// -*- C++ -*-

 /* 

  *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> >

  *

  *Constructor: 

  *

  *Dijkstra(Graph G, LengthMap length)

  *

  *

  *Methods:

  *

  *void run(Node s)

  *

  *T dist(Node v) : After run(s) was run, it returns the distance from s to v. 

  *   Returns T() if v is not reachable from s.

  *

  *Edge pred(Node v) : After run(s) was run, it returns the last 

  *   edge of a shortest s-v path. It is INVALID for s and for 

  *   the nodes not reachable from s.

  *

  *bool reached(Node v) : After run(s) was run, it is true iff v is 

  *   reachable from s

  *

  */

 #ifndef HUGO_DIJKSTRA_H

 #define HUGO_DIJKSTRA_H

 #include <fib_heap.h>

 #include <invalid.h>

 namespace hugo {

   template <typename Graph, typename T, 

     typename Heap=FibHeap<typename Graph::Node, T, 

     typename Graph::NodeMap<int> >, 

     typename LengthMap=typename Graph::EdgeMap<T> >

   class Dijkstra{

     typedef typename Graph::Node Node;

     typedef typename Graph::NodeIt NodeIt;

     typedef typename Graph::Edge Edge;

     typedef typename Graph::OutEdgeIt OutEdgeIt;

     const Graph& G;

     const LengthMap& length;

     typename Graph::NodeMap<Edge> predecessor;

     typename Graph::NodeMap<T> distance;

     typename Graph::NodeMap<bool> reach;

   public :

     /*

       The distance of the nodes is 0.

     */

     Dijkstra(Graph& _G, LengthMap& _length) : G(_G), 

       length(_length), predecessor(_G), distance(_G), reach(_G) { }

     void run(Node s) {

       NodeIt u;

       for ( G.first(u) ; G.valid(u) ; G.next(u) ) {

 	predecessor.set(u,INVALID);

 	distance.set(u,0);

 	reach.set(u,false);

       }

       typename Graph::NodeMap<bool> scanned(G,false);

       typename Graph::NodeMap<int> heap_map(G,-1);

       Heap heap(heap_map);

       heap.push(s,0); 

       reach.set(s, true);

       while ( !heap.empty() ) {

 	Node v=heap.top(); 

 	T oldvalue=heap.get(v);

 	heap.pop();

 	distance.set(v, oldvalue);

 	scanned.set(v,true);

 	OutEdgeIt e;

 	for( G.first(e,v); G.valid(e); G.next(e)) {

 	  Node w=G.head(e); 

 	  if ( !scanned[w] ) {

 	    if ( !reach[w] ) {

 	      reach.set(w,true);

 	      heap.push(w,oldvalue+length[e]); 

 	      predecessor.set(w,e);

 	    } else if ( oldvalue+length[e] < heap.get(w) ) {

 	      predecessor.set(w,e);

 	      heap.decrease(w, oldvalue+length[e]); 

 	    }

 	  }

 	}

       }

     } 

     T dist(Node v) {

       return distance[v];

     }

     Edge pred(Node v) {

       return predecessor[v];

     }

     bool reached(Node v) {

       return reach[v];

     }

   };

 }

 #endif