# Validity of list of articulation points in a graph after a node is deleted

Say I have a bidirectional graph G and I have the list of articulation points and bridges of this graph. Say, the list of articulation points is ap[] and the list of bridges are bridges[]. Now, if I remove a node which does not belong to the list of ap[], meaning, this node is not an articulation point and deleting this node will not divide the nodes of this graph into different connected components. Now, do I have to update the list of the articulation points ap[]? I mean after deleting the node, is it possible that some more node(s) in the graph will become articulation points? The same question is for the list of bridges. If I remove an edge which is not a bridge in the graph, after deleting it, is it possible that some more existing edge(s) will become bridge?

• This question is somewhat related; it may be worthwhile to check the sources provided in the answer. – AProgrammer Jun 21 '17 at 14:01
• Learned some new things. Thanks! So is it possible the list of articulation points will be invalid after deleting a node? – Redwanul Sourav Jun 21 '17 at 14:32

• $V=\{1,2,3,4\}$
• $E=\{\{1,2\},\{2,3\},\{3,4\},\{4,1\}\}$