Poj1236network of schools (strong connected component + Pinch point)

Topic Link Network of schools

Refer to the Bin God Blog

the indentation of strongly connected components is 0. the number and the degree of 0 Number of components

Main topic: N (2<n<100) There is a one-way network between schools, and each school gets a set of software that can be transmitted to neighboring schools via a one-way network, question 1 : Initially, at least how many schools need to be distributed software, so that all schools in the network will eventually get the software. 2, at least a few transmission lines ( edges)need to be added,so that after any software release to a school, after several transfers, all the schools in the network will eventually get the software.

That is

? given a direction graph, ask:

1) Select at least a few vertices to be able to proceed from these vertices to reach all vertices

2) at least how many edges must be added to allow all vertices to be reached from any vertex

? number of vertices <=

Problem Solving Ideas:

? 1. Find all the strongly connected components

? 2. Each strongly connected component is shrunk to a point, forming a directed acyclic graph Dag.

? 3. What is the number of vertices with a 0 in the DAG above , and the answer to question 1?

Poj1236network of schools (strong connected component + Pinch point)