/* -*- C++ -*-

 *

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

 *

 * Copyright (C) 2003-2006

 * 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.

 *

 */

#ifndef LEMON_FREDMAN_TARJAN_H

#define LEMON_FREDMAN_TARJAN_H

///\ingroup spantree

///\file

///\brief FredmanTarjan algorithm to compute minimum spanning forest.

#include <limits>

#include <vector>

#include <lemon/list_graph.h>

#include <lemon/smart_graph.h>

#include <lemon/fib_heap.h>

#include <lemon/radix_sort.h>

#include <lemon/bits/invalid.h>

#include <lemon/error.h>

#include <lemon/maps.h>

#include <lemon/bits/traits.h>

#include <lemon/graph_utils.h>

#include <lemon/concepts/ugraph.h>

namespace lemon {

  ///Default traits class of FredmanTarjan class.

  ///Default traits class of FredmanTarjan class.

  ///\param GR Graph type.

  ///\param CM Type of cost map.

  template<class GR, class CM>

  struct FredmanTarjanDefaultTraits{

    ///The graph type the algorithm runs on. 

    typedef GR UGraph;

    ///The type of the map that stores the edge costs.

    ///The type of the map that stores the edge costs.

    ///It must meet the \ref concepts::ReadMap "ReadMap" concept.

    typedef CM CostMap;

    //The type of the cost of the edges.

    typedef typename CM::Value Value;

    ///The type of the map that stores whether an edge is in the

    ///spanning tree or not.

    ///The type of the map that stores whether an edge is in the

    ///spanning tree or not.

    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.

    ///By default it is a BoolEdgeMap.

    typedef typename UGraph::template UEdgeMap<bool> TreeMap;

    ///Instantiates a TreeMap.

    ///This function instantiates a \ref TreeMap.

    ///\param _graph is the graph, to which

    ///we would like to define the \ref TreeMap

    static TreeMap *createTreeMap(const GR &_graph){

      return new TreeMap(_graph);

    }

  };

  ///%FredmanTarjan algorithm class to find a minimum spanning tree.

  /// \ingroup spantree 

  ///

  ///This class provides an efficient implementation of %FredmanTarjan

  ///algorithm whitch is sometimes a bit quicker than the Prim

  ///algorithm on larger graphs.  Due to the structure of the

  ///algorithm, it has less controll functions than Prim.

  ///

  /// The running time is \f$ O(e\beta(e,n)) \f$ where 

  /// \f$ \beta(e,n) = \min\{ i | \log^{i}(n) \le e/n\} \f$ and 

  /// \f$ \log^{i+1}(n)=\log(\log^{i}(n)) \f$

  ///

  ///The edge costs are passed to the algorithm using a \ref

  ///concepts::ReadMap "ReadMap", so it is easy to change it to any

  ///kind of cost.

  ///

  ///The type of the cost is determined by the \ref

  ///concepts::ReadMap::Value "Value" of the cost map.

  ///

  ///\param GR The graph type the algorithm runs on. The default value

  ///is \ref ListUGraph. The value of GR is not used directly by

  ///FredmanTarjan, it is only passed to \ref

  ///FredmanTarjanDefaultTraits.

  ///

  ///\param CM This read-only UEdgeMap determines the costs of the

  ///edges. It is read once for each edge, so the map may involve in

  ///relatively time consuming process to compute the edge cost if it

  ///is necessary. The default map type is \ref

  ///concepts::UGraph::UEdgeMap "UGraph::UEdgeMap<int>". The value of

  ///CM is not used directly by FredmanTarjan, it is only passed to

  ///\ref FredmanTarjanDefaultTraits.

  ///

  ///\param TR Traits class to set various data types used by the

  ///algorithm.  The default traits class is \ref

  ///FredmanTarjanDefaultTraits "FredmanTarjanDefaultTraits<GR,CM>".

  ///See \ref FredmanTarjanDefaultTraits for the documentation of a

  ///FredmanTarjan traits class.

  ///

  ///\author Balazs Attila Mihaly

#ifdef DOXYGEN

  template <typename GR,

	    typename CM,

	    typename TR>

#else

  template <typename GR=ListUGraph,

	    typename CM=typename GR::template UEdgeMap<int>,

	    typename TR=FredmanTarjanDefaultTraits<GR,CM> >

#endif

  class FredmanTarjan {

  public:

    ///\brief \ref Exception for uninitialized parameters.

