1 | // -*- C++ -*- |
---|
2 | |
---|
3 | #ifndef HUGO_DIJKSTRA_H |
---|
4 | #define HUGO_DIJKSTRA_H |
---|
5 | |
---|
6 | ///\file |
---|
7 | ///\brief Dijkstra algorithm. |
---|
8 | |
---|
9 | #include <fib_heap.h> |
---|
10 | #include <bin_heap.h> |
---|
11 | #include <invalid.h> |
---|
12 | |
---|
13 | namespace hugo { |
---|
14 | |
---|
15 | ///%Dijkstra algorithm class. |
---|
16 | |
---|
17 | ///This class provides an efficient implementation of %Dijkstra algorithm. |
---|
18 | ///The edge lengths are passed to the algorithm using a |
---|
19 | ///\ref ReadMapSkeleton "readable map", |
---|
20 | ///so it is easy to change it to any kind of length. |
---|
21 | /// |
---|
22 | ///The type of the length is determined by the \c ValueType of the length map. |
---|
23 | /// |
---|
24 | ///It is also possible to change the underlying priority heap. |
---|
25 | /// |
---|
26 | ///\param Graph The graph type the algorithm runs on. |
---|
27 | ///\param LengthMap This read-only EdgeMap determines the lengths of |
---|
28 | ///the edges. It is read once for each edge, so the map may involve |
---|
29 | ///in relatively time consuming process to compute the edge length |
---|
30 | ///if it is necessary. The default map type is \ref |
---|
31 | ///GraphSkeleton::EdgeMap "Graph::EdgeMap<int>" |
---|
32 | ///\param Heap The heap type used by the %Dijkstra algorithm. The |
---|
33 | ///default is using \ref BinHeap "binary heap". |
---|
34 | |
---|
35 | #ifdef DOXYGEN |
---|
36 | template <typename Graph, |
---|
37 | typename LengthMap, |
---|
38 | typename Heap> |
---|
39 | #else |
---|
40 | template <typename Graph, |
---|
41 | typename LengthMap=typename Graph::EdgeMap<int>, |
---|
42 | template <class,class,class> class Heap = BinHeap > |
---|
43 | #endif |
---|
44 | class Dijkstra{ |
---|
45 | public: |
---|
46 | typedef typename Graph::Node Node; |
---|
47 | typedef typename Graph::NodeIt NodeIt; |
---|
48 | typedef typename Graph::Edge Edge; |
---|
49 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
---|
50 | |
---|
51 | typedef typename LengthMap::ValueType ValueType; |
---|
52 | typedef typename Graph::NodeMap<Edge> PredMap; |
---|
53 | typedef typename Graph::NodeMap<Node> PredNodeMap; |
---|
54 | typedef typename Graph::NodeMap<ValueType> DistMap; |
---|
55 | |
---|
56 | private: |
---|
57 | const Graph& G; |
---|
58 | const LengthMap& length; |
---|
59 | PredMap predecessor; |
---|
60 | PredNodeMap pred_node; |
---|
61 | DistMap distance; |
---|
62 | |
---|
63 | public : |
---|
64 | |
---|
65 | Dijkstra(Graph& _G, LengthMap& _length) : |
---|
66 | G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { } |
---|
67 | |
---|
68 | void run(Node s); |
---|
69 | |
---|
70 | ///The distance of a node from the source. |
---|
71 | |
---|
72 | ///Returns the distance of a node from the source. |
---|
73 | ///\pre \ref run() must be called before using this function. |
---|
74 | ///\warning If node \c v in unreachable from the source the return value |
---|
75 | ///of this funcion is undefined. |
---|
76 | ValueType dist(Node v) const { return distance[v]; } |
---|
77 | |
---|
78 | ///Returns the edges of the shortest path tree. |
---|
79 | |
---|
80 | ///For a node \c v it returns the last edge of the shortest path |
---|
81 | ///from the source to \c v or INVALID if \c v is unreachable |
---|
82 | ///from the source. |
---|
83 | ///\pre \ref run() must be called before using this function. |
---|
84 | Edge pred(Node v) const { return predecessor[v]; } |
---|
85 | |
---|
86 | ///Returns the nodes of the shortest paths. |
---|
87 | |
---|
88 | ///For a node \c v it returns the last but one node of the shortest path |
---|
89 | ///from the source to \c v or INVALID if \c v is unreachable |
---|
90 | ///from the source. |
---|
