Add single vertex contains method and replace vertices field with adjMatrix' keys

algorithm/breadth_first_search.h

@@ -27,8 +27,8 @@ private:
 template<typename T>
 std::map<T, bool> BreadthFirstSearch<T>::initExplore() {
   std::map<T, bool> graphExplore;
-  for (const auto& v : G.vertices) {
-    graphExplore[v] = false;
+  for (const auto& v : G.adjMatrix) {
+    graphExplore[v.first] = false;
   }
   return graphExplore;
 }