Use neighbors to perform DFS on undirected graphs

lib/alg/dfs.js

@@ -4,8 +4,9 @@ module.exports = dfs;
 
 /*
  * A helper that preforms a pre- or post-order traversal on the input graph
- * and returns the nodes in the order they were visited. This algorithm treats
- * the input as undirected.
+ * and returns the nodes in the order they were visited. If the graph is
+ * undirected then this algorithm will navigate using neighbors. If the graph
+ * is directed then this algorithm will navigate using successors.
  *
  * Order must be one of "pre" or "post".
  */
@@ -14,25 +15,27 @@ function dfs(g, vs, order) {
     vs = [vs];
   }
 
+  var navigation = (g.isDirected() ? g.successors : g.neighbors).bind(g);
+
   var acc = [],
       visited = {};
   _.each(vs, function(v) {
     if (!g.hasNode(v)) {
       throw new Error("Graph does not have node: " + v);
     }
 
-    doDfs(g, v, order === "post", visited, acc);
+    doDfs(g, v, order === "post", visited, navigation, acc);
   });
   return acc;
 }
 
-function doDfs(g, v, postorder, visited, acc) {
+function doDfs(g, v, postorder, visited, navigation, acc) {
   if (!_.has(visited, v)) {
     visited[v] = true;
 
     if (!postorder) { acc.push(v); }
-    _.each(g.successors(v), function(w) {
-      doDfs(g, w, postorder, visited, acc);
+    _.each(navigation(v), function(w) {
+      doDfs(g, w, postorder, visited, navigation, acc);
     });
     if (postorder) { acc.push(v); }
   }