#ifndef GRAPH_H_
#define GRAPH_H_

#include <map>
#include <set>
#include <vector>
#include <utility>

namespace graph {

template<typename V>
class Graph {
public:
  Graph() = default;

  // Add vertex v
  void insert(const V& v);

  // Add edge between v and u
  void insert(const V& v, const V& u);

  // Delete vertex v
  void erase(const V& v);
  
  // Delete edge between v and u
  void erase(const V& v, const V& u);

  // Return true if v and u are connected
  bool connected(const V& v, const V& u);
private:
  std::map<V, std::set<V>> adjacency;
};

template<typename V>
inline void Graph<V>::insert(const V& v) {
  adjacency[v];
}

template<typename V>
inline void Graph<V>::insert(const V& v, const V& u) {
  adjacency[v].insert(u);
}

template<typename V>
inline void Graph<V>::erase(const V& v) {
  adjacency.erase(v);
}

template<typename V>
inline void Graph<V>::erase(const V& v, const V& u) {
  adjacency[v].erase(u);
}

template<typename V>
inline bool Graph<V>::connected(const V& v, const V& u) {
  return true;  
}

} // namespace graph

#endif