style iterator for path arcs

    ///

    /// This class is used to iterate on the arcs of the paths.

    class ArcIt {

      friend class Path;

    public:

      /// \brief Default constructor

      ArcIt() {}

      /// \brief Invalid constructor

      ArcIt(Invalid) : path(0), idx(-1) {}

      /// \brief Initializate the constructor to the first arc of path

      ArcIt(const Path &_path) 

        : path(&_path), idx(_path.empty() ? -1 : 0) {}

    private:

      ArcIt(const Path &_path, int _idx) 

        : path(&_path), idx(_idx) {}

    public:

      /// \brief Conversion to Arc

      operator const Arc&() const {

        return path->nth(idx);

      }

      /// \brief Next arc

      ArcIt& operator++() { 

        ++idx;

        if (idx >= path->length()) idx = -1; 

        return *this; 

      }

      /// \brief Comparison operator

      bool operator==(const ArcIt& e) const { return idx==e.idx; }

      /// \brief Comparison operator

      bool operator!=(const ArcIt& e) const { return idx!=e.idx; }

      /// \brief Comparison operator

      bool operator<(const ArcIt& e) const { return idx<e.idx; }

    private:

      const Path *path;

      int idx;

    };

    /// \brief Length of the path.

    int length() const { return head.size() + tail.size(); }

    /// \brief Returns whether the path is empty.

    bool empty() const { return head.empty() && tail.empty(); }

    /// \brief Resets the path to an empty path.

    void clear() { head.clear(); tail.clear(); }

    /// \brief Gives back the nth arc.

    ///

    /// \pre n is in the [0..length() - 1] range

    const Arc& nth(int n) const {

      return n < int(head.size()) ? *(head.rbegin() + n) :

        *(tail.begin() + (n - head.size()));

    }

    /// \brief Initializes arc iterator to point to the nth arc

    ///

    /// \pre n is in the [0..length() - 1] range

    ArcIt nthIt(int n) const {

      return ArcIt(*this, n);

    }

    /// \brief Gives back the first arc of the path

    const Arc& front() const {

      return head.empty() ? tail.front() : head.back();

    }

    /// \brief Add a new arc before the current path

    void addFront(const Arc& arc) {

      head.push_back(arc);

    }

    /// \brief Erase the first arc of the path

    void eraseFront() {

      if (!head.empty()) {

        head.pop_back();

      } else {

        head.clear();

        int halfsize = tail.size() / 2;

        head.resize(halfsize);

        std::copy(tail.begin() + 1, tail.begin() + halfsize + 1,

                  head.rbegin());

        std::copy(tail.begin() + halfsize + 1, tail.end(), tail.begin());

        tail.resize(tail.size() - halfsize - 1);

      }

    }

    /// \brief Gives back the last arc of the path

    const Arc& back() const {

      return tail.empty() ? head.front() : tail.back();

    }

    /// \brief Add a new arc behind the current path

    void addBack(const Arc& arc) {

      tail.push_back(arc);

    }

    /// \brief Erase the last arc of the path

    void eraseBack() {

      if (!tail.empty()) {

        tail.pop_back();

      } else {

        int halfsize = head.size() / 2;

        tail.resize(halfsize);

        std::copy(head.begin() + 1, head.begin() + halfsize + 1,

                  tail.rbegin());

        std::copy(head.begin() + halfsize + 1, head.end(), head.begin());

        head.resize(head.size() - halfsize - 1);

      }

    }

    typedef True BuildTag;

    template <typename CPath>

    void build(const CPath& path) {

      int len = path.length();

      tail.reserve(len);

      for (typename CPath::ArcIt it(path); it != INVALID; ++it) {

        tail.push_back(it);

      }

    }

    template <typename CPath>

    void buildRev(const CPath& path) {

      int len = path.length();

      head.reserve(len);

      for (typename CPath::RevArcIt it(path); it != INVALID; ++it) {

        head.push_back(it);

      }

    }

  protected:

    typedef std::vector<Arc> Container;

    Container head, tail;

  };

  /// \brief A structure for representing directed paths in a digraph.

  ///

  /// A structure for representing directed path in a digraph.

  /// \param Digraph The digraph type in which the path is.

  ///

  /// In a sense, the path can be treated as a list of arcs. The

  /// lemon path type stores just this list. As a consequence it

  /// cannot enumerate the nodes in the path and the zero length paths

  /// cannot store the source.

