1 | // -*- C++ -*- |
---|
2 | /* |
---|
3 | *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> > |
---|
4 | * |
---|
5 | *Constructor: |
---|
6 | * |
---|
7 | *Dijkstra(Graph G, LengthMap length) |
---|
8 | * |
---|
9 | * |
---|
10 | *Methods: |
---|
11 | * |
---|
12 | *void run(Node s) |
---|
13 | * |
---|
14 | *T dist(Node v) : After run(s) was run, it returns the distance from s to v. |
---|
15 | * Returns T() if v is not reachable from s. |
---|
16 | * |
---|
17 | *Edge pred(Node v) : After run(s) was run, it returns the last |
---|
18 | * edge of a shortest s-v path. It is INVALID for s and for |
---|
19 | * the nodes not reachable from s. |
---|
20 | * |
---|
21 | *bool reached(Node v) : After run(s) was run, it is true iff v is |
---|
22 | * reachable from s |
---|
23 | * |
---|
24 | */ |
---|
25 | |
---|
26 | #ifndef HUGO_DIJKSTRA_H |
---|
27 | #define HUGO_DIJKSTRA_H |
---|
28 | |
---|
29 | #include <fib_heap.h> |
---|
30 | #include <invalid.h> |
---|
31 | |
---|
32 | namespace hugo { |
---|
33 | |
---|
34 | //Alpar: Changed the order of the parameters |
---|
35 | |
---|
36 | ///Dijkstra algorithm class. |
---|
37 | |
---|
38 | ///This class provides an efficient implementation of Dijkstra algorithm. |
---|
39 | ///The edge lengths are passed to the algorithm using a |
---|
40 | ///\ref ReadMapSkeleton "readable map", |
---|
41 | ///so it is easy to change it to any kind of length. |
---|
42 | /// |
---|
43 | ///The type of the length is determined by the \c ValueType of the length map. |
---|
44 | /// |
---|
45 | ///It is also posible to change the underlying priority heap. |
---|
46 | /// |
---|
47 | ///\param Graph The graph type the algorithm runs on. |
---|
48 | ///\param LengthMap This read-only EdgeMap determines the |
---|
49 | ///lengths of the edges. It is read once for each edge, so the map |
---|
50 | ///may involve in relatively time consuming process to compute the edge |
---|
51 | ///length if it is necessary. |
---|
52 | ///\param Heap The heap type used by the Dijkstra |
---|
53 | ///algorithm. The default |
---|
54 | ///is using \ref BinHeap "binary heap". |
---|
55 | template <typename Graph, |
---|
56 | typename LengthMap=typename Graph::EdgeMap<int>, |
---|
57 | typename Heap=BinHeap<typename Graph::Node, |
---|
58 | typename LengthMap::ValueType, |
---|
59 | typename Graph::NodeMap<int> > > |
---|
60 | class Dijkstra{ |
---|
61 | public: |
---|
62 | typedef typename LengthMap::ValueType ValueType; |
---|
63 | typedef typename Graph::NodeMap<Edge> PredMap; |
---|
64 | typedef typename Graph::NodeMap<Node> PredNodeMap; |
---|
65 | typedef typename Graph::NodeMap<ValueType> DistMap; |
---|
66 | |
---|
67 | private: |
---|
68 | typedef typename Graph::Node Node; |
---|
69 | typedef typename Graph::NodeIt NodeIt; |
---|
70 | typedef typename Graph::Edge Edge; |
---|
71 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
---|
72 | |
---|
73 | const Graph& G; |
---|
74 | const LengthMap& length; |
---|
75 | PredMap predecessor; |
---|
76 | //In place of reach: |
---|
77 | PredNodeMap pred_node; |
---|
78 | DistMap distance; |
---|
79 | //I don't like this: |
---|
80 | // //FIXME: |
---|
81 | // typename Graph::NodeMap<bool> reach; |
---|
82 | // //typename Graph::NodeMap<int> reach; |
---|
83 | |
---|
84 | public : |
---|
85 | |
---|
86 | /* |
---|
87 | The distance of the nodes is 0. |
---|
88 | */ |
---|
89 | Dijkstra(Graph& _G, LengthMap& _length) : |
---|
90 | G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { } |
---|
91 | |
---|
92 | |
---|
93 | void run(Node s); |
---|
94 | |
---|
95 | ///The distance of a node from the source. |
---|
96 | |
---|
97 | ///Returns the distance of a node from the source. |
---|
98 | ///\pre \ref run() must be called before using this function. |
---|
99 | ///\warning If node \c v in unreachable from \c s the return value |
---|
100 | ///of this funcion is undefined. |
---|
101 | ValueType dist(Node v) const { return distance[v]; } |
---|
102 | ///Returns the edges of the shortest path tree. |
---|
103 | |
---|
104 | ///For a node \c v it returns the last edge of the shortest path |
---|
105 | ///from \c s to \c v or INVALID if \c v is unreachable from \c s. |
---|
106 | ///\pre \ref run() must be called before using this function. |
---|
107 | Edge pred(Node v) const { return predecessor[v]; } |
