// -*- C++ -*-

/*

 *template <typename Item, 

 *          typename Prio, 

 *          typename ItemIntMap, 

 *          typename Compare = std::less<Prio> >

 * 

 *constructors:

 *

 *FibHeap(ItemIntMap),   FibHeap(ItemIntMap, Compare)

 *

 *Member functions:

 *

 *int size() : returns the number of elements in the heap

 *

 *bool empty() : true iff size()=0

 *

 *void push(Item, Prio) : pushes Item to the heap with priority Prio. If

 *     Item was already in the heap, it calls decrease(Item, Prio) 

 *

 *Item top() : returns the Item with least Prio

 *

 *Prio prio() : returns the least Prio

 *  

 *Prio get(Item) : returns Prio of Item

 *

 *void pop() : deletes the Item with least Prio

 *

 *void erase(Item) : deletes Item from the heap if it was already there

 *

 *void decrease(Item, P) : If Item was not in the heap, then it calls 

 *     push(Item, P). If item is in the heap with Prio more than P

 *     then sets its Prio to P.

 *

 *void increase(Item, P) : If Item was not in the heap, then it calls 

 *     push(Item, P). If item is in the heap with Prio less than P

 *     then sets its Prio to P.

 *

 *

 *In Fibonacci heaps, increase and erase are not efficient, in case of

 *many calls to these operations, it is better to use bin_heap.

 */

#ifndef FIB_HEAP_H

#define FIB_HEAP_H

#include <vector>

#include <functional>

#include <math.h>

namespace hugo {

  template <typename Item, typename Prio, typename ItemIntMap, 

    typename Compare = std::less<Prio> >

  class FibHeap {

    typedef Prio PrioType;

    class store;

    std::vector<store> container;

    int minimum;

    bool blank;

    ItemIntMap &iimap;

    Compare comp;

  public :

    FibHeap(ItemIntMap &_iimap) : minimum(), blank(true), iimap(_iimap) {} 

    FibHeap(ItemIntMap &_iimap, const Compare &_comp) : minimum(), 

      blank(true), iimap(_iimap), comp(_comp) {}

    int size() const {

      int s=0;

      for ( unsigned int i=0; i!=container.size(); ++i )

	if ( container[i].in ) ++s;

      return s; 

    }

   bool empty() const { return blank; }

   void push (Item const it, PrioType const value) 

   {

     int i=iimap.get(it);

     if ( i >= 0 && container[i].in ) decrease(it, value); 

     else {

       if ( i < 0 ) {

	 int s=container.size();

	 iimap.set( it, s );	

	 store st;

	 st.name=it;

	 container.push_back(st);

	 i=s;

       }

       if ( !blank ) {

	 container[container[minimum].right_neighbor].left_neighbor=i;

	 container[i].right_neighbor=container[minimum].right_neighbor;

	 container[minimum].right_neighbor=i;

	 container[i].left_neighbor=minimum;

	 if ( !comp( container[minimum].prio, value) ) minimum=i; 

       } else {

	 container[i].right_neighbor=container[i].left_neighbor=i;

	 minimum=i;	

	 blank=false;

       }

       container[i].prio=value;

     }

   }

    Item top() const {

      if ( !blank ) { 

	return container[minimum].name;

      } else {

	return Item();

      }

    }

    PrioType prio() const {

      if ( !blank ) { 

	return container[minimum].prio;

      } else {

	return PrioType();

      }

    }

    const PrioType get(const Item& it) const

    {

      int i=iimap.get(it);

      if ( i >= 0 && container[i].in ) { 

	return container[i].prio;

      } else {

	return PrioType();

      }

    }

    void pop() {

      if ( !blank ) {

	/*The first case is that there are only one root.*/

	if ( container[minimum].left_neighbor==minimum ) {

	  container[minimum].in=false;

	  if ( container[minimum].degree==0 ) blank=true; 

	  else { 

	    makeroot(container[minimum].child);

	    minimum=container[minimum].child;

	    balance();

	  } 

       } else {

	 int right=container[minimum].right_neighbor;

	 unlace(minimum);

	 container[minimum].in=false;

	 if ( container[minimum].degree > 0 ) {

	   int left=container[minimum].left_neighbor;

	   int child=container[minimum].child;

	   int last_child=container[child].left_neighbor;

	   container[left].right_neighbor=child;

	   container[child].left_neighbor=left;

	   container[right].left_neighbor=last_child;

	   container[last_child].right_neighbor=right;

	   makeroot(child);

