/* -*- C++ -*-

 * src/lemon/bin_heap.h - Part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2005 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_BIN_HEAP_H

#define LEMON_BIN_HEAP_H

///\ingroup auxdat

///\file

///\brief Binary Heap implementation.

///\todo It should be documented.

#include <vector>

#include <utility>

#include <functional>

namespace lemon {

  /// \addtogroup auxdat

  /// @{

   /// A Binary Heap implementation.

  ///\todo Please document...

  ///

  ///\sa FibHeap

  ///\sa Dijkstra

  template <typename Item, typename Prio, typename ItemIntMap,

	    typename Compare = std::less<Prio> >

  class BinHeap {

  public:

    typedef Item                             ItemType;

    // FIXME: stl-ben nem ezt hivjak value_type -nak, hanem a kovetkezot...

    typedef Prio                             PrioType;

    typedef std::pair<ItemType,PrioType>     PairType;

    typedef ItemIntMap                       ItemIntMapType;

    typedef Compare                          PrioCompare;

    /**

     * Each Item element have a state associated to it. It may be "in heap",

     * "pre heap" or "post heap". The later two are indifferent from the

     * heap's point of view, but may be useful to the user.

     *

     * The ItemIntMap _should_ be initialized in such way, that it maps

     * PRE_HEAP (-1) to any element to be put in the heap...

     */

    ///\todo it is used nowhere

    ///

    enum state_enum {

      IN_HEAP = 0,

      PRE_HEAP = -1,

      POST_HEAP = -2

    };

  private:

    std::vector<PairType> data;

    Compare comp;

    // FIXME: jo ez igy???

    ItemIntMap &iim;

  public:

    ///\e

    explicit BinHeap(ItemIntMap &_iim) : iim(_iim) {}

    ///\e

    explicit BinHeap(ItemIntMap &_iim, const Compare &_comp) 

      : iim(_iim), comp(_comp) {}

    ///\e

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

    ///\e

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

  private:

    static int parent(int i) { return (i-1)/2; }

    static int second_child(int i) { return 2*i+2; }

    bool less(const PairType &p1, const PairType &p2) const {

      return comp(p1.second, p2.second);

    }

    int bubble_up(int hole, PairType p);

    int bubble_down(int hole, PairType p, int length);

    void move(const PairType &p, int i) {

      data[i] = p;

      iim.set(p.first, i);

    }

    void rmidx(int h) {

      int n = data.size()-1;

      if( h>=0 && h<=n ) {

	iim.set(data[h].first, POST_HEAP);

	if ( h<n ) {

	  bubble_down(h, data[n], n);

	}

	data.pop_back();

      }

    }

  public:

    ///\e

    void push(const PairType &p) {

      int n = data.size();

      data.resize(n+1);

      bubble_up(n, p);

    }

    ///\e

    void push(const Item &i, const Prio &p) { push(PairType(i,p)); }

    ///\e

    Item top() const {

      return data[0].first;

    }

    /// Returns the prio of the top element of the heap.

    Prio prio() const {

      return data[0].second;

    }

    ///\e

    void pop() {

      rmidx(0);

    }

    ///\e

    void erase(const Item &i) {

      rmidx(iim[i]);

    }

    ///\e

    Prio operator[](const Item &i) const {

      int idx = iim[i];

      return data[idx].second;

    }

    ///\e

    void set(const Item &i, const Prio &p) {

      int idx = iim[i];

      if( idx < 0 ) {

	push(i,p);

      }

      else if( comp(p, data[idx].second) ) {

	bubble_up(idx, PairType(i,p));

      }

      else {

	bubble_down(idx, PairType(i,p), data.size());

      }

    }

    ///\e

    void decrease(const Item &i, const Prio &p) {

      int idx = iim[i];

      bubble_up(idx, PairType(i,p));

    }

    ///\e

    void increase(const Item &i, const Prio &p) {

      int idx = iim[i];

      bubble_down(idx, PairType(i,p), data.size());

    }

    ///\e

    state_enum state(const Item &i) const {

      int s = iim[i];

      if( s>=0 )

	s=0;

      return state_enum(s);

    }

  }; // class BinHeap

  template <typename K, typename V, typename M, typename C>

  int BinHeap<K,V,M,C>::bubble_up(int hole, PairType p) {

    int par = parent(hole);

    while( hole>0 && less(p,data[par]) ) {

      move(data[par],hole);

      hole = par;

      par = parent(hole);

    }

    move(p, hole);

    return hole;

  }

  template <typename K, typename V, typename M, typename C>

  int BinHeap<K,V,M,C>::bubble_down(int hole, PairType p, int length) {

    int child = second_child(hole);

    while(child < length) {

      if( less(data[child-1], data[child]) ) {

	--child;

      }

      if( !less(data[child], p) )

	goto ok;

      move(data[child], hole);

      hole = child;

      child = second_child(hole);

    }

    child--;

    if( child<length && less(data[child], p) ) {

      move(data[child], hole);

      hole=child;

    }

  ok:

    move(p, hole);

    return hole;

  }

  ///@}

} // namespace lemon

#endif // LEMON_BIN_HEAP_H