Add contains method for single vertex and hash function for SCCs

include/graph/digraph.h

@@ -24,6 +24,12 @@ public:
 
   // Reverse graph directions
   auto reverse();
+
+  //
+  auto contains(const T& u);
+
+  friend std::ostream& operator<<<>(std::ostream& os, Digraph<T>& G);
+
 };
 
 template<typename T>
@@ -60,6 +66,26 @@ auto Digraph<T>::reverse() {
   return revMatrix;
 }
 
+template<typename T>
+auto Digraph<T>::contains(const T& u) {
+  return this->adjList.count(u);
+}
+
+template<typename T>
+std::ostream& operator<<(std::ostream& os, Digraph<T>& G) {
+  os << "V: " << G.V() << " E: " << G.E() << '\n';
+  for (const auto& u : G.vertices()) {
+    if (!G.adjList[u].empty()) {
+      for (const auto& v : G.adjList[u]) {
+        os << u << "->" << v << ' ';
+      }
+      os << '\n';
+    }
+  }
+  os << '\n';
+  return os;
+}
+
 } // namespace graph
 
 #endif