improve bfs examples

Author: 64json

algorithm/graph_search/bfs/shortest_path/data.js

@@ -1,5 +1,5 @@
-var tracer = new WeightedDirectedGraphTracer();
+var tracer = new WeightedUndirectedGraphTracer();
 var logger = new LogTracer();
 tracer.attach(logger);
-var G = WeightedDirectedGraph.random(5, 1, 1, 9);
+var G = WeightedUndirectedGraph.random(5, 1, 1, 9);
 tracer._setData(G);