Single Points of Failure

Difficulty: 1900 4000 ms 128 MB

graphs

An articulation point is a node whose removal increases the number of connected components. Count them.

Input: the first line has N and M; each of the next M lines has an edge u v.

Output: the number of articulation points.

Constraints:

• 1 ≤ N ≤ 10⁴
• 0 ≤ M ≤ 2×10⁴

Sample Tests

5 5
1 2
2 3
3 1
3 4
4 5

2

2 1
1 2

0

Read the Editorial