  ///

  /// This implementation is a just back insertable and erasable path

  /// type. It can be indexed in O(1) time. The back insertion and

  /// erasure is amortized O(1) time. This implementation is faster

  /// then the \c Path type because it use just one vector for the

  /// arcs.

  template <typename _Digraph>

  class SimplePath {

  public:

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

    /// \brief Default constructor

    ///

    /// Default constructor

    SimplePath() {}

    /// \brief Template copy constructor

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    SimplePath(const CPath& cpath) {

      copyPath(*this, cpath);

    }

    /// \brief Template copy assignment

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    SimplePath& operator=(const CPath& cpath) {

      copyPath(*this, cpath);

      return *this;

    }

    /// \brief Iterator class to iterate on the arcs of the paths

    ///

    /// This class is used to iterate on the arcs of the paths

    ///

    /// Of course it converts to Digraph::Arc

    class ArcIt {

      friend class SimplePath;

    public:

      /// Default constructor

      ArcIt() {}

      /// Invalid constructor

      ArcIt(Invalid) : path(0), idx(-1) {}

      /// \brief Initializate the constructor to the first arc of path

      ArcIt(const SimplePath &_path) 

        : path(&_path), idx(_path.empty() ? -1 : 0) {}

    private:

      /// Constructor with starting point

      ArcIt(const SimplePath &_path, int _idx) 

        : idx(_idx), path(&_path) {}

    public:

      ///Conversion to Digraph::Arc

      operator const Arc&() const {

        return path->nth(idx);

      }

      /// Next arc

      ArcIt& operator++() { 

        ++idx;

        if (idx >= path->length()) idx = -1; 

        return *this; 

      }

      /// Comparison operator

      bool operator==(const ArcIt& e) const { return idx==e.idx; }

      /// Comparison operator

      bool operator!=(const ArcIt& e) const { return idx!=e.idx; }

      /// Comparison operator

      bool operator<(const ArcIt& e) const { return idx<e.idx; }

    private:

      const SimplePath *path;

      int idx;

    };

    /// \brief Length of the path.

    int length() const { return data.size(); }

    /// \brief Returns whether the path is empty.

    bool empty() const { return data.empty(); }

    /// \brief Resets the path to an empty path.

    void clear() { data.clear(); }

    /// \brief Gives back the nth arc.

    ///

    /// \pre n is in the [0..length() - 1] range

    const Arc& nth(int n) const {

      return data[n];

    }

    /// \brief  Initializes arc iterator to point to the nth arc.

    ArcIt nthIt(int n) const {

      return ArcIt(*this, n);

    }

    /// \brief Gives back the first arc of the path.

    const Arc& front() const {

      return data.front();

    }

    /// \brief Gives back the last arc of the path.

    const Arc& back() const {

      return data.back();

    }

    /// \brief Add a new arc behind the current path.

    void addBack(const Arc& arc) {

      data.push_back(arc);

    }

    /// \brief Erase the last arc of the path

    void eraseBack() {

      data.pop_back();

    }

    typedef True BuildTag;

    template <typename CPath>

    void build(const CPath& path) {

      int len = path.length();

      data.resize(len);

      int index = 0;

      for (typename CPath::ArcIt it(path); it != INVALID; ++it) {

        data[index] = it;;

        ++index;

      }

    }

    template <typename CPath>

    void buildRev(const CPath& path) {

      int len = path.length();

      data.resize(len);

      int index = len;

      for (typename CPath::RevArcIt it(path); it != INVALID; ++it) {

        --index;

        data[index] = it;;

      }

    }

  protected:

    typedef std::vector<Arc> Container;

    Container data;

  };

  /// \brief A structure for representing directed paths in a digraph.

  ///

  /// A structure for representing directed path in a digraph.

  /// \param Digraph The digraph type in which the path is.

  ///

  /// In a sense, the path can be treated as a list of arcs. The

  /// lemon path type stores just this list. As a consequence it

  /// cannot enumerate the nodes in the path and the zero length paths

  /// cannot store the source.

