Articulation Points - Core idea

Use Tarjan's algorithm with the articulation point condition: a vertex $u$ is an articulation point if it is the root with $\geq 2$ children, or a non-root with a child $v$ where low[v] >= disc[u]. The difference from bridges: $\geq$ instead of $>$.

A vertex is critical if its subtree cannot escape beyond it. Time complexity: $O(V+E)$, same as the bridge algorithm. You compute the same low-link values but check different conditions.