Cycle detection

int V;
std::vector<std::vector<int>> edges;
std::vector<bool> visited, rec;

bool cycle_dfs(int u)
{
    if(!visited[u])
    {
        visited[u] = rec[u] = true;
        for(int v : edges[u])
            if((!visited[v] && cycle_dfs(v)) || rec[i])
                return true;
        rec[i] = false;
    }
    return false;
}

bool has_cycles()
{
    visited.resize(V, false), rec.resize(V, false);
    for(int u = 0; u < V; u++)
        if(cycle_dfs(u))
            return true;

    return false;
}