1 //
2 //=======================================================================
3 // Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
4 // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
5 //
6 // Distributed under the Boost Software License, Version 1.0. (See
7 // accompanying file LICENSE_1_0.txt or copy at
8 // http://www.boost.org/LICENSE_1_0.txt)
9 //=======================================================================
10 //
11 #ifndef BOOST_MUTABLE_QUEUE_HPP
12 #define BOOST_MUTABLE_QUEUE_HPP
13 
14 #include <vector>
15 #include <algorithm>
16 #include <functional>
17 #include <boost/property_map/property_map.hpp>
18 #include <boost/pending/mutable_heap.hpp>
19 #include <boost/pending/is_heap.hpp>
20 #include <boost/graph/detail/array_binary_tree.hpp>
21 #include <iterator>
22 
23 namespace boost {
24 
25   // The mutable queue whose elements are indexed
26   //
27   // This adaptor provides a special kind of priority queue that has
28   // and update operation. This allows the ordering of the items to
29   // change. After the ordering criteria for item x changes, one must
30   // call the Q.update(x)
31   //
32   // In order to efficiently find x in the queue, a functor must be
33   // provided to map value_type to a unique ID, which the
34   // mutable_queue will then use to map to the location of the
35   // item. The ID's generated must be between 0 and N, where N is the
36   // value passed to the constructor of mutable_queue
37 
38   template <class IndexedType,
39             class RandomAccessContainer = std::vector<IndexedType>,
40             class Comp = std::less<typename RandomAccessContainer::value_type>,
41             class ID = identity_property_map >
42   class mutable_queue {
43   public:
44     typedef IndexedType value_type;
45     typedef typename RandomAccessContainer::size_type size_type;
46   protected:
47     typedef typename RandomAccessContainer::iterator iterator;
48 #if !defined BOOST_NO_STD_ITERATOR_TRAITS
49     typedef array_binary_tree_node<iterator, ID> Node;
50 #else
51     typedef array_binary_tree_node<iterator, value_type, ID> Node;
52 #endif
53     typedef compare_array_node<RandomAccessContainer,Comp> Compare;
54     typedef std::vector<size_type> IndexArray;
55   public:
56     typedef Compare value_compare;
57     typedef ID id_generator;
58 
mutable_queue(size_type n,const Comp & x,const ID & _id)59     mutable_queue(size_type n, const Comp& x, const ID& _id)
60       : index_array(n), comp(x), id(_id) {
61       c.reserve(n);
62     }
63     template <class ForwardIterator>
mutable_queue(ForwardIterator first,ForwardIterator last,const Comp & x,const ID & _id)64     mutable_queue(ForwardIterator first, ForwardIterator last,
65                   const Comp& x, const ID& _id)
66       : index_array(std::distance(first, last)), comp(x), id(_id)
67     {
68       while( first != last ) {
69         push(*first);
70         ++first;
71       }
72     }
73 
empty() const74     bool empty() const { return c.empty(); }
75 
pop()76     void pop() {
77       value_type tmp = c.back();
78       c.back() = c.front();
79       c.front() = tmp;
80 
81       size_type id_f = get(id, c.back());
82       size_type id_b = get(id, tmp);
83       size_type i = index_array[ id_b ];
84       index_array[ id_b ] = index_array[ id_f ];
85       index_array[ id_f ] = i;
86 
87       c.pop_back();
88       Node node(c.begin(), c.end(), c.begin(), id);
89       down_heap(node, comp, index_array);
90     }
push(const IndexedType & x)91     void push(const IndexedType& x) {
92       c.push_back(x);
93       /*set index-array*/
94       index_array[ get(id, x) ] = c.size()-1;
95       Node node(c.begin(), c.end(), c.end() - 1, id);
96       up_heap(node, comp, index_array);
97     }
98 
update(const IndexedType & x)99     void update(const IndexedType& x) {
100       size_type current_pos = index_array[ get(id, x) ];
101       c[current_pos] = x;
102 
103       Node node(c.begin(), c.end(), c.begin()+current_pos, id);
104       update_heap(node, comp, index_array);
105     }
106 
front()107     value_type& front() { return c.front(); }
top()108     value_type& top() { return c.front(); }
109 
front() const110     const value_type& front() const { return c.front(); }
top() const111     const value_type& top() const { return c.front(); }
112 
size() const113     size_type size() const { return c.size(); }
114 
clear()115     void clear() { c.clear(); }
116 
117 #if 0
118         // dwa 2003/7/11 - I don't know what compiler is supposed to
119         // be able to compile this, but is_heap is not standard!!
120     bool test() {
121       return std::is_heap(c.begin(), c.end(), Comp());
122     }
123 #endif
124 
125    protected:
126     IndexArray index_array;
127     Compare comp;
128     RandomAccessContainer c;
129     ID id;
130   };
131 
132 
133 }
134 
135 #endif // BOOST_MUTABLE_QUEUE_HPP
136