Validate input vectors

bnb/incremental_bfs.cpp

@@ -6,6 +6,11 @@
 
 incremental_bfs::incremental_bfs(const graph& g, std::vector<node_id> sources, std::vector<node_id> sinks) 
     : g_(g), sources_(sources), sinks_(sinks), s_(ibfs_subtree(sources, subtree::s, g)), t_(ibfs_subtree(sinks, subtree::t, g)) {
+    assert(!sources.empty());
+    assert(!sinks.empty());
+    assert(sources.size() <= g.num_nodes()/2);
+    assert(sinks.size() <= g.num_nodes()/2);
+
     node_assignments_ = std::vector<subtree>(g.num_nodes(), none);
     for (node_id node : sources) {
         node_assignments_[node-1] = s;