Kosaraju's algorithm

int V;
vector<vector<int>> edges, sccs;
vector<bool> visited;
stack<int> S;

void post_order(int u)
{
    if (!visited[u])
    {
        visited[u] = true;
        for (int v : edges[u])
            post_order(v);
        S.push(u);
    }
}

void Kosaraju()
{
    vector<vector<int>> rev_edges(V);
    visited.assign(V, false);

    for (int u = 0; u < V; u++)
    {
        post_order(u);
        for (int v : edges[u])
            rev_edges[v].push_back(u);
    }

    visited.assign(V, false);
    while (!S.empty())
    {
        int src = S.top(); S.pop();

        if (!visited[src])
        {
            queue<int> Q({ src });
            visited[src] = true;
            sccs.push_back({});

            while (!Q.empty())
            {
                int u = Q.front(); Q.pop();
                sccs.back().push_back(u);

                for (int v : rev_edges[u])
                    if (!visited[v])
                        Q.push(v), visited[v] = true;
            }
        }
    }
}