91 | ///\pre \ref run() must be called before using this function. |
---|
92 | Node predNode(Node v) const { return pred_node[v]; } |
---|
93 | |
---|
94 | ///Returns a reference to the NodeMap of distances. |
---|
95 | |
---|
96 | ///\pre \ref run() must be called before using this function. |
---|
97 | /// |
---|
98 | const DistMap &distMap() const { return distance;} |
---|
99 | |
---|
100 | ///Returns a reference to the shortest path tree map. |
---|
101 | |
---|
102 | ///Returns a reference to the NodeMap of the edges of the |
---|
103 | ///shortest path tree. |
---|
104 | ///\pre \ref run() must be called before using this function. |
---|
105 | const PredMap &predMap() const { return predecessor;} |
---|
106 | |
---|
107 | ///Returns a reference to the map of nodes of shortest paths. |
---|
108 | |
---|
109 | ///Returns a reference to the NodeMap of the last but one nodes of the |
---|
110 | ///shortest paths. |
---|
111 | ///\pre \ref run() must be called before using this function. |
---|
112 | const PredNodeMap &predNodeMap() const { return pred_node;} |
---|
113 | |
---|
114 | ///Checks if a node is reachable from the source. |
---|
115 | |
---|
116 | ///Returns \c true if \c v is reachable from the source. |
---|
117 | ///\warning the source node is reported to be unreached! |
---|
118 | ///\todo Is this what we want? |
---|
119 | ///\pre \ref run() must be called before using this function. |
---|
120 | bool reached(Node v) { return G.valid(predecessor[v]); } |
---|
121 | |
---|
122 | }; |
---|
123 | |
---|
124 | |
---|
125 | // ********************************************************************** |
---|
126 | // IMPLEMENTATIONS |
---|
127 | // ********************************************************************** |
---|
128 | |
---|
129 | ///Runs %Dijkstra algorithm from source node \c s. |
---|
130 | |
---|
131 | ///This method runs the %Dijkstra algorithm from a source node \c s |
---|
132 | ///in order to compute the shortest path to each node. The algorithm |
---|
133 | ///computes - The shortest path tree. - The distance of each node |
---|
134 | ///from the source. |
---|
135 | template <typename Graph, typename LengthMap, |
---|
136 | template<class,class,class> class Heap > |
---|
137 | void Dijkstra<Graph,LengthMap,Heap>::run(Node s) { |
---|
138 | |
---|
139 | NodeIt u; |
---|
140 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) { |
---|
141 | predecessor.set(u,INVALID); |
---|
142 | pred_node.set(u,INVALID); |
---|
143 | } |
---|
144 | |
---|
145 | typename Graph::NodeMap<int> heap_map(G,-1); |
---|
146 | |
---|
147 | Heap<Node,ValueType,typename Graph::NodeMap<int> > heap(heap_map); |
---|
148 | heap.push(s,0); |
---|
149 | |
---|
150 | while ( !heap.empty() ) { |
---|
151 | |
---|
152 | Node v=heap.top(); |
---|
153 | ValueType oldvalue=heap[v]; |
---|
154 | heap.pop(); |
---|
155 | distance.set(v, oldvalue); |
---|
156 | |
---|
157 | { //FIXME this bracket is for e to be local |
---|
158 | OutEdgeIt e; |
---|
159 | for(G.first(e, v); G.valid(e); G.next(e)) { |
---|
160 | Node w=G.head(e); |
---|
161 | |
---|
162 | switch(heap.state(w)) { |
---|
163 | case heap.PRE_HEAP: |
---|
164 | heap.push(w,oldvalue+length[e]); |
---|
165 | predecessor.set(w,e); |
---|
166 | pred_node.set(w,v); |
---|
167 | break; |
---|
168 | case heap.IN_HEAP: |
---|
169 | if ( oldvalue+length[e] < heap[w] ) { |
---|
170 | heap.decrease(w, oldvalue+length[e]); |
---|
171 | predecessor.set(w,e); |
---|
172 | pred_node.set(w,v); |
---|
173 | } |
---|
174 | break; |
---|
175 | case heap.POST_HEAP: |
---|
176 | break; |
---|
177 | } |
---|
178 | } |
---|
179 | } //FIXME this bracket |
---|
180 | } |
---|
181 | } |
---|
182 | |
---|
183 | } //END OF NAMESPACE HUGO |
---|
184 | |
---|
185 | #endif |
---|
186 | |
---|
187 | |
---|