Fix bug that would make ids connect to a different component

algorithm/tarjan.h

@@ -28,6 +28,7 @@ private:
   std::stack<T> S;
   std::int16_t index = 0;
   std::vector<SCC<T>> SCCs;
+  T cid;
 
   struct Vertex {
     int index = -1;
@@ -56,6 +57,7 @@ void Tarjan<T>::strongConnect(const T& u) {
   if (vmap[u].lowlink == vmap[u].index) {
     std::map<T, std::set<T>> scc;
     bool finished = false;
+    cid = S.top();
 
     do {
       const auto w = S.top();
@@ -65,7 +67,7 @@ void Tarjan<T>::strongConnect(const T& u) {
       finished = (w == u);
     } while (!finished);
     
-    SCCs.push_back({ scc, static_cast<T>(vmap[u].lowlink + 1) });
+    SCCs.push_back({ scc, static_cast<T>(cid) });
   }
 }