Digraph.h

#ifndef DIGRAPH_H
#define DIGRAPH_H

#include <unordered_set>
#include <vector>

class Digraph {

private:
    const std::size_t _num_vertices;
    std::size_t _num_edges;
    std::vector<std::unordered_set<int>> _adjacency_lists;
    std::vector<std::size_t> _indegree;

public:
    Digraph(std::size_t num_vertices);

    inline std::size_t num_vertices() const noexcept { return _num_vertices; }

    inline std::size_t num_edges() const noexcept { return _num_edges; }

    void add_edge(int v, int w);

    inline std::vector<int> adjacent(int v) const { return {_adjacency_lists[v].begin(), _adjacency_lists[v].end()}; }

    Digraph reverse() const;

    // used in Directed_eulerian_cycle
    inline std::size_t outdegree(int v) const { return _adjacency_lists[v].size(); }

    inline std::size_t indegree(int v) const { return _indegree[v]; }
};

#endif // DIGRAPH_H