	 }

	 minimum=right;

	 balance();

       } // the case where there are more roots

     } 

   }

   void erase (const Item& it) {

     int i=iimap.get(it);

     if ( i >= 0 && container[i].in ) { 

       if ( container[i].parent!=-1 ) {

	 int p=container[i].parent;

	 cut(i,p);	    

	 cascade(p);

	 minimum=i;     //As if its prio would be -infinity

       }

       pop();

     }

   }

   void decrease (Item it, PrioType const value) {

     int i=iimap.get(it);

     if ( i >= 0 && container[i].in ) { 

       if ( comp(value, container[i].prio) ) {

	 container[i].prio=value;

	 if ( container[i].parent!=-1 ) {

	   int p=container[i].parent;

	   if ( !comp(container[p].prio, value) ) { 

	     cut(i,p);	    

	     cascade(p);

	     if ( comp(value, container[minimum].prio) ) minimum=i; 

	   }

	 } 

       }

     } else push(it, value);

   }

    void increase (Item it, PrioType const value) {

      int i=iimap.get(it);

      if ( i >= 0 && container[i].in ) { 

	if ( comp(container[i].prio, value) ) { 

	  erase(it);

	  push(it, value);

	}

      } else push(it, value);

    }

  private:

    void balance() {      

    int maxdeg=int( floor( 2.08*log(double(container.size()))))+1;

    std::vector<int> A(maxdeg,-1); 

    /*

     *Recall that now minimum does not point to the minimum prio element.

     *We set minimum to this during balance().

     */

    int anchor=container[minimum].left_neighbor; 

    int next=minimum; 

    bool end=false; 

       do {

	int active=next;

	int d=container[active].degree;

	if ( anchor==active ) end=true;

	next = container[active].right_neighbor;

	if ( !comp(container[minimum].prio, container[active].prio) )

	  minimum=active;

	while (A[d]!=-1) {

	  if( comp(container[active].prio, container[A[d]].prio) ) {

	    fuse(active,A[d]); 

	  } else { 

	    fuse(A[d],active);

	    active=A[d];

	  } 

	  A[d]=-1;

	  ++d;

	}

	A[d]=active;

       } while ( !end );

  }

    /*

     *All the siblings of a are made roots.

     */

    void makeroot (int c)  

    {

      int s=c;

      do {  

	container[s].parent=-1;

	s=container[s].right_neighbor;

      } while ( s != c );

    }

    void cut (int a, int b) 

    {    

      /*

       *Replacing a from the children of b.

       */

      --container[b].degree;

      if ( container[b].degree !=0 ) {

      int child=container[b].child;

      if ( child==a ) 

	container[b].child=container[child].right_neighbor;

      unlace(a);

      }

      /*Lacing i to the roots.*/

      int right=container[minimum].right_neighbor;

      container[minimum].right_neighbor=a;

      container[a].left_neighbor=minimum;

      container[a].right_neighbor=right;

      container[right].left_neighbor=a;

      container[a].parent=-1;

      container[a].marked=false;

    }

    void cascade (int a) 

    {

      if ( container[a].parent!=-1 ) {

	int p=container[a].parent;

	if ( container[a].marked==false ) container[a].marked=true;

	else {

	  cut(a,p);

	  cascade(p);

	}

      }

    }

    void fuse (int a, int b) 

    {

      unlace(b);

      /*Lacing b under a.*/

      container[b].parent=a;

      if (container[a].degree==0) {

	container[b].left_neighbor=b;

	container[b].right_neighbor=b;

	container[a].child=b;	

      } else {

	int child=container[a].child;

	int last_child=container[child].left_neighbor;

	container[child].left_neighbor=b;

	container[b].right_neighbor=child;

	container[last_child].right_neighbor=b;

	container[b].left_neighbor=last_child;

      }

      ++container[a].degree;

      container[b].marked=false;

    }

    /*

     *It is invoked only if a has siblings.

     */

    void unlace (int a) {      

      int leftn=container[a].left_neighbor;

      int rightn=container[a].right_neighbor;

      container[leftn].right_neighbor=rightn;

      container[rightn].left_neighbor=leftn;

    }

    class store {

      friend class FibHeap;

      Item name;

      int parent;

      int left_neighbor;

      int right_neighbor;

      int child;

      int degree;  

      bool marked;

      bool in;

      PrioType prio;

      store() : parent(-1), child(-1), degree(), marked(false), in(true) {} 

    };

  };

} //namespace hugo

#endif