another one

Author: lrvideckis

library/graphs/bridges_cuts/bridge_tree.hpp

@@ -14,11 +14,10 @@
 //! @endcode
 //! @time O(n + m)
 //! @space O(n)
-vector<vi> bridge_tree(const auto& adj, int num_ccs,
+auto bridge_tree(const auto& adj, int num_ccs,
   const vi& br_id, const vi& is_br) {
-  vector<vi> tree(num_ccs);
+  vector<basic_string<int>> tree(num_ccs);
   rep(i, 0, sz(adj)) for (auto [u, e_id] : adj[i]) if (
-    is_br[e_id]) tree[br_id[i]]
-    .push_back(br_id[u]);
+    is_br[e_id]) tree[br_id[i]] += br_id[u];
   return tree;
 }

tests/library_checker_aizu_tests/graphs/two_edge_components.test.cpp

@@ -17,8 +17,7 @@ int main() {
     edges[i] = {u, v};
   }
   auto [num_ccs, br_id, is_br] = bridges(adj, m);
-  vector<vector<int>> bt =
-    bridge_tree(adj, num_ccs, br_id, is_br);
+  auto bt = bridge_tree(adj, num_ccs, br_id, is_br);
   assert(find(begin(br_id), end(br_id), -1) == end(br_id));
   // check correctness of bridge tree
   {