    ///

    ///This error represents problems in the initialization

    ///of the parameters of the algorithms.

    class UninitializedParameter : public lemon::UninitializedParameter {

    public:

      virtual const char* what() const throw() {

	return "lemon::FredmanTarjan::UninitializedParameter";

      }

    };

    typedef GR Graph;

    typedef TR Traits;

    ///The type of the underlying graph.

    typedef typename TR::UGraph UGraph;

    ///\e

    typedef typename UGraph::Node Node;

    ///\e

    typedef typename UGraph::NodeIt NodeIt;

    ///\e

    typedef typename UGraph::UEdge UEdge;

    ///\e

    typedef typename UGraph::UEdgeIt UEdgeIt;

    ///\e

    typedef typename UGraph::IncEdgeIt IncEdgeIt;

    ///The type of the cost of the edges.

    typedef typename TR::CostMap::Value Value;

    ///The type of the map that stores the edge costs.

    typedef typename TR::CostMap CostMap;

    ///Edges of the spanning tree.

    typedef typename TR::TreeMap TreeMap;

  private:

    ///Pointer to the underlying graph.

    const UGraph *graph;

    ///Pointer to the cost map

    const CostMap *cost;

    ///Pointer to the map of tree edges.

    TreeMap *_tree;

    ///Indicates if \ref _tree is locally allocated (\c true) or not.

    bool local_tree;

    ///Creates the maps if necessary.

    void create_maps(){

      if(!_tree){

	local_tree=true;

	_tree=Traits::createTreeMap(*graph);

      }

    }

  public :

    typedef FredmanTarjan Create;

    ///\name Named template parameters

    ///@{

    template <class TM>

    struct DefTreeMapTraits : public Traits {

      typedef TM TreeMap;

      static TreeMap *createTreeMap(const UGraph &) {

	throw UninitializedParameter();

      }

    };

    ///\ref named-templ-param "Named parameter" for setting TreeMap 

    ///\ref named-templ-param "Named parameter" for setting TreeMap

    ///

    template <class TM>

    struct DefTreeMap

      : public FredmanTarjan< UGraph, CostMap, DefTreeMapTraits<TM> > { 

      typedef FredmanTarjan< UGraph, CostMap, DefTreeMapTraits<TM> > Create;

    };

    ///@}

  protected:

    FredmanTarjan() {}

  private:

    template<class SrcGraph,class OrigMap,class Heap,class HeapCrossRef,

             class ProcessedMap,class PredMap>

    void processNextTree(const SrcGraph& graph,const OrigMap& orig,

                         Heap &heap, HeapCrossRef& crossref,

                         ProcessedMap& processed,PredMap& pred,

                         int& tree_counter,const int limit){

      std::vector<typename SrcGraph::Node> tree_nodes;

      int tree_index=tree_counter;

      bool stop=false;

      while(!heap.empty() && !stop){

        typename SrcGraph::Node v=heap.top();

        heap.pop();

	if(processed[v]!=-1){

	  heap.state(v,Heap::PRE_HEAP);

	  tree_index=processed[v];

	  _tree->set(orig[pred[v]],true);

	  stop=true;

	  break;

        }

	tree_nodes.push_back(v);

	for(typename SrcGraph::IncEdgeIt e(graph,v);e!=INVALID;++e){

	  typename SrcGraph::Node w=graph.oppositeNode(v,e);

	  switch(heap.state(w)){

	  case Heap::PRE_HEAP:

	    if(heap.size()>=limit){

	      stop=true;

	    }

	    else{

	      heap.push(w,(*cost)[orig[e]]);

	      pred.set(w,e);

	    }

	    break;

	  case Heap::IN_HEAP:

	    if ((*cost)[orig[e]]<heap[w]){

	      heap.decrease(w,(*cost)[orig[e]]); 

	      pred.set(w,e);

	    }

	    break;

	  case Heap::POST_HEAP:

	    break;

	  }

	}

      }

      for(int i=1;i<(int)tree_nodes.size();++i){

	_tree->set(orig[pred[tree_nodes[i]]],true);

        processed.set(tree_nodes[i],tree_index);

        crossref[tree_nodes[i]] = Heap::PRE_HEAP;

      }

      processed.set(tree_nodes[0],tree_index);

      crossref[tree_nodes[0]] = Heap::PRE_HEAP;

      while (!heap.empty()) {

        typename SrcGraph::Node v=heap.top();

	heap.pop();

        crossref[v] = Heap::PRE_HEAP;

      }

      heap.clear();

      if(!stop)++tree_counter;

