Add GraphBase::getDegree()

include/aoc/common/GraphBase.hpp

@@ -23,6 +23,7 @@ class GraphBase
 public:
     size_t getNVertices() const;
     size_t getNEdges() const;
+    size_t getDegree(const int vertex) const;
     bool areAdjacent(const int vertex1, const int vertex2) const;
 
     struct Incidence
@@ -51,7 +52,7 @@ class GraphBase
         {
             if (vertex >= 0 && vertex < graph_->getNVertices())
             {
-                setIncidence(graph_->firstVertexIncidences[vertex]);
+                setIncidence(graph_->vertexIncidenceHeaders[vertex].first);
             }
         };
         NeighborIterator& operator++()
@@ -99,7 +100,8 @@ class GraphBase
     NeighborIterator end() const;
 
 protected:
-    std::vector<int> firstVertexIncidences{};
+    // First is the index of the first incidence, second is the number of incidences (the length of the list).
+    std::vector<std::pair<int, size_t>> vertexIncidenceHeaders{};
     std::vector<int> nextIncidences{};
     std::vector<int> incidenceVertices{};
     int addVertexInternal();