diff -r 69b2d279c8f0 -r ecc1171307be src/work/jacint/reverse_bfs.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/work/jacint/reverse_bfs.h	Mon Feb 16 16:15:58 2004 +0000
@@ -0,0 +1,89 @@
+/*
+reverse_bfs
+by jacint
+Performs a bfs on the out Edges. It does not count predecessors, 
+only the distances, but one can easily modify it to know the pred as well.
+
+Constructor: 
+
+reverse_bfs(Graph& G, NodeIt t)
+
+
+
+Member functions:
+
+void run(): runs a reverse bfs from t
+
+  The following function should be used after run() was already run.
+
+int dist(NodeIt v) : returns the distance from v to t. It is the number of nodes if t is not reachable from v.
+
+*/
+#ifndef REVERSE_BFS_H
+#define REVERSE_BFS_H
+
+#include <queue>
+#include <list_graph.hh>
+
+
+namespace  marci {
+
+  template <typename Graph>
+  class reverse_bfs {
+    typedef typename Graph::NodeIt NodeIt;
+    typedef typename Graph::EachNodeIt EachNodeIt;
+    typedef typename Graph::InEdgeIt InEdgeIt;
+
+
+    Graph& G;
+    NodeIt t;
+    typename Graph::NodeMap<int> distance;
+    
+
+  public :
+
+    /*
+      The distance of the Nodes is n, except t for which it is 0.
+    */
+    reverse_bfs(Graph& _G, NodeIt _t) : G(_G), t(_t), distance(G, G.nodeNum()) {
+      distance.set(t,0);
+    }
+    
+    void run() {
+
+      typename Graph::NodeMap<bool> reached(G, false); 
+      reached.set(t, true);
+
+      std::queue<NodeIt> bfs_queue;
+      bfs_queue.push(t);
+
+      while (!bfs_queue.empty()) {
+
+        NodeIt v=bfs_queue.front();	
+	bfs_queue.pop();
+
+	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
+	  NodeIt w=G.tail(e);
+	  if (!reached.get(w)) {
+	    bfs_queue.push(w);
+	    distance.set(w, distance.get(v)+1);
+	    reached.set(w, true);
+	  }
+	}
+      }
+    }
+
+
+
+    int dist(NodeIt v) {
+      return distance.get(v);
+    }
+
+
+  };
+
+} // namespace marci
+
+#endif //REVERSE_BFS_HH
+
+