# source:lemon-0.x/src/hugo/dijkstra.h@548:61898ac9e9dc

Last change on this file since 548:61898ac9e9dc was 542:69bde1d90c04, checked in by Akos Ladanyi, 18 years ago

Set up automake environment.

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1// -*- C++ -*-
2#ifndef HUGO_DIJKSTRA_H
3#define HUGO_DIJKSTRA_H
4
5///\ingroup galgs
6///\file
7///\brief Dijkstra algorithm.
8
9#include <hugo/bin_heap.h>
10#include <hugo/invalid.h>
11
12namespace hugo {
13
15/// @{
16
17  ///%Dijkstra algorithm class.
18
19  ///This class provides an efficient implementation of %Dijkstra algorithm.
20  ///The edge lengths are passed to the algorithm using a
22  ///so it is easy to change it to any kind of length.
23  ///
24  ///The type of the length is determined by the \c ValueType of the length map.
25  ///
26  ///It is also possible to change the underlying priority heap.
27  ///
28  ///\param Graph The graph type the algorithm runs on.
30  ///EdgeMap
31  ///determines the
32  ///lengths of the edges. It is read once for each edge, so the map
33  ///may involve in relatively time consuming process to compute the edge
34  ///length if it is necessary. The default map type is
35  ///\ref GraphSkeleton::EdgeMap "Graph::EdgeMap<int>"
36  ///\param Heap The heap type used by the %Dijkstra
37  ///algorithm. The default
38  ///is using \ref BinHeap "binary heap".
39  ///
40  ///\author Jacint Szabo
41#ifdef DOXYGEN
42  template <typename Graph,
43            typename LengthMap,
44            typename Heap>
45#else
46  template <typename Graph,
47            typename LengthMap=typename Graph::template EdgeMap<int>,
48            template <class,class,class,class> class Heap = BinHeap >
49#endif
50  class Dijkstra{
51  public:
52    typedef typename Graph::Node Node;
53    typedef typename Graph::NodeIt NodeIt;
54    typedef typename Graph::Edge Edge;
55    typedef typename Graph::OutEdgeIt OutEdgeIt;
56
57    typedef typename LengthMap::ValueType ValueType;
58    typedef typename Graph::template NodeMap<Edge> PredMap;
59    typedef typename Graph::template NodeMap<Node> PredNodeMap;
60    typedef typename Graph::template NodeMap<ValueType> DistMap;
61
62  private:
63    const Graph& G;
64    const LengthMap& length;
65    PredMap predecessor;
66    PredNodeMap pred_node;
67    DistMap distance;
68
69  public :
70
71    Dijkstra(const Graph& _G, const LengthMap& _length) :
72      G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { }
73
74    void run(Node s);
75
76    ///The distance of a node from the root.
77
78    ///Returns the distance of a node from the root.
79    ///\pre \ref run() must be called before using this function.
80    ///\warning If node \c v in unreachable from the root the return value
81    ///of this funcion is undefined.
82    ValueType dist(Node v) const { return distance[v]; }
83
84    ///Returns the previous edge of the shortest path tree.
85
86    ///For a node \c v it returns the previous edge of the shortest path tree,
87    ///i.e. it returns the last edge from a shortest path from the root to \c
88    ///v. It is INVALID if \c v is unreachable from the root or if \c v=s. The
89    ///shortest path tree used here is equal to the shortest path tree used in
90    ///\ref predNode(Node v).  \pre \ref run() must be called before using
91    ///this function.
92    Edge pred(Node v) const { return predecessor[v]; }
93
94    ///Returns the previous node of the shortest path tree.
95
96    ///For a node \c v it returns the previous node of the shortest path tree,
97    ///i.e. it returns the last but one node from a shortest path from the
98    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
99    ///\c v=s. The shortest path tree used here is equal to the shortest path
100    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
101    ///using this function.
102    Node predNode(Node v) const { return pred_node[v]; }
103
104    ///Returns a reference to the NodeMap of distances.
105
106    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
107    ///be called before using this function.
108    const DistMap &distMap() const { return distance;}
109
110    ///Returns a reference to the shortest path tree map.
111
112    ///Returns a reference to the NodeMap of the edges of the
113    ///shortest path tree.
114    ///\pre \ref run() must be called before using this function.
115    const PredMap &predMap() const { return predecessor;}
116
117    ///Returns a reference to the map of nodes of shortest paths.
118
119    ///Returns a reference to the NodeMap of the last but one nodes of the
120    ///shortest path tree.
121    ///\pre \ref run() must be called before using this function.
122    const PredNodeMap &predNodeMap() const { return pred_node;}
123
124    ///Checks if a node is reachable from the root.
125
126    ///Returns \c true if \c v is reachable from the root.
127    ///\warning the root node is reported to be unreached!
128    ///\todo Is this what we want?
129    ///\pre \ref run() must be called before using this function.
130    ///
131    bool reached(Node v) { return G.valid(predecessor[v]); }
132
133  };
134
135
136  // **********************************************************************
137  //  IMPLEMENTATIONS
138  // **********************************************************************
139
140  ///Runs %Dijkstra algorithm from node the root.
141
142  ///This method runs the %Dijkstra algorithm from a root node \c s
143  ///in order to
144  ///compute the
145  ///shortest path to each node. The algorithm computes
146  ///- The shortest path tree.
147  ///- The distance of each node from the root.
148  template <typename Graph, typename LengthMap,
149            template<class,class,class,class> class Heap >
150  void Dijkstra<Graph,LengthMap,Heap>::run(Node s) {
151
152    NodeIt u;
153    for ( G.first(u) ; G.valid(u) ; G.next(u) ) {
154      predecessor.set(u,INVALID);
155      pred_node.set(u,INVALID);
156    }
157
158    typename Graph::template NodeMap<int> heap_map(G,-1);
159
160    typedef Heap<Node, ValueType, typename Graph::template NodeMap<int>,
161      std::less<ValueType> >
162      HeapType;
163
164    HeapType heap(heap_map);
165
166    heap.push(s,0);
167
168      while ( !heap.empty() ) {
169
170        Node v=heap.top();
171        ValueType oldvalue=heap[v];
172        heap.pop();
173        distance.set(v, oldvalue);
174
175        { //FIXME this bracket is for e to be local
176          OutEdgeIt e;
177        for(G.first(e, v);
178            G.valid(e); G.next(e)) {
179          Node w=G.bNode(e);
180
181          switch(heap.state(w)) {
182          case HeapType::PRE_HEAP:
183            heap.push(w,oldvalue+length[e]);
184            predecessor.set(w,e);
185            pred_node.set(w,v);
186            break;
187          case HeapType::IN_HEAP:
188            if ( oldvalue+length[e] < heap[w] ) {
189              heap.decrease(w, oldvalue+length[e]);
190              predecessor.set(w,e);
191              pred_node.set(w,v);
192            }
193            break;
194          case HeapType::POST_HEAP:
195            break;
196          }
197        }
198      } //FIXME tis bracket
199      }
200  }
201
202/// @}
203
204} //END OF NAMESPACE HUGO
205
206#endif
207
208
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