The crux of the algorithm comes in determining whether a node is the root of a strongly connected component. 算法的关键是判断一个结点是否是强连通分量的根。
When a node is identified as the root node, once recursion on its successors has finished, all nodes on the stack from the root upwards form a complete strongly connected component. 当一个结点被确定为一个根时,一旦后续子女递归完成,那么从栈中找到所有的相关结点就是一个完整的强连通分量。
When the search returns from a subtree, the nodes are taken from the stack and it is determined whether each node is the root of a strongly connected component. 当从一个搜索树返回时,判断该点是否是一个强连通分量的根。