Remove vector in definition of DegreeMatrix (#459)

* Remove `std::vector<int>` in def of `DegreeMatrix`

* Update calculation of degree matrix

* Remove useless line

Author: sbaldu

include/CXXGraph/Graph/Graph_impl.hpp

@@ -545,9 +545,7 @@ shared<DegreeMatrix<T>> Graph<T>::getDegreeMatrix() const {
     const std::vector<std::pair<shared<const Node<T>>, shared<const Edge<T>>>>
         &neighbors = nodePair.second;
 
-    int degree = (int)neighbors.size();
-
-    (*degreeMatrix)[node] = {degree};
+    (*degreeMatrix)[node] = neighbors.size();
   }
 
   return degreeMatrix;

include/CXXGraph/Utility/Typedef.hpp

@@ -249,7 +249,7 @@ using AdjacencyMatrix = std::unordered_map<
 
 template <typename T>
 using DegreeMatrix =
-    std::unordered_map<shared<const Node<T>>, std::vector<int>, nodeHash<T>>;
+    std::unordered_map<shared<const Node<T>>, unsigned int, nodeHash<T>>;
 
 template <typename T>
 using LaplacianMatrix = std::unordered_map<