From f6b9e7b0341b76bd8f41db3bbf455bde385f12d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Mon, 23 Jun 2025 20:52:16 +0200
Subject: [PATCH] Add GraphBase::getDegree()

---
 include/aoc/common/GraphBase.hpp |  6 ++++--
 src/common/GraphBase.cpp         | 21 ++++++++++++++-------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/include/aoc/common/GraphBase.hpp b/include/aoc/common/GraphBase.hpp
index 93a59e6..5df728b 100644
--- a/include/aoc/common/GraphBase.hpp
+++ b/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();
diff --git a/src/common/GraphBase.cpp b/src/common/GraphBase.cpp
index 56b6bef..e241e2d 100644
--- a/src/common/GraphBase.cpp
+++ b/src/common/GraphBase.cpp
@@ -17,7 +17,7 @@
 
 size_t GraphBase::getNVertices() const
 {
-    return firstVertexIncidences.size();
+    return vertexIncidenceHeaders.size();
 }
 
 size_t GraphBase::getNEdges() const
@@ -25,6 +25,11 @@ size_t GraphBase::getNEdges() const
     return nextIncidences.size() >> 1;
 }
 
+size_t GraphBase::getDegree(const int vertex) const
+{
+    return vertexIncidenceHeaders[vertex].second;
+}
+
 bool GraphBase::areAdjacent(const int vertex1, const int vertex2) const
 {
     auto it = begin(vertex1);
@@ -51,17 +56,19 @@ GraphBase::NeighborIterator GraphBase::end() const
 
 int GraphBase::addVertexInternal()
 {
-    firstVertexIncidences.push_back(-1);
-    return static_cast<int>(firstVertexIncidences.size()) - 1;
+    vertexIncidenceHeaders.push_back({ -1, 0 });
+    return static_cast<int>(vertexIncidenceHeaders.size()) - 1;
 }
 
 void GraphBase::addEdgeInternal(const int vertex1, const int vertex2)
 {
     incidenceVertices.push_back(vertex2);
-    nextIncidences.push_back(firstVertexIncidences[vertex1]);
-    firstVertexIncidences[vertex1] = static_cast<int>(incidenceVertices.size()) - 1;
+    nextIncidences.push_back(vertexIncidenceHeaders[vertex1].first);
+    vertexIncidenceHeaders[vertex1].first = static_cast<int>(incidenceVertices.size()) - 1;
+    vertexIncidenceHeaders[vertex1].second++;
 
     incidenceVertices.push_back(vertex1);
-    nextIncidences.push_back(firstVertexIncidences[vertex2]);
-    firstVertexIncidences[vertex2] = static_cast<int>(incidenceVertices.size()) - 1;
+    nextIncidences.push_back(vertexIncidenceHeaders[vertex2].first);
+    vertexIncidenceHeaders[vertex2].first = static_cast<int>(incidenceVertices.size()) - 1;
+    vertexIncidenceHeaders[vertex2].second++;
 }