  ///

  /// This implementation is a back and front insertable and erasable

  /// path type. It can be indexed in O(k) time, where k is the rank

  /// of the arc in the path. The length can be computed in O(n)

  /// time. The front and back insertion and erasure is O(1) time

  /// and it can be splited and spliced in O(1) time.

  template <typename _Digraph>

  class ListPath {

  public:

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

  protected:

    // the std::list<> is incompatible 

    // hard to create invalid iterator

    struct Node {

      Arc arc;

      Node *next, *prev;

    };

    Node *first, *last;

    std::allocator<Node> alloc;

  public:

    /// \brief Default constructor

    ///

    /// Default constructor

    ListPath() : first(0), last(0) {}

    /// \brief Template copy constructor

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    ListPath(const CPath& cpath) : first(0), last(0) {

      copyPath(*this, cpath);

    }

    /// \brief Destructor of the path

    ///

    /// Destructor of the path

    ~ListPath() {

      clear();

    }

    /// \brief Template copy assignment

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    ListPath& operator=(const CPath& cpath) {

      copyPath(*this, cpath);

      return *this;

    }

    /// \brief Iterator class to iterate on the arcs of the paths

    ///

    /// This class is used to iterate on the arcs of the paths

    ///

    /// Of course it converts to Digraph::Arc

    class ArcIt {

      friend class ListPath;

    public:

      /// Default constructor

      ArcIt() {}

      /// Invalid constructor

      ArcIt(Invalid) : path(0), node(0) {}

      /// \brief Initializate the constructor to the first arc of path

      ArcIt(const ListPath &_path) 

        : path(&_path), node(_path.first) {}

    protected:

      ArcIt(const ListPath &_path, Node *_node) 

        : path(&_path), node(_node) {}

    public:

      ///Conversion to Digraph::Arc

      operator const Arc&() const {

        return node->arc;

      }

      /// Next arc

      ArcIt& operator++() { 

        node = node->next;

        return *this; 

      }

      /// Comparison operator

      bool operator==(const ArcIt& e) const { return node==e.node; }

      /// Comparison operator

      bool operator!=(const ArcIt& e) const { return node!=e.node; }

      /// Comparison operator

      bool operator<(const ArcIt& e) const { return node<e.node; }

    private:

      const ListPath *path;

      Node *node;

    };

    /// \brief Gives back the nth arc.

    ///

    /// Gives back the nth arc in O(n) time.

    /// \pre n is in the [0..length() - 1] range

    const Arc& nth(int n) const {

      Node *node = first;

      for (int i = 0; i < n; ++i) {

        node = node->next;

      }

      return node->arc;

    }

    /// \brief Initializes arc iterator to point to the nth arc.

    ArcIt nthIt(int n) const {

      Node *node = first;

      for (int i = 0; i < n; ++i) {

        node = node->next;

      }

      return ArcIt(*this, node);

    }

    /// \brief Length of the path.

    int length() const {

      int len = 0;

      Node *node = first;

      while (node != 0) {

        node = node->next;

        ++len;

      }

      return len;

    }

    /// \brief Returns whether the path is empty.

    bool empty() const { return first == 0; }

    /// \brief Resets the path to an empty path.

    void clear() {

      while (first != 0) {

        last = first->next;

        alloc.destroy(first);

        alloc.deallocate(first, 1);

        first = last;

      }

    }

    /// \brief Gives back the first arc of the path

    const Arc& front() const {

      return first->arc;

    }

    /// \brief Add a new arc before the current path

    void addFront(const Arc& arc) {

      Node *node = alloc.allocate(1);

      alloc.construct(node, Node());

      node->prev = 0;

      node->next = first;

      node->arc = arc;

      if (first) {

        first->prev = node;

        first = node;

      } else {

        first = last = node;

      }

    }

    /// \brief Erase the first arc of the path

    void eraseFront() {

      Node *node = first;

      first = first->next;

      if (first) {

        first->prev = 0;

      } else {

        last = 0;

      }

      alloc.destroy(node);

      alloc.deallocate(node, 1);

    }

    /// \brief Gives back the last arc of the path.

    const Arc& back() const {

      return last->arc;

    }

    /// \brief Add a new arc behind the current path.

    void addBack(const Arc& arc) {

      Node *node = alloc.allocate(1);

      alloc.construct(node, Node());

      node->next = 0;

      node->prev = last;

      node->arc = arc;

      if (last) {

        last->next = node;

        last = node;

      } else {

        last = first = node;

      }

    }

    /// \brief Erase the last arc of the path

    void eraseBack() {

      Node *node = last;

      last = last->prev;

      if (last) {

        last->next = 0;

      } else {

        first = 0;

      }

      alloc.destroy(node);

      alloc.deallocate(node, 1);

    }

    /// \brief Splicing the given path to the current path.

    ///

    /// It splices the \c tpath to the back of the current path and \c

    /// tpath becomes empty. The time complexity of this function is

    /// O(1).

    void spliceBack(ListPath& tpath) {

      if (first) {

        if (tpath.first) {

          last->next = tpath.first;

          tpath.first->prev = last;

          last = tpath.last;

        }

      } else {

        first = tpath.first;

        last = tpath.last;

      }

      tpath.first = tpath.last = 0;

    }

    /// \brief Splicing the given path to the current path.