    }

    template<class SrcGraph,class OrigMap,class ProcessedMap>

    void createTrees(const SrcGraph& graph, const OrigMap& orig, 

                     ProcessedMap& processed,

                     int edgenum,int& tree_counter){

      typedef typename SrcGraph::Node Node;

      typedef typename SrcGraph::UEdge UEdge;

      typedef typename SrcGraph::NodeIt NodeIt;

      typedef typename SrcGraph::template NodeMap<int> HeapCrossRef;

      typedef typename SrcGraph::template NodeMap<UEdge> PredMap;

      HeapCrossRef crossref(graph,-1);

      FibHeap<Value,HeapCrossRef> heap(crossref);

      PredMap pred(graph,INVALID);

      int rate=2*edgenum/countNodes(graph);

      int limit=(rate>std::numeric_limits<int>::digits)?

      std::numeric_limits<int>::max() : (1<<rate);

      for(NodeIt i(graph);i!=INVALID;++i){

	if(processed[i]==-1){

	  heap.push(i, Value());

	  processNextTree(graph,orig,heap,crossref,

                          processed,pred,tree_counter,limit);

	}

      }

    }

    template<class SrcGraph,class DestGraph,class SrcOrigMap,

             class DestOrigMap,class ProcessedMap>

    void collect(const SrcGraph& srcgraph,const SrcOrigMap& srcorig,

                 DestGraph& destgraph,DestOrigMap& destorig,

                 const ProcessedMap& processed,const int tree_counter){

      typedef typename SrcGraph::Node Node;

      typedef typename DestGraph::Node DNode;

      typedef typename SrcGraph::UEdge UEdge;

      typedef typename DestGraph::UEdge DUEdge;

      typedef typename SrcGraph::Edge Edge;

      typedef typename SrcGraph::EdgeIt EdgeIt;

      std::vector<Edge> edges;

      std::vector<DNode> nodes(tree_counter, INVALID);

      for(EdgeIt i(srcgraph);i!=INVALID;++i){

	if(processed[srcgraph.source(i)]<processed[srcgraph.target(i)]){

	  edges.push_back(i);

          if(nodes[processed[srcgraph.source(i)]]==INVALID) {

	    nodes[processed[srcgraph.source(i)]]=destgraph.addNode();

	  }

          if(nodes[processed[srcgraph.target(i)]]==INVALID) {

	    nodes[processed[srcgraph.target(i)]]=destgraph.addNode();

	  }

	}

      }

      radixSort(edges.begin(),edges.end(),

                mapFunctor(composeMap(processed,sourceMap(srcgraph))));

      counterSort(edges.begin(),edges.end(),

                  mapFunctor(composeMap(processed,targetMap(srcgraph))));

      for(int i=0;i!=(int)edges.size();++i){

	int srcproc=processed[srcgraph.source(edges[i])];

	int trgproc=processed[srcgraph.target(edges[i])];

        Value minval=(*cost)[srcorig[edges[i]]];

        UEdge minpos=edges[i];

	while (i+1!=(int)edges.size() && 

               srcproc==processed[srcgraph.source(edges[i+1])] &&

	  trgproc==processed[srcgraph.target(edges[i+1])]) {

	  if (minval>(*cost)[srcorig[edges[i+1]]]) {

            minval=(*cost)[srcorig[edges[i+1]]];

            minpos=edges[i+1];

	  }

          ++i;

	} 

	destorig[destgraph.addEdge(nodes[srcproc],nodes[trgproc])]=

          srcorig[minpos];

      }

    }

    template<class SrcGraph,class OrigMap>

    void phase(const SrcGraph& graph,const OrigMap& orig,int edgenum){

      int tree_counter = 0;

      typename SrcGraph::template NodeMap<int> processed(graph,-1);

      SmartUGraph destgraph;

      SmartUGraph::UEdgeMap<typename OrigMap::Value> destorig(destgraph);

      createTrees(graph,orig,processed,edgenum,tree_counter);

      collect(graph,orig,destgraph,destorig,processed,tree_counter);

      if (countNodes(destgraph)>1) {

        phase(destgraph,destorig,edgenum);

      }

    }

  public:      

    ///Constructor.

    ///\param _graph the graph the algorithm will run on.

    ///\param _cost the cost map used by the algorithm.

    FredmanTarjan(const UGraph& _graph, const CostMap& _cost) :

      graph(&_graph), cost(&_cost),

      _tree(0), local_tree(false)

    {

      checkConcept<concepts::UGraph, UGraph>();

    }

    ///Destructor.

