Find a directed spanning tree in rooted at a node
(2) PostOrder 
(3) For
(4)  For /*Only nodes “downstream”*/
(5)   if and
     /* is the number of descendants
    in the tree including /
(6)       then is 1-link-connected. /*Its removal cuts the graph*/
Algorithm 5: Tarjan-2-link-components , developed by Tarjan [57].