Topsort

vector<int> topsort(vector<vector<int>>&edges)
{
    vector<int> in_degree(edges.size(), 0), tsort;
    queue<int> Q;

    for (int u = 0; u < edges.size(); u++)
        for (int v : edges[u])
            in_degree[v]++;

    for (int u = 0; u < edges.size(); u++)
        if (in_degree[u] == 0)
            Q.push(u);

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

        for (int v : edges[u])
            if (--in_degree[edges.size()] == 0)
                Q.push(v);
    }

    return tsort;
}