    ~FredmanTarjan(){

      if(local_tree) delete _tree;

    }

    ///Sets the cost map.

    ///Sets the cost map.

    ///\return <tt> (*this) </tt>

    FredmanTarjan &costMap(const CostMap &m){

      cost = &m;

      return *this;

    }

    ///Sets the map storing the tree edges.

    ///Sets the map storing the tree edges.

    ///If you don't use this function before calling \ref run(),

    ///it will allocate one. The destuctor deallocates this

    ///automatically allocated map, of course.

    ///By default this is a BoolEdgeMap.

    ///\return <tt> (*this) </tt>

    FredmanTarjan &treeMap(TreeMap &m){

      if(local_tree) {

	delete _tree;

	local_tree=false;

      }

      _tree = &m;

      return *this;

    }

  public:

    ///\name Execution control

    ///The simplest way to execute the algorithm is to use

    ///one of the member functions called \c run(...).

    ///@{

    ///Initializes the internal data structures.

    ///Initializes the internal data structures.

    ///

    void init(){

      create_maps();

      for(typename Graph::UEdgeIt i(*graph);i!=INVALID;++i){

	_tree->set(i,false);

      }

    }

    ///Executes the algorithm.

    ///Executes the algorithm.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///This method runs the %FredmanTarjan algorithm from the node(s)

    ///in order to compute the

    ///minimum spanning tree.

    void start(){

	phase(*graph,identityMap<UEdge>(),countEdges(*graph));

    }

    ///Runs %FredmanTarjan algorithm.

    ///This method runs the %FredmanTarjan algorithm

    ///in order to compute the minimum spanning forest.

    ///

    ///\note ft.run() is just a shortcut of the following code.

    ///\code

    ///  ft.init();

    ///  ft.start();

    ///\endcode

    void run() {

      init();

      start();

    }

    ///@}

    ///\name Query Functions

    ///The result of the %FredmanTarjan algorithm can be obtained using these

    ///functions.\n

    ///Before the use of these functions,

    ///either run() or start() must be called.

    ///@{

    ///Returns a reference to the tree edges map.

    ///Returns a reference to the TreeEdgeMap of the edges of the

    ///minimum spanning tree. The value of the map is \c true only if the 

    ///edge is in the minimum spanning tree.

    ///

    ///\pre \ref run() or \ref start() must be called before using this 

    ///function.

    const TreeMap &treeMap() const { return *_tree;}

    ///Sets the tree edges map.

    ///Sets the TreeMap of the edges of the minimum spanning tree.

    ///The map values belonging to the edges of the minimum

    ///spanning tree are set to \c tree_edge_value or \c true by default 

    ///while the edge values not belonging to the minimum spanning tree are 

    ///set to

    ///\c tree_default_value or \c false by default.

    ///

    ///\pre \ref run() or \ref start() must be called before using this 

    ///function.

    template<class TreeMap>

    void treeEdges(

        TreeMap& tree,

        const typename TreeMap::Value& tree_edge_value=true,

        const typename TreeMap::Value& tree_default_value=false) const {

      for(typename UGraph::UEdgeIt i(*graph);i!=INVALID;++i){

	(*_tree)[i]?tree.set(i,tree_edge_value):tree.set(i,tree_default_value);

      }

    }

    ///\brief Checks if an edge is in the spanning tree or not.

    ///Checks if an edge is in the spanning tree or not.

    ///\param e is the edge that will be checked

    ///\return \c true if e is in the spanning tree, \c false otherwise

    bool tree(UEdge e){

      return (*_tree)[e];

    }

    ///@}

  };

  /// \ingroup spantree

  ///

  /// \brief Function type interface for FredmanTarjan algorithm.

  ///

  /// Function type interface for FredmanTarjan algorithm.

  /// \param graph the UGraph that the algorithm runs on

  /// \param cost the CostMap of the edges

  /// \retval tree the EdgeMap that contains whether an edge is in the 

  /// spanning tree or not

  ///

  /// \sa Prim

  template<class Graph,class CostMap,class TreeMap>

  void fredmanTarjan(const Graph& graph, const CostMap& cost,TreeMap& tree){

    typename FredmanTarjan<Graph,CostMap>::template DefTreeMap<TreeMap>::

      Create ft(graph,cost);

    ft.treeMap(tree);

    ft.run();

  }

} //END OF NAMESPACE LEMON

#endif