src/work/jacint/dijkstra.hh
author klao
Thu, 26 Feb 2004 16:07:40 +0000
changeset 132 1ac27e476e25
parent 78 ecc1171307be
permissions -rw-r--r--
makefile: tobb include konyvtar, jobb depend keszites
flow_test.cc: torolve, mert a depend-et megakasztja, igy gondolom nem is fordul
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/*
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 *dijkstra
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 *by jacint
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 *Performs Dijkstra's algorithm from Node s. 
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 *
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 *Constructor: 
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 *
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 *dijkstra(graph_type& G, NodeIt s, EdgeMap& distance)
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 *
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 *
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 *
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 *Member functions:
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 *
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 *void run()
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 *
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 *  The following function should be used after run() was already run.
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 *
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 *
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 *T dist(NodeIt v) : returns the distance from s to v. 
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 *   It is 0 if v is not reachable from s.
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 *
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 *
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 *EdgeIt pred(NodeIt v)
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 *   Returns the last Edge of a shortest s-v path. 
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 *   Returns an invalid iterator if v=s or v is not
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 *   reachable from s.
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 *
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 *
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 *bool reach(NodeIt v) : true if v is reachable from s
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 *
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 *
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 *
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 *
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 *
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 *Problems: 
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 * 
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 *Heap implementation is needed, because the priority queue of stl
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 *does not have a mathod for key-decrease, so we had to use here a 
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 *g\'any solution.
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 * 
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 *The implementation of infinity would be desirable, see after line 100. 
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 */
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#ifndef DIJKSTRA_HH
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#define DIJKSTRA_HH
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#include <queue>
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#include <algorithm>
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#include <marci_graph_traits.hh>
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#include <marciMap.hh>
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namespace std {
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  namespace hugo {
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    template <typename graph_type, typename T>
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    class dijkstra{
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      typedef typename graph_traits<graph_type>::NodeIt NodeIt;
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      typedef typename graph_traits<graph_type>::EdgeIt EdgeIt;
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      typedef typename graph_traits<graph_type>::EachNodeIt EachNodeIt;
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      typedef typename graph_traits<graph_type>::InEdgeIt InEdgeIt;
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      typedef typename graph_traits<graph_type>::OutEdgeIt OutEdgeIt;
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      graph_type& G;
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      NodeIt s;
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      NodeMap<graph_type, EdgeIt> predecessor;
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      NodeMap<graph_type, T> distance;
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      EdgeMap<graph_type, T> length;
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      NodeMap<graph_type, bool> reached;
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  public :
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    /*
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      The distance of all the Nodes is 0.
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    */
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    dijkstra(graph_type& _G, NodeIt _s, EdgeMap<graph_type, T>& _length) : 
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      G(_G), s(_s), predecessor(G, 0), distance(G, 0), length(_length), reached(G, false) { }
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      /*By Misi.*/
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      struct Node_dist_comp
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      {
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	NodeMap<graph_type, T> &d;
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	Node_dist_comp(NodeMap<graph_type, T> &_d) : d(_d) {} 
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	bool operator()(const NodeIt& u, const NodeIt& v) const 
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	{ return d.get(u) < d.get(v); }
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      };
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      void run() {
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	NodeMap<graph_type, bool> scanned(G, false);
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	std::priority_queue<NodeIt, vector<NodeIt>, Node_dist_comp> 
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	  heap(( Node_dist_comp(distance) ));
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	heap.push(s);
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	reached.put(s, true);
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	while (!heap.empty()) {
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	  NodeIt v=heap.top();	
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	  heap.pop();
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	  if (!scanned.get(v)) {
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	    for(OutEdgeIt e=G.template first<OutEdgeIt>(v); e.valid(); ++e) {
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	      NodeIt w=G.head(e);
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	      if (!scanned.get(w)) {
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		if (!reached.get(w)) {
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		  reached.put(w,true);
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		  distance.put(w, distance.get(v)-length.get(e));
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		  predecessor.put(w,e);
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		} else if (distance.get(v)-length.get(e)>distance.get(w)) {
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		  distance.put(w, distance.get(v)-length.get(e));
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		  predecessor.put(w,e);
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		}
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		heap.push(w);
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	      } 
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	    } 
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	    scanned.put(v,true);
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	  } // if (!scanned.get(v))
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	} // while (!heap.empty())
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      } //void run()
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      /*
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       *Returns the distance of the Node v.
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       *It is 0 for the root and for the Nodes not
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       *reachable form the root.
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       */      
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      T dist(NodeIt v) {
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	return -distance.get(v);
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      }
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      /*
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       *  Returns the last Edge of a shortest s-v path. 
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       *  Returns an invalid iterator if v=root or v is not
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       *  reachable from the root.
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       */      
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      EdgeIt pred(NodeIt v) {
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	if (v!=s) { return predecessor.get(v);}
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	else {return EdgeIt();}
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      }
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      bool reach(NodeIt v) {
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	return reached.get(v);
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      }
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    };// class dijkstra
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  } // namespace hugo
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}
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#endif //DIJKSTRA_HH
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