Add base paper and tarjan's SCC algorithm

graph/graph.h

@@ -0,0 +1,65 @@
+#ifndef GRAPH_H_
+#define GRAPH_H_
+
+#include "vertex.h"
+
+#include <map>
+#include <set>
+#include <vector>
+#include <utility>
+
+namespace graph {
+
+template<typename T>
+class Graph {
+public:
+  Graph() = default;
+
+  // Add vertex v
+  void insert(Vertex<T>& v);
+
+  // Add edge between v and u
+  void insert(Vertex<T> v, Vertex<T> u);
+
+  // Delete vertex v
+  void erase(Vertex<T>& v);
+  
+  // Delete edge between v and u
+  void erase(Vertex<T>& v, Vertex<T>& u);
+
+  // Return true if v and u are connected
+  bool connected(const Vertex<T>& v, const Vertex<T>& u) const;
+
+  // Adjacency matrix representation
+  std::vector<Vertex<T>> vertices;
+};
+
+template<typename T>
+inline void Graph<T>::insert(Vertex<T>& v) {
+  vertices.push_back(v);
+}
+
+template<typename T>
+inline void Graph<T>::insert(Vertex<T> v, Vertex<T> u) {
+  v.edges.push_back(u);
+  vertices.push_back(v);
+}
+
+template<typename T>
+inline void Graph<T>::erase(Vertex<T>& v) {
+  //
+}
+
+template<typename T>
+inline void Graph<T>::erase(Vertex<T>& v, Vertex<T>& u) {
+  //
+}
+
+template<typename T>
+inline bool Graph<T>::connected(const Vertex<T>& v, const Vertex<T>& u) const {
+  return false;
+}
+
+} // namespace graph
+
+#endif

graph/vertex.h

@@ -0,0 +1,36 @@
+#ifndef VERTEX_H_
+#define VERTEX_H_
+
+#include <cstdint>
+#include <compare>
+#include <ostream>
+#include <vector>
+
+namespace graph {
+
+template<typename T>
+class Vertex {
+public:
+  Vertex() = default;
+  Vertex(T v) : v(v) {}
+  
+  T v;
+  std::uint16_t index = -1;
+  std::uint16_t lowlink = -1;
+  bool onStack = false;
+  std::vector<Vertex<T>> edges;
+
+  auto operator<=>(const Vertex&) const = default;
+
+  template<typename T>
+  friend inline std::ostream& operator<<(std::ostream& os, const Vertex<T>& v);
+};
+
+template<typename T>
+inline std::ostream& operator<<(std::ostream& os, const Vertex<T>& vout) {
+  return os << vout.v;
+}
+
+} // namespace graph
+
+#endif