jacint@173: // -*- C++ -*-
jacint@173: /* 
jacint@211:  *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> >
jacint@173:  *
jacint@173:  *Constructor: 
jacint@173:  *
jacint@211:  *Prim(Graph G, LengthMap weight)
jacint@173:  *
jacint@173:  *
jacint@173:  *Methods:
jacint@173:  *
jacint@211:  *void run() : Runs the Prim-algorithm from a random node
jacint@173:  *
jacint@211:  *void run(Node r) : Runs the Prim-algorithm from node s
jacint@173:  *
jacint@211:  *T weight() : After run(r) was run, it returns the minimum 
jacint@211:  *   weight of a spanning tree of the component of the root. 
jacint@173:  *
jacint@211:  *Edge tree(Node v) : After run(r) was run, it returns the 
jacint@211:  *   first edge in the path from v to the root. Returns 
jacint@211:  *   INVALID if v=r or v is not reachable from the root.
jacint@173:  *
jacint@211:  *bool conn() : After run(r) was run, it is true iff G is connected
jacint@173:  *
jacint@211:  *bool reached(Node v) : After run(r) was run, it is true 
jacint@211:  *   iff v is in the same component as the root
jacint@173:  *
jacint@211:  *Node root() : returns the root
jacint@173:  *
jacint@173:  */
jacint@173: 
jacint@211: #ifndef HUGO_PRIM_H
jacint@211: #define HUGO_PRIM_H
jacint@173: 
jacint@173: #include <fib_heap.h>
jacint@211: #include <invalid.h>
jacint@173: 
jacint@173: namespace hugo {
jacint@173: 
jacint@173:   template <typename Graph, typename T, 
jacint@211:     typename Heap=FibHeap<typename Graph::Node, T, 
jacint@211:     typename Graph::NodeMap<int> >, 
jacint@211:     typename LengthMap=typename Graph::EdgeMap<T> >
jacint@173:     class Prim{
jacint@211:       typedef typename Graph::Node Node;
jacint@173:       typedef typename Graph::NodeIt NodeIt;
jacint@211:       typedef typename Graph::Edge Edge;
jacint@173:       typedef typename Graph::OutEdgeIt OutEdgeIt;
jacint@173:       typedef typename Graph::InEdgeIt InEdgeIt;  
jacint@173: 
jacint@211:       const Graph& G;
jacint@211:       const LengthMap& edge_weight;
jacint@211:       typename Graph::NodeMap<Edge> tree_edge;
jacint@173:       typename Graph::NodeMap<T> min_weight;
jacint@211:       typename Graph::NodeMap<bool> reach;
jacint@173:           
jacint@173:   public :
jacint@173: 
jacint@211:       Prim(Graph& _G, LengthMap& _edge_weight) : 
jacint@211: 	G(_G), edge_weight(_edge_weight), 
jacint@211: 	tree_edge(_G,INVALID), min_weight(_G), reach(_G, false) { }
jacint@173: 
jacint@211: 
jacint@211:       void run() {
jacint@211: 	NodeIt _r;	
jacint@211: 	G.first(_r);
jacint@211: 	run(_r);
jacint@173:       }
jacint@173: 
jacint@173: 
jacint@211:       void run(Node r) {
jacint@211: 
jacint@211: 	NodeIt u;
jacint@211: 	for ( G.first(u) ; G.valid(u) ; G.next(u) ) {
jacint@211: 	  tree_edge.set(u,INVALID);
jacint@211: 	  min_weight.set(u,0);
jacint@211: 	  reach.set(u,false);
jacint@211: 	}
jacint@211: 
jacint@173: 
jacint@173: 	typename Graph::NodeMap<bool> scanned(G, false);
jacint@173: 	typename Graph::NodeMap<int> heap_map(G,-1);
jacint@173: 	
jacint@173: 	Heap heap(heap_map);
jacint@173: 
jacint@173: 	heap.push(r,0); 
jacint@211: 	reach.set(r, true);
jacint@173: 
jacint@173: 	while ( !heap.empty() ) {
jacint@173: 
jacint@211: 	  Node v=heap.top(); 
jacint@173: 	  min_weight.set(v, heap.get(v));
jacint@173: 	  heap.pop();
jacint@173: 	  scanned.set(v,true);
jacint@173: 
jacint@173: 	  OutEdgeIt e;
jacint@211: 	  for( G.first(e,v); G.valid(e); G.next(e)) {
jacint@211: 	    Node w=G.head(e); 
jacint@173: 	    
jacint@211: 	    if ( !scanned[w] ) {
jacint@211: 	      if ( !reach[w] ) {
jacint@211: 		reach.set(w,true);
jacint@211: 		heap.push(w, edge_weight[e]); 
jacint@173: 		tree_edge.set(w,e);
jacint@211: 	      } else if ( edge_weight[e] < heap.get(w) ) {
jacint@173: 		tree_edge.set(w,e);
jacint@211: 		heap.decrease(w, edge_weight[e]); 
jacint@173: 	      }
jacint@173: 	    }
jacint@173: 	  }
jacint@173: 
jacint@173: 	  InEdgeIt f;
jacint@211: 	  for( G.first(f,v); G.valid(f); G.next(f)) {
jacint@211: 	    Node w=G.tail(f); 
jacint@173: 	    
jacint@211: 	    if ( !scanned[w] ) {
jacint@211: 	      if ( !reach[w] ) {
jacint@211: 		reach.set(w,true);
jacint@211: 		heap.push(w, edge_weight[f]); 
jacint@173: 		tree_edge.set(w,f);
jacint@211: 	      } else if ( edge_weight[f] < heap.get(w) ) {
jacint@173: 		tree_edge.set(w,f);
jacint@211: 		heap.decrease(w, edge_weight[f]); 
jacint@173: 	      }
jacint@173: 	    }
jacint@173: 	  }
jacint@173: 	}
jacint@173:       } 
jacint@173:  
jacint@173: 
jacint@173:       T weight() {
jacint@173: 	T w=0;
jacint@211: 	NodeIt u;
jacint@211: 	for ( G.first(u) ; G.valid(u) ; G.next(u) ) w+=min_weight[u];
jacint@173: 	return w;
jacint@173:       }
jacint@173:      
jacint@173: 
jacint@211:       Edge tree(Node v) {
jacint@211: 	return tree_edge[v];
jacint@173:       } 
jacint@173: 
jacint@173: 
jacint@173:       bool conn() {
jacint@173: 	bool c=true;
jacint@211: 	NodeIt u;
jacint@211: 	for ( G.first(u) ; G.valid(u) ; G.next(u) ) 
jacint@211: 	  if ( !reached[u] ) { 
jacint@173: 	    c=false;
jacint@173: 	    break;
jacint@173: 	  }
jacint@173: 	return c;
jacint@173:       }
jacint@173: 
jacint@173: 
jacint@211:       bool reached(Node v) {
jacint@211: 	return reached[v];
jacint@173:       }
jacint@173: 
jacint@173: 
jacint@211:       Node root() {
jacint@173: 	return r;
jacint@173:       }
jacint@173: 
jacint@173:     };
jacint@173: 
jacint@173: }
jacint@173: 
jacint@173: #endif
jacint@173: 
jacint@173: