Well-written editorial!

In problem D, I couldn't understand the following statement: "When we add a segment, we find all segments which intersect with it — that is, all segments that end earlier than it." Can someone explain the solution in more detail?

Observe, the nodes that connect the articulation bridges are the articulation points because if you remove these nodes, then the articulation bridge will be removed and the graph will be disconnected. So, it is ensured that for the i'th node, if dp[i] = 0, then it is an articulation point along with its parent.