//

 //=======================================================================

 // Copyright 1997, 1998, 1999, 2000 University of Notre Dame.

 // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek

 //

 // Distributed under the Boost Software License, Version 1.0. (See

 // accompanying file LICENSE_1_0.txt or copy at

 // http://www.boost.org/LICENSE_1_0.txt)

 //=======================================================================

 //

 #ifndef BOOST_MUTABLE_QUEUE_HPP

 #define BOOST_MUTABLE_QUEUE_HPP

 #include <vector>

 #include <algorithm>

 #include <functional>

 #include <boost/property_map.hpp>

 #include <boost/pending/mutable_heap.hpp>

 #include <boost/pending/is_heap.hpp>

 #include <boost/graph/detail/array_binary_tree.hpp>

 #include <iterator>

 namespace boost {

   // The mutable queue whose elements are indexed

   // 

   // This adaptor provides a special kind of priority queue that has

   // and update operation. This allows the ordering of the items to

   // change. After the ordering criteria for item x changes, one must

   // call the Q.update(x)

   // 

   // In order to efficiently find x in the queue, a functor must be

   // provided to map value_type to a unique ID, which the

   // mutable_queue will then use to map to the location of the

   // item. The ID's generated must be between 0 and N, where N is the

   // value passed to the constructor of mutable_queue

   template <class IndexedType, 

             class RandomAccessContainer = std::vector<IndexedType>, 

             class Comp = std::less<typename RandomAccessContainer::value_type>,

             class ID = identity_property_map >

   class mutable_queue {

   public:

     typedef IndexedType value_type;

     typedef typename RandomAccessContainer::size_type size_type;

   protected:

     typedef typename RandomAccessContainer::iterator iterator;

 #if !defined BOOST_NO_STD_ITERATOR_TRAITS

     typedef  adstl::array_binary_tree_node<iterator, ID> Node;

 #else

     typedef  adstl::array_binary_tree_node<iterator, value_type, ID> Node;

 #endif

     typedef  adstl::compare_array_node<RandomAccessContainer,Comp> Compare;

     typedef std::vector<size_type> IndexArray;

   public:

     typedef Compare value_compare;

     typedef ID id_generator;

     mutable_queue(size_type n, const Comp& x, const ID& _id) 

       : index_array(n), comp(x), id(_id) {

       c.reserve(n); 

     }

     template <class ForwardIterator>

     mutable_queue(ForwardIterator first, ForwardIterator last, 

                   const Comp& x, const ID& _id) 

       : index_array(std::distance(first, last)), comp(x), id(_id)

     {

       while( first != last ) {

         push(*first);

         ++first;

       }

     }

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

     void pop() {

       value_type tmp = c.back();

       c.back() = c.front();

       c.front() = tmp;

       size_type id_f = get(id, c.back());

       size_type id_b = get(id, tmp);

       size_type i = index_array[ id_b ];

       index_array[ id_b ] = index_array[ id_f ];

       index_array[ id_f ] = i;

       c.pop_back();

       Node node(c.begin(), c.end(), c.begin(), id);

       down_heap(node, comp, index_array);       

     }

     void push(const IndexedType& x) {

       c.push_back(x);

       /*set index-array*/

       index_array[ get(id, x) ] = c.size()-1;

       Node node(c.begin(), c.end(), c.end() - 1, id);

       up_heap(node, comp, index_array);

     }

     void update(const IndexedType& x) {

       size_type current_pos = index_array[ get(id, x) ];

       c[current_pos] = x;

       Node node(c.begin(), c.end(), c.begin()+current_pos, id);

       update_heap(node, comp, index_array);

     }

     value_type& front() { return c.front(); }

     value_type& top() { return c.front(); }

     const value_type& front() const { return c.front(); }

     const value_type& top() const { return c.front(); }

     size_type size() const { return c.size(); }

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

 #if 0

         // dwa 2003/7/11 - I don't know what compiler is supposed to

         // be able to compile this, but is_heap is not standard!!

     bool test() {

       return std::is_heap(c.begin(), c.end(), Comp());

     }

 #endif 

    protected:

     IndexArray index_array;

     Compare comp;

     RandomAccessContainer c;

     ID id;

   };

 }

 #endif // BOOST_MUTABLE_QUEUE_HPP