    ///

    /// It splices the \c tpath before the current path and \c tpath

    /// becomes empty. The time complexity of this function

    /// is O(1).

    void spliceFront(ListPath& tpath) {

      if (first) {

        if (tpath.first) {

          first->prev = tpath.last;

          tpath.last->next = first;

          first = tpath.first;

        }

      } else {

        first = tpath.first;

        last = tpath.last;

      }

      tpath.first = tpath.last = 0;

    }

    /// \brief Splicing the given path into the current path.

    ///

    /// It splices the \c tpath into the current path before the

    /// position of \c it iterator and \c tpath becomes empty. The

    /// time complexity of this function is O(1). If the \c it is \c

    /// INVALID then it will splice behind the current path.

    void splice(ArcIt it, ListPath& tpath) {

      if (it.node) {

        if (tpath.first) {

          tpath.first->prev = it.node->prev;

          if (it.node->prev) {

            it.node->prev->next = tpath.first;

          } else {

            first = tpath.first;

          }

          it.node->prev = tpath.last;

          tpath.last->next = it.node;

        }

      } else {

        if (first) {

          if (tpath.first) {

            last->next = tpath.first;

            tpath.first->prev = last;

            last = tpath.last;

          }

        } else {

          first = tpath.first;

          last = tpath.last;

        }

      }

      tpath.first = tpath.last = 0;

    }

    /// \brief Spliting the current path.

    ///

    /// It splits the current path into two parts. The part before \c

    /// it iterator will remain in the current path and the part from

    /// the it will put into the \c tpath. If the \c tpath had arcs

    /// before the operation they will be removed first.  The time

    /// complexity of this function is O(1) plus the clearing of \c

    /// tpath. If the \c it is \c INVALID then it just clears \c

    /// tpath.

    void split(ArcIt it, ListPath& tpath) {

      tpath.clear();

      if (it.node) {

        tpath.first = it.node;

        tpath.last = last;

        if (it.node->prev) {

          last = it.node->prev;

          last->next = 0;

        } else {

          first = last = 0;

        }

        it.node->prev = 0;

      }

    }

    typedef True BuildTag;

    template <typename CPath>

    void build(const CPath& path) {

      for (typename CPath::ArcIt it(path); it != INVALID; ++it) {

        addBack(it);

      }

    }

    template <typename CPath>

    void buildRev(const CPath& path) {

      for (typename CPath::RevArcIt it(path); it != INVALID; ++it) {

        addFront(it);

      }

    }

  };

  /// \brief A structure for representing directed paths in a digraph.

  ///

  /// A structure for representing directed path in a digraph.

  /// \param Digraph The digraph type in which the path is.

  ///

  /// In a sense, the path can be treated as a list of arcs. The

  /// lemon path type stores just this list. As a consequence it

  /// cannot enumerate the nodes in the path and the zero length paths

  /// cannot store the source.

  ///

  /// This implementation is completly static, so it cannot be

  /// modified exclude the assign an other path. It is intented to be

  /// used when you want to store a large number of paths because it is

  /// the most memory efficient path type in the lemon.

  template <typename _Digraph>

  class StaticPath {

  public:

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

    /// \brief Default constructor

    ///

    /// Default constructor

    StaticPath() : len(0), arcs(0) {}

    /// \brief Template copy constructor

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    StaticPath(const CPath& cpath) : arcs(0) {

      copyPath(*this, cpath);

    }

    /// \brief Destructor of the path

    ///

    /// Destructor of the path

    ~StaticPath() {

      if (arcs) delete[] arcs;

    }

    /// \brief Template copy assignment

    ///

    /// This path can be initialized with any other path type. It just

    /// makes a copy of the given path.

    template <typename CPath>

    StaticPath& operator=(const CPath& cpath) {

      copyPath(*this, cpath);

      return *this;

    }

    /// \brief Iterator class to iterate on the arcs of the paths

    ///

    /// This class is used to iterate on the arcs of the paths

    ///

    /// Of course it converts to Digraph::Arc

    class ArcIt {

      friend class StaticPath;

    public:

      /// Default constructor

      ArcIt() {}

      /// Invalid constructor

      ArcIt(Invalid) : path(0), idx(-1) {}

      /// Initializate the constructor to the first arc of path

      ArcIt(const StaticPath &_path) 

        : path(&_path), idx(_path.empty() ? -1 : 0) {}

    private:

      /// Constructor with starting point