diff --git a/gamedata.cpp b/gamedata.cpp
index d3e7d7b..c0e77db 100644
--- a/gamedata.cpp
+++ b/gamedata.cpp
@@ -90,18 +90,21 @@ bool GameData::add_vertex(int x, int y, int r, int colour)
 }
 
 
-// Oh the recursive recursion!
-float GameData::calculate_strength(Vertex* node, unsigned int depth, list<Vertex*>* visited)
+float GameData::calculate_strength(Vertex* node)
 {
-    if (visited == NULL) visited = new list<Vertex*>;
-    visited->push_back(node);
-
-    list<Vertex*> all_nodes = get_colour(node->colour);
+    list<Vertex*> visited;
 
     // Special case - a one-node tree just returns its own score!
+    list<Vertex*> all_nodes = get_colour(node->colour);
     if (all_nodes.size() == 1) return (float)node->score;
 
+    return calculate_strength_r(node, 0, visited);
+}
 
+
+// Oh the recursive recursion!
+float GameData::calculate_strength_r(Vertex* node, unsigned int depth, list<Vertex*>& visited)
+{
     // Find which vertices we need to visit from here
     list<Edge> es = get_vertex_edges(node);
     list<Vertex*> to_visit;
@@ -113,19 +116,25 @@ float GameData::calculate_strength(Vertex* node, unsigned int depth, list<Vertex
 	// if this is true, we haven't visited the vertex on the other end of
 	// this edge yet
 	if (e.a == node &&
-	    find(visited->begin(), visited->end(), e.b) == visited->end())
+	    find(visited.begin(), visited.end(), e.b) == visited.end())
 	{
 	    to_visit.push_back(e.b);
 	}
 	else if (e.a == node &&
-		 find(visited->begin(), visited->end(), e.b) == visited->end())
+		 find(visited.begin(), visited.end(), e.b) == visited.end())
 	{
 	    to_visit.push_back(e.a);
 	}
     }
 
+    visited.push_back(node);
+
     // This is the base case - this node has no unvisited neighbors
-    if (to_visit.empty()) return (float)(node->score) / depth;
+    if (to_visit.empty())
+    {
+	fprintf(stderr, "At a leaf, and score=%f, depth=%d\n", (float)node->score, depth);
+	return (float)(node->score) / depth;
+    }
 
     // Else, iterate through to_visit and visit them all, summing their
     // effective strengths adjusted for depth.
@@ -137,9 +146,8 @@ float GameData::calculate_strength(Vertex* node, unsigned int depth, list<Vertex
 	 cursor != to_visit.end(); cursor++)
     {
 	Vertex* v = *cursor;
-	modscore += calculate_strength(v, depth+1, visited);
+	modscore += calculate_strength_r(v, depth+1, visited);
     }
 
-    if (depth == 0) delete visited;
     return modscore;
 }
diff --git a/gamedata.h b/gamedata.h
index 2666988..563cf3c 100644
--- a/gamedata.h
+++ b/gamedata.h
@@ -29,7 +29,8 @@ class GameData : public Graph
     bool add_vertex(int x, int y, int r, int colour);
 
  private:
-    float calculate_strength(Vertex* node, unsigned int depth = 0, list<Vertex*>* visited = NULL);
+    float calculate_strength(Vertex* node);
+    float calculate_strength_r(Vertex* node, unsigned int depth, list<Vertex*>& visited);
 
     Vertex* current;
     Turn player;