Tarjan

 public List<List<Integer>> getSCComponents(List<Integer>[] graph)
    {
        V = graph.length;
        this.graph = graph;
        low = new int[V];
        visited = new boolean[V];
        stack = new Stack<Integer>();
        sccComp = new ArrayList<>();

        for (int v = 0; v < V; v++)
              if (!visited[v])
                dfs(v);

        return sccComp;
    }