Eulerian Path

struct Edge;
typedef list<Edge>::iterator iter;

struct Edge {
    int next_vertex;
    iter reverse_edge;

    Edge(int next_vertex) : next_vertex(next_vertex) {}
};

const int max_vertices =;
int num_vertices;
list <Edge> adj[max_vertices]; // adjacency list
vector<int> path;

void find_path(int v) {
    while (adj[v].size() > 0) {
        int vn = adj[v].front().next_vertex;
        adj[vn].erase(adj[v].front().reverse_edge);
        adj[v].pop_front();
        find_path(vn);
    }
    path.push_back(v);
}

void add_edge(int a, int b) {
    adj[a].push_front(Edge(b));
    iter ita = adj[a].begin();
    adj[b].push_front(Edge(a));
    iter itb = adj[b].begin();
    ita->reverse_edge = itb;
    itb->reverse_edge = ita;
}