---|
108 | ///Returns the nodes of the shortest paths. |
---|
109 | |
---|
110 | ///For a node \c v it returns the last but one node of the shortest path |
---|
111 | ///from \c s to \c v or INVALID if \c v is unreachable from \c s. |
---|
112 | ///\pre \ref run() must be called before using this function. |
---|
113 | Node predNode(Node v) const { return pred_node[v]; } |
---|
114 | |
---|
115 | ///Returns a reference to the NodeMap of distances. |
---|
116 | |
---|
117 | ///\pre \ref run() must be called before using this function. |
---|
118 | /// |
---|
119 | const DistMap &distMap() const { return distance;} |
---|
120 | ///Returns a reference to the shortest path tree map. |
---|
121 | |
---|
122 | ///Returns a reference to the NodeMap of the edges of the |
---|
123 | ///shortest path tree. |
---|
124 | ///\pre \ref run() must be called before using this function. |
---|
125 | const PredMap &predMap() const { return predecessor;} |
---|
126 | ///Returns a reference to the map of nodes of shortest paths. |
---|
127 | |
---|
128 | ///Returns a reference to the NodeMap of the last but one nodes of the |
---|
129 | ///shortest paths. |
---|
130 | ///\pre \ref run() must be called before using this function. |
---|
131 | const PredNodeMap &predNodeMap() const { return pred_node;} |
---|
132 | |
---|
133 | // bool reached(Node v) { return reach[v]; } |
---|
134 | |
---|
135 | ///Chech if a node is reachable from \c s. |
---|
136 | |
---|
137 | ///Returns \c true if \c v is reachable from \c s. |
---|
138 | ///\warning \c s is reported to be unreached! |
---|
139 | ///\todo Is this what we want? |
---|
140 | ///\pre \ref run() must be called before using this function. |
---|
141 | /// |
---|
142 | bool reached(Node v) { return G.valid(predecessor[v]); } |
---|
143 | |
---|
144 | }; |
---|
145 | |
---|
146 | |
---|
147 | // ********************************************************************** |
---|
148 | // IMPLEMENTATIONS |
---|
149 | // ********************************************************************** |
---|
150 | |
---|
151 | ///Runs Dijkstra algorithm from node \c s. |
---|
152 | |
---|
153 | ///This method runs the Dijkstra algorithm from node \c s in order to |
---|
154 | ///compute the |
---|
155 | ///shortest path to each node. The algorithm computes |
---|
156 | ///- The shortest path tree. |
---|
157 | ///- The distance of each node. |
---|
158 | template <typename Graph, typename LengthMap, typename Heap > |
---|
159 | void Dijkstra<Graph,LengthMap,Heap>::run(Node s) { |
---|
160 | |
---|
161 | NodeIt u; |
---|
162 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) { |
---|
163 | predecessor.set(u,INVALID); |
---|
164 | pred_node.set(u,INVALID); |
---|
165 | // If a node is unreacheable, then why should be the dist=0? |
---|
166 | // distance.set(u,0); |
---|
167 | // reach.set(u,false); |
---|
168 | } |
---|
169 | |
---|
170 | //We don't need it at all. |
---|
171 | // //FIXME: |
---|
172 | // typename Graph::NodeMap<bool> scanned(G,false); |
---|
173 | // //typename Graph::NodeMap<int> scanned(G,false); |
---|
174 | typename Graph::NodeMap<int> heap_map(G,-1); |
---|
175 | |
---|
176 | Heap heap(heap_map); |
---|
177 | |
---|
178 | heap.push(s,0); |
---|
179 | // reach.set(s, true); |
---|
180 | |
---|
181 | while ( !heap.empty() ) { |
---|
182 | |
---|
183 | Node v=heap.top(); |
---|
184 | ValueType oldvalue=heap[v]; |
---|
185 | heap.pop(); |
---|
186 | distance.set(v, oldvalue); |
---|
187 | |
---|
188 | for(OutEdgeIt e(G,v); G.valid(e); G.next(e)) { |
---|
189 | Node w=G.head(e); |
---|
190 | |
---|
191 | switch(heap.state(w)) { |
---|
192 | case Heap::PRE_HEAP: |
---|
193 | // reach.set(w,true); |
---|
194 | heap.push(w,oldvalue+length[e]); |
---|
195 | predecessor.set(w,e); |
---|
196 | pred_node.set(w,v); |
---|
197 | break; |
---|
198 | case Heap::IN_HEAP: |
---|
199 | if ( oldvalue+length[e] < heap[w] ) { |
---|
200 | heap.decrease(w, oldvalue+length[e]); |
---|
201 | predecessor.set(w,e); |
---|
202 | pred_node.set(w,v); |
---|
203 | } |
---|
204 | break; |
---|
205 | case Heap::POST_HEAP: |
---|
206 | break; |
---|
207 | } |
---|
208 | } |
---|
209 | } |
---|
210 | } |
---|
211 | |
---|
212 | } //END OF NAMESPACE HUGO |
---|
213 | |
---|
214 | #endif |
---|
215 | |
---|
216 | |
---|