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Filename : mutable_queue.hpp
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//
//=======================================================================
// 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/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 array_binary_tree_node< iterator, ID > Node;
#else
    typedef array_binary_tree_node< iterator, value_type, ID > Node;
#endif
    typedef 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