Fix partition constructor

bnb/partition.cpp

@@ -4,9 +4,7 @@
 
 partition::partition(graph& g) : graph_(g) {
     // Assigns all nodes to none
-    for (unsigned int i = 0; i < g.num_nodes(); i++) {
-        node_assignments_[i] = none;
-    }
+    node_assignments_ = std::vector<partition::subgraph>(g.num_nodes(), none);
 
     // Initializes node counting map
     nodes_[sg_a] = 0;