Adding DAG implementation

daggy/include/daggy/DAG.impl

@@ -0,0 +1,59 @@
+template<typename T>
+void DAG<T>::addVertex(T id) {
+  if (vertices.find(id) != vertices.end())
+    throw std::runtime_error("Vertex already exists in graph");
+  vertices.emplace(id, Vertex{});
+  roots.insert(id);
+}
+
+template<typename T>
+void DAG<T>::dropVertex(const T & id) {
+  auto it = vertices.find(id);
+  auto vert = vertices.extract(id);
+  for (auto cid : vert.children) dropEdge(id, cid);
+  for (auto pid : vert.parents) dropEdge(pid, id);
+
+  // Remove anything
+  roots.extract(id);
+}
+
+template<typename T>
+void DAG<T>::dropEdge(const T & from, const T & to) {
+  auto & src = vertices.at(from);
+  auto & dst = vertices.at(to);
+
+  src.children.extract(to);
+  dst.parents.extract(from);
+
+  roots.extract(to);
+}
+
+template<typename T>
+void DAG<T>::addEdge(const T & from, const T & to) {
+  auto & src = vertices.at(from);
+  auto & dst = vertices.at(to);
+
+  // Add the edge
+  src.children.insert(to);
+  dst.parents.insert(from);
+}
+
+template<typename T>
+std::deque<T> DAG<T>::shortest_path(const T & from, const T & to) {
+  std::deque<T> subpath;
+
+  if (from == to) return {to};
+
+  auto & src = vertices.at(from);
+
+  for (const auto & cid : src.children) {
+    auto pth = shortest_path(cid, to);
+    if (subpath.size() == 0 or subpath.size() > pth.size())
+      subpath.swap(pth);
+  }
+
+  subpath.push_front(from);
+
+  return subpath;
+}
+